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PHYLUM NEMATHELMINTHES OR ASCHELMINTHES

 

Nematoda
Aphasmidia	Phasmidia
Order- Trichocephalida	Order- 1. Rhabditida
	2. Strongylida
	3. Ascaridida
	4. Spirurida

 

Class – Nematoda

 

General Characters – Body is unsegmented, cylindrical and elongated in shape. The body tapers at both anterior and posterior end. The body is covered with a tough transparent cuticle. The body cavity and alimentary canal are present. The sexes are separate; generally the male is smaller than the female. The length measures from a few millimeters to several meters.

 

Body wall – Body wall consists of 3 different layer (a) Cuticle (b) Subcuticle (hypodermis) and (c) Musculature. The cuticle is very tough and covers the outer body and is also continuous into the mouth and pharynx anteriorly and cloaca or rectum posteriorly. The cuticle consists of 3 layers (i) Cortical layer (2) Matrix layer and (3) Fibrous layer. The sub cuticle lies below the cuticle and is also called hypodermis. It has four longitudinal cords; one in dorsal, one ventral and 2 in the lateral side. The lateral longitudinal cords carry the excretory canal. The musculature layer consists of a number of cells and according to their number, size and arrangement of each cell the class Nematoda may be classified into 3 groups:

 

1. Polymyrian – The cells are numerous and project deep into the body cavity e.g. Ascaridae.
2. Meromyrian – Cells are few in number only 2-3 cells are found in group but they are large in size e.g. family Oxyuridae and Ancylostomatidae.
3. Holomyrian – Cells are numerous, closely packed, small in size e.g. family Trichuridae.

 

The cuticle bears number of special structures which are of taxonomic value. Terms used in the description of Nematodes are:

1. Cuticula – An outer hyaline, non-cellular layer forming the integument of Nematode.
2. Lips – Which is cuticular, surrounds the mouth openings and mostly is found in Ascarian parasite. Out of these one is dorsal and two are ventral. They may be supplied with sensory papillae.
3. Head bulbs – The anterior thickest part such as in Gnathostoma sp. Four cuticular bulbs lie together and are called as head bulbs.
4. Amphids – Pair of depression present in the cephalic region of the parasite. These are chemoreceptor in nature.
5. Phasmids – Pair of sensory papillae present behind the anus.
6. Alae – Cuticular extention of parasite are as follows:
   1. Cervical alae – Wing like expansion of the cuticula near mouth
   2. Caudal alae – Towards the posterior part of the body
   3. Lateral and longitudinal – Present along the entire length of the body.
7. Cervical papillae – Protuberance of cuticula near oesophagus.
8. Buccal capsule – When the oral aperture head to a mouth cavity; it may contain teeth or cutting organ.
9. Cloaca – A common passage in male Nematodes where the rectum and the genital ducts open.
10. Filariform larvae – The oesophagus is long compared to the length of the larva; its posterior end is not dilated like a bulb.
11. Rhabditiform larva – The length of the oesophagus is short compared to the length of the larva and its posterior end is dilated like a bulb.
12. Spicule – Represents the accessory copulatory organ. It is rod like and protrusible. Spicules may be single or in pairs.
13. Copulatory Bursa – An umbrella like expansion of the cuticula surrounded by the cloaca of the male Nematode of certain species. It is supported by fleshy rays, which are comparable with the ribs of an umbrella.

 

Digestive system – It consists (a) mouth opening (b) Buccal capsule  (c) muscular pharynx (d) muscular oesophagus and (e) intestine and Anus or cloaca. The intestine is tubular and is single layered. In case of male parasite the opening of the intestine and reproductive system is the same. This opening is known as cloaca. In case of female both these opening are separate, intestinal opening is called anus and reproductive opening is called vulva. The intestine ends in the rectum. In case of Nematodes the muscular oesophagus is two types:

1. Rhabditiform Oesophagus: It is found in the 1^st larval stages and non-parasitic Nematodes as well as parasitic Nematodes. The oesophagus contains club shaped anterior portion and bulb like posterior portion which are both joint by a narrow neck.
2. Filariform oesophagus –These are found in the second and third stage larva mostly which are in the infective stages and this consists of only club shaped anterior portion.

 

Nervous system – Consists of a nerve ring present at the anterior part at the level of the oesophagus. From the nerve ring 6 nerves turn along forward and backward. There are with sensory organ such as amphids, phasmid and other sensory organs.

 

Excretory system – Flame cells absent, excretory system consists of two excretory lateral excretory canals which run forward and open at the anterior part of the body.

 

Circulatory system - The body contains oxyhaemoglobin which fulfills the function of blood.

 

Reproductive System – Sexes are separate.

1. Male – Has a single testis from which a vasa-deferens arises which gives rise to a seminal vesicle and this is followed by muscular ejaculatory duct which opens in cloaca. Besides this some accessory reproductive organs are also present.

 

1. 1. Spicules: The spicules are chitinised rod like structures, which are present on dorsal wall of the intestine and open into the cloaca. The spicules may be one as in case of Oxyuris or it may two in number (in Ascaris). The most important function of spicules are (a) It helps in holding the female during copulation  (b) To expand the genital opening of female  (c) It acts as a gutter for the transportation of sperm and excites the female during copulation.
   2. Gubernaculam – It is a chitinised structure present on the dorsal wall of the cloaca and guides the spicules during copulation.
   3. Telamon – It is a partially chitinised structure present on the ventral wall of the cloaca and it also guides the spicules during copulation.

Besides these structures; males belonging the the spp. Strongyloides have a cuticular umbrella like expansion at the posterior end called  as copulatory bursa and this helps the union of male and female during copulation. The parasites having bursa are generally called bursates and the bursa is supported by a number of rags.

 

b. Female – The female genital system may be single as in Trichinella spiralis or it may be double in other cases. It consists of a single thread like tubular ovary from which the oviduct arises and is followed by receptaculum seminalis in which spermatozoa are stored and where fertilization takes place. This is followed by uterus, in which egg shells are formed and embryo may develop. The uterus of both the sides join together to form a common tube called as ovijector and this continues as vagina. The genital opening is not common with the intestinal opening of the female, both are separate. According to arrangement of the uterus it is of three types:

1. Prodelph type – In this case both uteri and ovaries run forward.
2. Amphidelph –    The uteri run in opposite directions.
3. Opisthodelph – The uteri run in backward direction.

 

Development of Nematodes- The Nematodes may be oviparous, ovoviviparous or viviparous. There are two types of larvae:

1. Rhabditiform larvae – It is 1^st stage larva of non-parasitic larva or free living larva. In this the esophagus is Rhabditiform
2. Filariform larvae – Infective larvae. Mostly larvae and ex-sheathed larvae or club shaped larvae. Mostly the third stage larvae are under this group. But sometimes the 2^nd form larva is also filariform. It contains filariform oesophagus.

 

Apart from these larvae another larva is Microfilaria. It is the larvae of Filarial parasite.

 

Development – The eggs pass out in the faces to the outside. The embryonic mass divides into 2, 4, 8, 16, 64 cell divisions and so on. This stage is known as Blastomere stage. Then the embryo passes through the morula stage and tadpole larva stage. Then the 1^st stage larvae are present inside the egg. This type of development mostly is found inside the Ascaris parasite. When the definite host ingests the egg containing the 2^nd stage larva, it becomes infected. In the other case; there is production of the 1^st stage larva, then the 2^nd stage which finally moults to the 3^rd stage larvae. The definite host is infected by ingesting the 3^rd stage larvae.

 

Class – Nematoda

Sub class – Secernentea (Phasmidia) Dougher, 1958

Order – Rhabditida

Super family - Rhabditoidea

 

Family 1 - Strongyloididae

Genus- Strongyloides

• Parasites are commonly called as Strongyloides

Species S. papillosa     S. intestine of sheep, goat and cattle, size 3.5-6 mm long & 0.05-

                                    0.06mm wide, egg – 40-60 by 20 µm in diameter

            S. westeri         S. intestine of horse, pig, up to 9 mm long & 0.8-0.9mm wide, egg    

                                   40-52 by 32-40 µm in diameter.

    S. stercoralis            S. intestine of dog, fox, cat and man, size 2.2 mm long &   0.03 mm wide       

    S. ransomi               S. intestine of pig, size 3.33-4.49 mm long, egg 40-55 by 26-50µm

    S. avium                  S. intestine and caeca of fowl, egg 52-56 by 36-40 µm in diameter.

 

Fig. Strongyloides spp.

Morphology – Small parasite measuring about 3-5 mm. Two forms of parasite are found:

 

(a) Non parasitic form or free living form - In this case the oesophagus is rhabditiform type and esophageal bulb is present and in case of females the vulva is situated near the middle of the body.

b) Parasitic form- In this case esophagus is regularly rhabditiform but no esophageal bulb is present, so called filiariform type of esophagus.

 

Eggs – Eggs are oval in shape, transparent, shell is thin when the eggs are passed out through the feces, and the egg contains a well-developed larva with a bifid tail.

 

Life cycle - Eggs are passed out in the feces with well-developed larva. Eggs hatch outside and the 1^st stage larva comes out within a few hours. The 1^st stage larva moults into the 2^nd stage then 3^rd stage larva. After this the life cycle is 2 types.

 

1. Parasitic type – The 3^rd stage larvae when ingested through contaminated pasture or feed may penetrate through the mucosa of the host. Through blood circulation they reach the lungs. From lungs they reach the pharynx. Passing through bronchioles, bronchi and trachea, they are then swallowed and reach the intestine where they become adult.
2. Non parasitic form – The third stage larva may develop into adult males or females in the soil and feed on soil metabolites. Copulation takes place between them in the soil and eggs are passed out. These eggs again hatch and develop into the 3^rd stage larva.
3. Apart from these two types of infection through the oral and percutaneous route, there is another type of infection which may occur which is called as auto-infection. This infection occurs when the eggs hatch in the large intestine. The 3^rd stage infective larva develops which is passed out in the feces. Out of these larvae some may remain attached in the perianal region and they may penetrate the skin near the perianal region thereby causing infection.
4. Hyper-infection- In this case eggs hatch in the small intestine and larvae develop to the 3^rd stage. They penetrate the intestinal wall and through circulation reach the lungs, pharynx and again settle in the intestine.
5. Prenatal infection – Larvae enter into the blood circulation and some reach to the foetus to the developing young animal. Neonatal and transmammary, infection also occurs.

 

Morphology of Infective Larvae (En-Sheathed Larvae)

1. 1. Protective sheath is absent.
   2. Oesophagus is very long and about 1/3 of entire body length.
   3. Tail is bifid.
   4.  

Pathogenesis and Symptoms – Parasitic infestation produces intestinal irritation resulting in diarrhoea, loss of body wt, loss of appetite etc. These are slightly pathogenic to young animals. S. papillosus transmits Foot-rot (Bacterial disease). There is formation of Fusiformis Necrophones during penetration through the skin at foot region. A protein losing enteropathy is also sometimes seen in piglets.

 

Diagnosis – By finding the eggs in the feces.

Treatment –

1. Sheep, Goat and Cattle
   1. Thiabendazole 50 mg/kg b.wt. in pig highly effective 75 mg/kg b.wt. for sheep
   2. Methyridine – 118 mg/kg b.wt. S/c
   3. Haloxan – 30 – 35 mg/kg b.wt.
   4. Levamisole – 5 – 10 mg/kg
   5. Fenbendazole – 50 mg/kg is also highly effectives
2. Pig
   1. Gention violet – 50 – 70 mg/kg b.wt. Twice daily 3 days
   2. Thaibendazole – 50 mg/kg b.wt.
3. Dog
4. Gention violet – 65 mg/kg b.wt. thrice daily – 3 days
5. Diethylcarbamazine – 75-100 mg/kg b.wt.
6. Thibendazole – 50-75 mg/kg is highly effective
7. Albendazole – 7.5 mg/kg b.wt.

 

Order – Strongylida

Super family- Strongyloidea

Family 1– Strongylidae

 

General Morphology – Parasites are commonly called as Strongyles. The important character is that male possesses copulatory bursa at the posterior end of the body. Hence these parasites are commonly called Bursate. Eggs of all parasites belonging to this family are nearly similar. Hence it is difficult to identify the species of parasite from the eggs. The eggs are called the Strongyle egg (Bursate eggs).

 

The copulatory bursa has 3 lobes which are dorsal lobe and 2 lateral lobes and the bursal rays are arranged in 3 system:

1. Ventral system: Which contains ventro-ventral ray and latero-ventral rays.
2. Lateral system – Contain 3 rays in each side
   1. 1. Antero – lateral rays
      2. Medilo – lateral rays
      3. Postero – lateral rays
3. Dorsal system – Contains 2 externo-dorsal and one dorsal ray which may be branched bifid at the tip.

Arrangement of bursal ray is different from species to species. Apart from this the male parasite also has spicules, gubernaculum and telamon. The common characteristic of the egg of Strongyle species are that it is oval shaped, thin shelled and transparent. While it is passed out through feces the embryo may have 2-64 cell divisions.

 

Genus – Strongylus – All spp. belonging to this genus are found in the caecum and colon of horse, mule and asses.

 

 

 

 

Spp. S. equinus

Spp.  S. edentatus

Spp. S. vulgaris

Characters

	S. equinus	S. edentatus	S. vulgaris
Size	Male – 22-26  mm Female – 38-47 mm and 2mm thick.	Male  23-28 mm, Female – 33-44mm and 2mm thick.	Male 14-16 mm Female-20-24 mm and 1.4 mm thick.
Head end	Not marked off	Wider than rest of body	Not marked
Buccal capsule	Oval. At base presence of large dorsal teeth with bifid tips and two small subventral teeth.	Wide anteriorly than at the middle. Teeth are absent.	Oval. Contains two ear shaped dorsal teeth at base.
Host site	Caecum and Colon of equines including zebra.	Found in the large intestine of equines.	Large intestine of equines.

 

Apart from these characters all the three species have a cuticular lip like structure around the mouth opening known as leaf crowns or Corona Radiata. These leaf crowns are of two types (a) External leaf crowns are present which surrounds the mouth opening.  

(b) Internal leaf crown, which are present in the inner margin of the buccal capsule.

In case of female the vulva opens near the posterior end of uterus which is amphidelph type.

 

Life Cycle- There has been various controversies over the life cycle of Strongylys species as it is slightly different. In S.vulgaris infective larva penetrate the intestinal wall, where about eight days after infection 4^th stage larva develop. Such fourth stage forms penetrate the intima of the submucosal arteries and migrate in these vessels to the cranial mesenteric arteries. They are to be found there from the 14^th day of infection onwards and are associated with thrombi and aneurysms. Starting from about the 45^th day of infection the fourth stage larva pass back via the arterial system to the submucosa of the caecum and colon and there become the 5^th stage larva in about 3months of infection. Then they enter the lumen and reach maturity, egg production occurring about six to seven months after infection.

 

Larvae of Strongylus Parasite- At about 26ºc a first stage larva is produced within 20-24 hours; this hatches from the egg to become a free-living stage. Development to the 1^st larval stage may be inhibited by several factors, temperature and lack of moisture being the major ones. The 1^st stage larva has a Rhabditiform esophagus. The larva feeds and then goes to a resting stage and then moults to become the 2^nd stage larva. The 2^nd stage larva repeats the same feeding and resting stage, but instead of completely moulting off, it leaves the old cuticle as a sheath rour. This sheathed third stage larva is the only infective stage that can infect a new host. It does not feed and exists on the reserve food granules present on its intestinal cells. The larva does not actively enter the host, but is ingested with herbage. Its habits are such that it increases the possibility of finding a host some of which are:

1. The larva is negatively geotropic and it crawls up the blades of grass or other herbages.
2. It is positively phototrophic to mild light, but is repelled by strong light. The larva will crawl up on blades of grass in the early morning or in the evening or in dull days. At night time the larvae will crawl down and only a small film of water will suffice for the larvae to climb.
3. There is a certain amount of response to heat; migration is more active in warm weather than in the cold.

Animals are infected while they are grazing in the infected pasture.

Pathogenesis and Symptoms- The disease is known as Strongylosis in case of equine. Adult parasites are present in the caecum and colon and they attach with the caecal wall and suck blood. If heavy infection there is anaemia and sometimes fatal haemorrhages also occurs. The larvae of the 4^th and the 5^th stage produce more pathogenic effects during their migration. On the wall of the caecum and colon they produce nodules in case of S.equine and in case of S. vulgaris these larvae migrate into the cranial mesenteric artery and produce thrombi (blood clot). Detachment of the Strongylus in the cranial mesenteric artery may cause death or paralysis of the animal, because the detached piece of Strongylus may block some important artery which supplies the brain or heart. Apart from these there is loss of appetite, loss of condition, celiac pain, peritonitis, Jaundice and fever may occur. These parasites are highly pathogenic to young animals. In these animals soft and foul smelling diarrhea is observed. In heavy infections there may be death.

 

Diagnosis- By finding the eggs in the feces.

 

Treatment –Phenothiazin-30-35 gm/horse

                     Piperazine compound- 200mg/kg b.wt.

                     Thiabendazole- 44mg/kg b.wt.

                     Mebendazole- 10mg/kg bowt.

                     Fenbendazole- 7.5mg/kg b.wt.

 

 

Family 2-Trichonematidae

 Genus 1- Oesophagotomum

Species- columbianum (nodular worm of sheep, goat, camel and wild antelopes)

 

Location and Host- Occurs in the colon of sheep, goat, camel and a number of wild Antelopes.

Morphology- Males are 12-17mm long and females are 14-25mm long. The cuticle at the anterior end forms a mouth collar, which is separated by a constriction from the rest of the body. There is a cervical groove at the anterior part of the body on the ventral side. The cuticle anterior to this groove forms the cephalic vesicle. Anterior end has large cervical alae, which starts from cervical groove and the anterior part of the cervical alae has two cervical papillae. External and internal leaf crowns are present. Male parasite has well-developed bursa and has two equal wing like alate spicules. The tail of the female tapers to a fine point. The vulva is situated anterior to the anus. The vagina is very short and transverse. The eggs have thin shell and are laid in the 8-16 celled stages.

Genus 2.Oesophagostomum venulosum: This parasite occurs in the caecum and colon of sheep and goat. The cervical alae is absent, cervical papillae is present behind the esophagus.

Genus 3. O.radiatum: Adult parasite is mostly found in the colon of cattle. Its mouth collar is round in shape and cephalic vesicle is constricted behind the middle.

 

Genus 4- O. dentatum

 

Location and Host: Parasite is found in the caecum and colon of pigs.

 

Morphology: Cervical alae are absent and cervical papillae are present towards the posterior side of esophagus.

 

Life Cycle- Eggs are passed out in the feces, the first stage larva hatch out and moult into the 2^nd stage and then third stage infective larvae within 5-6 days. These infective larvae are ingested by host through contaminated food and water. They ex-sheath in the small intestine and the larvae penetrate the wall of the intestine anywhere from duodenum to anus. They moult into the 4^th stage larvae in the intestinal wall and return back to the lumen of intestine. Then they reach to the caecum and colon, moult into the 5^th stage larvae and become adult parasite within 40 days.

 

Pathogenesis and Symptoms- Pathogenesis can be seen in case of lamb and old animals in which there is no immunity developed against the parasite. The parasite does not produce much change in the caecum and colon wall unless there are a large number of adult parasites found. Adult worms do not suck blood but they produce changes in the thickening of the wall of caecum and colon. But in those animals which have some immunity developed against parasite e.g., in those animals which were previously infected with the parasite, marked tissue reactions occur in the wall of the caecum and colon during the migration of larval stages. As a result of this large number of larvae they produce nodules on the wall of the caecum and colon. When the larvae penetrate the intestinal wall due to previous resistance of the host against the parasite, tissue reaction occurs and the larvae are surrounded by Leucocytes especially Eosinophils and Foreign body, Giant cells and become capsulated by Fibroblast and thus nodules are formed. The larvae may remain inside these nodules for about three months after which they may die and the nodules are calcified. This nodular condition in the intestine or the nodules present in the intestine is called as “Pimpy gut” or “Knotty gut”. These nodules sometimes contain greenish yellow pus like material. In heavy infection e.g., if 200-500 parasite are present they may cause death of young animals. Symptoms are Greenish diarrhea mixed with mucus and blood. During acute condition the tail of the animals may remain in raised condition which is followed by death. In mild condition- weakness, skin becomes dry with coarse wool and atrophy of muscles occurs.

 

Diagnosis- From the symptoms, by finding the eggs in the feces or by larval culture. The 3^rd stage infective larvae have a very large tail and the tail end is pointed.

 

Treatment- Phenothiazine- 600- 700mg/kg b.wt.

                     Thiabendazole- 50mg/kg b.wt.

                     Piprazine compound- 125mg/kg b.wt.

 

 

Genus 5- Chabertia ovina

 

Location and Host- Adult parasite is found in the colon of sheep, goat, cattle and a number of other ruminants throughout the world.

 

Morphology- Males are 13-14 mm long and females 17-20mm long. The anterior end is curved slightly ventrally and the large buccal capsule opens antero-ventrally. The oral aperture is surrounded by a double row of small cuticular elements representing the leaf crowns. There is a shallow ventral cervical groove and anterior to it a slightly inflated cephalic vesicle. In the male bursa is well developed and the spicules are 1.3-1.7mm long, with a gubernaculum. In female the vulva situated on the posterior part of the body. The eggs measure 90-105µm by 50-55µm.

 

Life Cycle- Life cycle is direct, infection occurs through oral route or per oral route. The infective larva has a relatively long tail. The third stage larvae undergo change in the wall of the small intestine prior to the third moult. Within 26 days the third stage larvae reach to the colon. The forth stage larvae develop mainly in the lumen of caecum. The fourth moult occurs on an average of 24 days after infection. Immature parasite becomes adult and lay eggs in the colon after 49 days of infection.

 

Pathogenesis and Symptoms- The adult worms attach themselves firmly to the mucosa of the colon by means of their buccal capsule and suck blood accidently when a blood vessel is ruptured. The adjoining parts of the mucosa show an increased activity of Goblet cells and infiltration with Lymphocytes and Eosinophils. The symptoms are diarrhoea with much blood and mucosa. In severe infections animal loses condition and becomes anaemic and may die.  Chaebertina infections may be responsible for specific reduction of wool growth in sheep.

 

Diagnosis- By finding eggs in feces.

 

Treatment- Phenothiazine- 30g for calves and 60g for adult cattle single dose.

                     Piperazine compound- 200mg/kg b.wt. single dose.

 

 

 

 

 

 

 

Genus 6- Bourgelatia diducta

Location and Host- Parasites are found in the caecum and colon of pig in India, South East Asia and Java.

 

Morphology- Males are 9-12mm long and females are about 11-13.5mm long. The mouth is directed straight forwards. The buccal capsule is cylindrical and shallow and its thick wall is divided into an anterior and posterior portion. Buccal capsule is continuous with the lining of the wide oesophageal funnel. The external leaf crown has twenty-one long elements projecting from the oral aperture and the internal leaf crown has about twice as many elements. In male the spicules are equal in size. In female the vulva opens near the anus. The posterior end of the female is straight and ends in a sharp point. The eggs measure 58-77 by 36-42µm.

 

Life Cycle- The life cycle is direct and may be similar to the Chabertina species.

 

Pathogenesis and Symptoms - Pathogenicity and symptoms are not apparently marked.

 

Diagnosis- By finding the eggs in the fecal examination.

 

Treatment- Piperazine compound- 200mg/kg b.wt. single dose orally.

 

 

Family 3- Stephanuridae

 Genus 1 - Stephanurus

Species- dentatus (kidney worm of swine)

 

Location and Host- Parasites are mostly found in the peri-renal fat, pelvis of the kidney and wall of the ureter. But as an erratic parasite they are also found in liver or other abdominal organs and sometimes thoracic organs as well as in spinal cord of the pig. It is seen rarely in the liver of cattle but has also been reported from a donkey.

 

Morphology- Males are 20-30mm long, females 30-45mm long. The buccal capsule is cup shaped. At the base of the buccal capsule about six teeth are present. The anterior margin of the buccal capsule has leaf crowns and six external cuticular thickenings which is called as ‘Epaulates’. In case of male the bursa is small with soft rays and a pair of spicules. In case of females the vulva opens close to the anus.

Life Cycle- Eggs are passed out with the urine. The first stage larva hatch outside and moult into the 2^nd stage. The third stage larvae develop within 5-6 days. The third stage larvae may be ingested with contaminated food and water and that way they penetrate the wall of the stomach. Mostly animals are infected by percutaneous infection. In case of oral infection the larvae reach the kidney via the portal vessels in three days or longer. By the route of infection through skin penetration, the larvae reach into the kidney through the lungs by the systemic circulation in eight to forty days after infection. Parasites wander about below the liver capsule layer, later they penetrate into the peritoneal cavity and reach to the renal tube. After having reached the peri-renal tissues they perforate the walls of the ureter and produce a cyst which continues to communicate with the ureter through a fine canal. After percutaneous infection some parasites remain in the pulmonary capillaries and become encapsulated in the lungs or they may wander further and reach the pleural cavity and other thoracic parts. These larvae may also encapsulte in the liver. Some times they penetrate the placenta and prenatal infections have also been also reported. Some times Earthworm may act as paratenic host.

 

Pathogenesis and Symptoms- Migration of the larvae through the skin results in the formation of small nodules associated with enlargements of superficial lymph glands. During the migration of larvae to the liver it may result in the damage of liver tissues and cause cirrhosis of liver. The adult parasites may cause thickening of the wall of the ureter, resulting in blockage of the ureter. The common symptoms are subcutaneous nodule formation, paralysis of posterior part of the body, weakness, emaciation and reduction in the growth rate. Some times abdominal pain may occur in infected animals.

Diagnosis- By findings the eggs in urine examination.

 

Treatment- There is no satisfactory treatment for the parasite but Thiabendazole  50 mg / kg body weight  inhibits the migration of the larvae and adult parasite.

 

Family 4-Syngamidae

Genus - Syngamus

Species - S. trachea (Gape worm of fowl)

 

Location and Host- Adult parasites are found in the trachea of fowl, pigeon, Turkey, Guinea fowl, Goose and various related wild birds throughout the world.

 

Morphology- The male and female parasites remain attached with each other and they appear as they are always in copulation and both parasites remain in “Y” shape manner. The size of the male parasite is 2-6 mm long and female parasite is 5-20 mm long. The buccal capsule is cup shaped and the base of the buccal capsule consists of 6-12 small teeth. In case of male the bursa is very small with short and stout rays. The eggs appear similar to those of Strongylus eggs but they have a thickening near the operculum at either pole. Eggs measure about 70-100 by 43-46µm in diameter.

 

Life Cycle- The life cycle is usually completed in only one host. The eggs are usually coughed up and swallowed by the host and they are passed out with the feces. The larvae moult twice inside the eggs and the third stage infective larvae are found in the ninth day in the eggs. The third stage larvae, eggs or some time already hatched larvae infect the final host through contamination of food and water. The larvae penetrate the intestinal wall and via circulation reach into the lungs. In the lungs alveoli they moult in to the fourth stage larvae after which the sexes can be differentiated. The final moult occurs in the fourth or fifth day of infection and the worms migrate to the large bronchi where copulation takes place. Some times life cycle is also possible when the infective larvae are ingested by the earthworm, snail, slug, flies and other arthropods, in which they become en-cysted and later infect the final host when they are being ingested by them.

      

Pathogenesis and Symptoms- The adult parasites produces pin point hemorrhages in the wall of the trachea and lungs. There is inflammation of trachea with the production of large amount of mucous. The mucous blocks the respiratory passage causing difficulty in respiration. The symptoms are difficulty in breathing associated with whistling sound. Due to difficulty in breathing the bird shows gaping symptoms i.e. the bird shakes and tosses its head about and it may cough or it extends its neck, opens the beak and performs gaping movements. In heavy infection it results in death of the bird.

       

Diagnosis- By gaping symptoms of infected birds and finding the eggs in fecal examination.

 

Treatment- Thiabendazole ; 0.3- 1.5 gram / bird orally, successful to chicken and turkey.

                     Albendazole:- 7.5mg /kg. body weight orally.

                    Mebendazole and Fenbendazole:- 0.01 % mix in the feed and provide for 7-14 days.

 

 

Family 5- Ancylostomatidae

Subfamily- Ancylostominae

Genus 1– Ancylostoma

Species- A. caninum (Hook worm of dog and fox)

 

Location and Host- Adult parasites are found in the small intestine of dog, fox and rarely in human beings.

 

Morphology – Males parasite are 10-12mm long and females are about 14-16mm long. Anterior part of the parasite is bent dorsally and gives an appearance of hooks. The buccal capsule is very deep and appears more chitinised, because the ventral margin of buccal capsule contains two pair of teeth, out of which the first is small and the second pair is largest one. At the base of the buccal capsule, there is a pair of triangular dorsal teeth and pair of ventrolateral teeth. The eggs are similar to Strongylus eggs, which are oval, thin shelled and transparent with segmental embryo. The segmentation is 2-16 cell divisions.

 

A. tubaeforme (Hook worm of Cat): They are found in the small intestine of cat. The only morphological difference is that the teeth on the ventral margin are slightly larger.

 

A. braziliense: Adult parasites are found in the small intestine of dog, cat, fox and rarely in man. The morphological difference is that the ventral margin of buccal capsule consists of only two pairs of teeth and out of these one pair is larger and other small.

 

A. duodenale (Hookworm of Man): It is found in duodenum. Only difference is that the ventral margin of buccal capsule contains three pair of teeth but out of these the first two pair are larger and last (third) is smaller.

 

 

 

 

 

Subfamily – Necatorinae

Genus 2– Necator

Species- N. americanus

Location and Host – Adult parasites are mostly found in the small intestine of man and rarely found in the small intestine of dog and pig.

 

Morphology – The species of this genus have one pair of ventral cutting plates, and at the base of the buccal capsule, one pair of ventral teeth and one pair of subdorsal teeth. The termination of the dorsal gutter projects into the buccal capsule as a prominence called as the dorsal cone.

 

Life Cycle – The eggs are passed out in the feces. They hatch in the pasture and the 3^rd stage infective larvae develop within 5 to 7 days. The larvae mostly infect by skin penetration but sometime infection also occurs by ingestion of contaminated food and water. After infection the larvae enter into the blood circulation. Through blood circulation they reach the lungs and then migrate into the bronchiole, bronchi, trachea and reach the esophagus. They are then swallowed and ultimately reach the intestine and become adult in 4-5 weeks.

 

(A. caninum & N. americanus) Pathogenesis and Symptoms – The disease is known as Ancylostomiasis. Young animals are more susceptible. Migration of larvae to the skin causes irritation and dermatitis. Migration of the larvae in the lungs may result in pin point hemorrhages. The adult parasite may remain attached to the wall of intestine and suck blood. These parasites are voracious blood suckers and one parasite can remove 0.03-0.2ml blood per day. Blood losses commence from about the eight day of infection. There is reduction of RBC and haemoglobin. Initially the anaemia is normocytic and normochromic, but as the animal becomes iron-deficient, a microcytic hypchromic anaemia is seen. Other symptoms are oedema, ascites, weakness and emaciation. The growth rate is reduced. The hair coat becomes dry and rough and diarrhoea mixed with blood or mucus or both is seen.

 

Diagnosis – From clinical symptoms and by finding the eggs in the feces.

 

Treatment –Tetrachloroethylene- 0.2ml/kg b.wt. followed by saline laxative (seldom used).

Alcopar – 20mg/kg. b.wt.

Mebendazole - 40mg/kg.b.wt. or 200mg orally twice a day for 3-4days.

Thiabendazole – 25mg/kg. b.wt.

Albendazole – 7.5mg/kg b.wt.

 

 

Genus 3 - Bunostomum

Species – B. trigonocephalum (Adult parasite found in the small intestine of sheep and goat)

B. phlebotomum  (Adult parasite is found in small intestine of cattle)

 

 

Morphology – The buccal capsule is relatively large in size. Teeth are absent on the ventral margin. At the base of the buccal capsule there is a pair of subventral lancet present in case of B. trigonocephalum but in case of B phlebotomum 2pairs of subventral lancet are present. The teeth on the ventral margin have chitinious plates absent. Apart from these there is a large dorsal cone present in the buccal capsule of B. trigonocephalum and shorter dorsal cone is found in B. phlebotomum. In case of male a well developed bursa is present. The dorsal lobe of the bursa is asymmetrical. The spicules are spoon shaped.

 

Life Cycle – The development is direct. Infection of the host occurs through mouth or skin penetration. After skin penetration the larvae pass to the lungs, where the third stage larvae moult into the fourth stage larvae which have a buccal capsule. They reach in the intestine after eleven days and the first egg is passed in 30-56 days after infection.

Pathogenesis and Symptoms – The main pathogenesis is progressive anaemia with associated changes in the blood picture and oedema, which is seen especially in the intermendibular region as a ‘Bottle Jaw Condition’. Diarrhoea is not frequent and the feces may be dark in colour due to present of altered blood picture (Malena).

 

Diagnosis – By finding and identification of eggs in fecal examination or identification of larvae in fecal culture as well as partly diagnosed from the clinical signs such as anaemia.

 

Treatment – Thiabendazole – 75mg/kg b.wt. orally.

Fenbendazole – 5mg/kg b.wt. orally.

Albendazole – 7.5mg/kg b.wt. orally.

Ivermectin – 1ml/50kg b.wt. subcutaneouly.

 

 

 

Genus 4 – Gaigeria

Species- G. pachyscelis

Location and Host – Adult parasites are found in the duodenum of Cattle and Zebu, Buffalo, Sheep and Goat in India.

 

It is pathogenic in young animals; about 24 parasites may cause the death of infected animal because they are voracious blood sucker. Only morphological difference between Bunostomum and Gaigeria is that the dorsal cone is well developed in the species of Bunostomum and reaches the margin of the buccal capsule. But in case of Gaigeria species the dorsal cone is small in size.

 

Life Cycle – Life cycle is direct and similar to that of other hookworms. Infection is only through skin penetration; larvae reach the lungs via blood circulation and remain there for 13 days. Then they travel to the trachea, pharynx and are swallowed and reach the small intestine. The worm grows to an adult in about ten weeks from the time of infection.

 

Treatment – Phenothiazine – 300-400mg/kg b.wt. orally.

Trichlorophane – 110mg/kg b.wt. orally.

Albendazole- 7.5mg/kg b.wt. orally.

 

 

Superfamily- Trichostrongyloidea

Family 6 – Trichostrongylidae

Genus – Trichostrongylus

 

Species                     Location and Host

T. colubriformis	Found in the duodenum of sheep, goat, cattle, camel and antelopes. Males are 4.5-5.5mm long and females are 4.5-7mm long.
T. falculatus	Small intestine of sheep, goat and antelope. Male s are 4.5-5.6 mm long.
T. vitrinus	Small intestine of sheep, goat, deer and occasionally also found in rabbit, camel and man. Male: 4-7mm long and Female: 5-8mm long.
T. axei	Found in the abomasum of sheep, goat, cattle, deer and in the stomach of pig,  horse and man. Male: 2.5-6mm long.
T. capricola	Small intestine of sheep and goat. Male 3.5-5mm long;Female 3.5-8mm long.
T. probolurus	Found in the small intestine of sheep, goat, camel and man. The parasites are more than 3.5mm long.
T. longispicularis	Small intestine of sheep. Male: 3-8mm long, Female: 6mm long.

 

Genus 1-  T. colubriformis

 

Morphology- Small parasite, slender and reddish brown in colour. Males are 4-6mm long and females are 5-7mm long. Buccal capsule is absent and one notch is present towards the anterior part of the body. In case of male the bursa has long lateral lobes and small dorsal lobe. The spicules are short brown pigmented and are cleft near the teeth.

 

Life Cycle – Development is direct. The eggs are passed in the feces of the host and are similar to Strongylus eggs. After passing out from the body, the first stage larva is developed from the egg which is followed by the 2^nd stage larva. Thus the infective third stage larva is produced in four to six day under optimum conditions. Infection is by ingestion of infective larva on herbage. In case of T. colubriformis and T. axei, the parasitic third stage larvae are found in the abomasum or small intestine two to five days after infection, the fourth stage larvae occurs at about seven days after infection and the fifth stage larvae are found 15days after infection. The prepatent period is about 20 days.

 

Pathogenesis and Symptoms – These parasites penetrate the intestinal mucosa and cause damage of the epithelial cells, about 2000 parasites can produce serious disease. Other symptoms are constipation followed by diarrhea, the skin appears rough and dry. In case of sheep Trichostrongylus colubriformis produces dark colored Diarrhea and is called ‘Black scours’ and thus, these parasite is known as Black Scours Worm.

 

Diagnosis – This is confirmed by making fecal culture and identification of the infective larvae.  

 

Treatment – Mebendazole – 15mg/kg b.wt. orally.

                     Fenbendazole – 7.5mg/kg b.wt. orally.

                     Albendazole – 5mg/kg b.wt. orally.

 

 

 

 

 

 

 

 

 

Genus 2 – Haemonchus

Species –H. contortus (Stomach worm or wire worm of Ruminant)

 

Location and Host- Adult parasites are found in the Abomasum of sheep, goat, cattle and numerous of other ruminants in most parts of the world.

 

Morphology- Male parasites are about 10-20 mm long and females are 18-30mm long. Males are reddish brown in colour but females are with white uterus and the ovary spirally surrounds the red intestine giving it a barber’s pole like appearance. The anterior end contains spine-like cervical papillae and in the buccal capsule subventral lancet is present. In case of male the bursa has elongated lateral lobe and small asymmetrical dorsal lobe. The dorsal ray appears like and inverted ‘Y’. Spicules are brown in colour and provided with small bark at the tip. In case of female the vulva is covered with a vulval flap which may be very large in size and tongue shaped or small in size and knob like.

 

Life Cycle- The eggs are passed out in the feces. The first stage larvae hatch out in the pasture and then change into the second stage larvae. The third stage infective larvae crawl and reach on the leaf blades of grasses. Infection occurs after ingestion of grass having the infective larva. Ex-sheathing occurs in the rumen and parasitic larval stages migrate to the abomasum and penetrate the area between gastric epithelial cells from which they emerge as fourth stage larvae. The fourth stage larvae become adult in the abomasum. The prepatent period for H. contortus in sheep is an average of 15days and for H. placei in cattle is between 26- 28 days.

 

Pathogenesis and Symptoms – Disease caused by Haemonchus is called Haemonchosis. Parasites are voracious blood suckers and produce anaemia with reduction of RBC’s, percentage Hb, and the packed cell volume (PCV). Young animals are more susceptible. In heavy infection bottle jaw condition also occurs and animal becomes emaciated. In case of sheep the wool may often be formed in patches. Postmortem shows a large amount of fluid in the peritoneal and pleural cavity. Due to anemia the conjunctiva becomes pale yellow in colour. The liver becomes light brown in colour with fatty regeneration. The abdominal mucosa is greatly swollen with pin point haemorrhages.

 

Diagnosis – A high fecal egg count including identification of larvae in fecal culture should be sufficient to establish a diagnosis.

 

Treatment – Crufomate – 16-35mg/kg in cattle and 40-90mg /kg b.wt. orally in sheep.

                      Albendazole – 5mg/kg b.wt. orally. 

                     Ivermectin – 1ml/50kg b.wt. S/C

 

 

Genus 3- Ostertagia (Brown Stomach Worm)

 

O. ostertagi	Abomasum of cattle and sheep	Male: 6.5-7.5mm long; Female: 8.5-9.2mm long
O. circumcincta	Abomasum of sheep and goat	Male, 7.5mm long;                                Female,7.5-8.5mm long
O. trifurcate	Abomasum of sheep, goat and some time also found in cattle	Male,6.5-7mm long
O. lyrata	Abomasum of cattle

Morphology – Small and slender parasites. The cuticle at the anterior end may be slightly inflated and there are transverse striations at the anterior part of the body. Rest of the body cuticle contains 25-35 longitudinal ridges. In case of male the bursa has two lateral lobes and one small dorsal lobe. The spicules are pigmented brown in colour. The vulva of female may be covered by a small anterior flap.

 

Life Cycle – Life cycle is direct and same as Haemonchus sp.

 

Pathogenesis and Symptoms – Parasites form nodules on the wall of the abomasum and cause severe chronic diarrhea and in heavy infections death may occur. Each parasite sucks blood and causes reduction of Hb, RBC%, and Serum protein level.

 

 

Genus 4 - Cooperia

C. punctata	Small intestine of cattle	Male: 4.7-5.9mm; Female: 5.7-7.5mm.
C. pectinata	Small intestine of cattle	Male: 7mm; Female: 5.7-9mm
C. oncophora	Small intestine of sheep and cattle	Male: 5.5-9mm;  Female: 6-8mm.
C. surnabada	Small intestine of sheep and camel	Male: 6.8mm; Female: 7.9mm
C. curticei	Small intestine of sheep and goat	Male: 4.5-5.4mm; Female: 5.8-6.2mm.

 

C. curticei

 

Morphology- Parasites are small and cylindrical. Males are 4.5- 5.4mm long and females are 5.8-6.2mm long. The cuticle at the anterior end forms a cephalic swelling and rest of the body cuticle has 14-16 longitudinal ridges, which are transversely striated. In case of male the dorsal lobe of the bursa is very small in size.

 

Life Cycle- The life cycle is direct and similar to Trichostrongylus.

 

Pathogenesis and Symptoms – Parasites penetrate the intestinal mucosa and suck blood. In heavy infections it causes anemia.

 

Treatment – Similar to Trichostrongylus.

 

 

Genus 5– Nematodirus

Species – N. spathiger (Thread Neck Strongyle)

 

Location and Host – Adult parasites are found in the small intestine of sheep, goat and cattle.

 

Morphology – Male parasites are 10-15mm long and female parasites are 15-23 mm long. Anterior portion of the parasite is thinner than posterior part. The cuticle has 14-18 transverse ridges. In case of male, the bursa has an elongated lateral lobe and dorsal lobe is split into two portions. Each half is attached with one lateral lobe. The spicules are large and slender. At the tip both of the spicules are fused together. In case of female the tail is very short with terminate appendages. Eggs are similar to the Strongyle eggs.

 

Life Cycle and Treatment are similar to Haemonchus. Prepatent period is 15 days; the third stage larva is the infective larva of the parasite. The adult parasite lives only few weeks.

Pathogenesis and Symptoms- Parasites penetrate and form tunnels in the wall of the small intestine causing extensive destruction and acute inflammation of the small intestine and emaciation of the animal.

 

Control of Gastro-Intestinal Nematodirus spp. - Control method is difficult especially in Nepalese condition. Larvae of Gastrointestinal Nematodirus is mostly found in the pasture during early morning time and later evening hours. Therefore, the animal should allowed to graze the pasture after 8am or should be removed the pasture before 4pm. Infective pastures should fenced with barbed wire and healthy animal should not be allowed to graze in this pasture, and infected animal should not allow to graze in uninfected pasture. Feces are removed suddenly and exposed to sunlight or kept in a heap so that fermentation takes place which is destructive for the larvae and eggs. The pasture should be regularly drained and kept dry. For killing of the larvae in the pasture, ploughing of the pasture or burning of the pasture land is essential. Infected animal should be treated regularly. Rotational grazing is highly effective for controlling the parasite. In this case the pasture land is divided into four parts and animals are allowed to graze on a particular plot for 10-15 days and this process is repeated in a rotational manner. By this the process the infective larvae that develop will die when animals return back to the same plot. Another method in where sheep, goat and cattle graze together, it is better to allow the cattle first and then allow the sheep and goat to graze. The feed and water should be kept clean and free from contamination of parasites.

 

 

Genus 6 - Mecistocirrus

Species- M. digitatus

 

Location and Host- Abomasum of sheep, goat, cattle and rarely man.

 

Morphology- Males are 31mm long and females are 43mm long. In case of males bursa has a small symmetrical dorsal lobe with ‘Y’ shape dorsal rays. The spicules are slender and are united together in all their entire length.

 

Life Cycle- Life cycle is direct; the prepatent period is of 60days. In this parasite the 4^th larval stage lasts from 9-28days of infection.

 

Pathogenesis and Symptoms – This parasite is an important pathogen in endemic areas, the effect of infection is similar to Haemonchus species.

 

Diagnosis- By finding eggs in feces as well as fecal culture.

 

Treatment- Phenothiazine- 600-700mg/kg b.wt. orally, sheep and goat;(50-80gm/ large animal)

                    Thiabendazole – 50mg/kg b.wt.

                    Parabendazole- 50mg/kg b.wt.

                    Albendazole- 5mg/kg b.wt. orally.

                    Alcopar- 250mg  orally.

                    Ivermectin –1ml/50kg b.wt. s/c.

 

 

 

 

 

Superfamily - Trichostrongyloidea

Family –7 Ollulanidae

Genus – Ollulanus tricuspis

 

Location and Host- Parasites are found in the stomach of the cat, fox and pig in Europe, North America and Australia.

 

Morphology – Males are 0.7-0.8mm long and the females are 0.8-1mm long. A small buccal cavity is present. In male bursa is well developed and the spicules are long, stout and are split into two for a considerable distance. The tail of the female ends as three or more short cusps (tooth like structure). The vulva is situated in the posterior part of the body and there is only one uterus and ovary. The worms are ovoviviparous.

 

Life Cycle – The larvae develop in the uterus of the female parasite to the third stage. The infection is spread through the vomit of an infected animal, which is eaten by another susceptible host. In addition the life cycle may be completed endogenously and heavy infections may result.

 

Pathogenesis and Symptoms- The parasite is considered to be relatively harmless to cats, although the worm burrows into the gastric mucosa, causing slight damage and increased secretion of mucus. A chronic gastritis and emaciation in pig is recorded.

 

 

Family 8- Dictyocaulidae

Genus – Dictyocaulus filaria (Rudolphi, 1803)

D. viviparous (Found in the bronchi of cattle, deer, buffalo and camel)

D. arnfieldi (Found in the bronchi of horse, donkey and zebra)

 

Location and Host – Parasites mostly found in the bronchi of sheep, goat and some wild ruminants, they have been recovered from Eastern Europe and India.

 

Morphology – The males are 3-8cm long and females are 5-10cm long. The worms are milky white in colour. There are four very small lips and a very small, shallow buccal capsule is present. In male bursa, the medio and posterolateral rays are fused together except at their tips, the externo-dorsal rays arise separately and the dorsal ray is cleft right from its base. The spicules are stout, dark-brown in colour. The vulva is situated just behind the middle of the body. The eggs measure 112-138 by 67-90µm in diameter and contain fully formed larvae when laid.

 

Life Cycle – The eggs may hatch in the lungs but are usually coughed up and swallowed, and first stage larva hatch while they pass through the alimentary tract of the host. Some eggs may be expelled in the nasal discharge or sputum. The first stage larva passes out in the feces which are easily recognized by the presence of a small cuticular knob at their anterior extremity. After one or two days the larva reaches the second stage. The third stage larva infects the final host through oral route. Larva penetrates the intestinal wall and within three days passes via the lymph vessels to the mesenteric lymph glands, where the third moult occurs about four days after infection. In the fourth stage males and females can be distinguished. The worms now pass via the lymph and blood vessels to the lungs where they break air sacs and reach in the bronchi where they become adult in about four weeks.

Pathogenesis and Symptoms- The worms live in the small bronchi, producing a catarrhal parasitic bronchitis and the inflammation also spreads to the surrounding peribronchial tissues and produces exudate frequently causing Atelectasis (incomplete expansion of lung) and pneumonia. Sometimes secondary bacterial infection may also occur. Others symptoms are cough and Dyspnoea.

 

Diagnosis – By finding the first stage larvae in the feces or eggs may be found in the sputum or nasal discharge.

 

Treatment – Tetramisole- 15mg/kg b.wt. orally.

Albendazole- 7.5mg/kg b.wt. orally.

Fendazole- 5mg/kg b.wt. orally.

Oxfendazole – 4.5mg/kg b.wt. orally

 

Superfamily – Metastrongyloidea

Family 9 – Metastrongylidae (Leiper, 1908)

Genus - Metastrongylus elongatus (syn. M. apri)

 

Location and Host – Parasites are mostly found in the bronchi and bronchioles of pig and wild pigs but have also been reported from the cattle, sheep, deer and in man. It is cosmopolitan in distribution.

 

Morphology –The male parasite measures about 25mm long and the female is about 58mm long. The worms are white and have six small lips or papillae around the oral aperture. In male the bursa is relatively small, the anterolateral ray is large and has a swollen tip, the mediolateral and posterolateral rays are fused and the dorsal rays are much reduced. The spicules are long and filiform in shape. The vulva opens near the anus. The eggs are 45-57 by 38-41µm in diameter and have thick, rough shell and contain a fully developed embryo when laid.

 

Life Cycle – The eggs are passed in the feces of the host and may hatch only after they have been swallowed by the intermediate hosts that are the different species of earthworm. The pigs becomes infected by ingestion the infected earthworms or accidentally liberated infective larvae. Other animals are infected by ingestion of accidentally liberated infected larvae. The infected larvae after ingestion reach to the intestine and penetrate the intestinal wall. They reach the mesenteric lymph glands via the lymph vessels. In the lymph glands the third moult occurs. Then parasites can be distinguished into males and females. Later these larvae pass into the walls of air sacs of lungs via blood and lymph vessels. After they break out of the wall of air sacs, they reach into the bronchi where they become adults. The first egg is laid after about 24 days of infection.

 

Pathogenesis and Symptoms – This parasite causes bronchitis, pneumonia, loss of condition and retardation of growth and sometimes secondary bacterial infection also occurs.

 

Diagnosis – By finding the embryonated eggs in the fresh feces.

 

Treatment – Tetramisole – 15mg/kg b.wt. orally.

Fenbandazole- 20-30mg/kg b.wt.

Alendazole-7.5mg/kg b.wt.

 

 

Superfamily – Metastrongyloidea

Family 10- Protostrongylidae (Leiper, 1926)

Genus – Protostrongylus rufescens (Leukart, 1865)

 

Location and Host- Parasites are found in the small bronchioles of sheep, goat and deer. Mostly found in Europe, Africa, Australia and North America.

 

Morphology – The males are 16-28mm long and the females are 25-35mm long. The worms are slender and reddish in colour. In male the bursa is short and straightened dorso-laterally by a chitinious plate on either side. The spicules are long tubular, with broad, membranous expansions. A gubernaculum is present. The vulva opens near the anus. The eggs are unsegmented when they are laid and measure 75-120 by 45-82µm in diameter.

 

Life Cycle- The eggs develop in the lungs of the host and the first stage larva is passed in the feces. The first stage larvae penetrate the foot of the snail. Different species of aquatic snails act as an intermediate host. The final host becomes infected by swallowing the infected snail with its food and the larvae passes to the lungs of the host via the mesentric lymphatic glands, in which the third moult takes place. The prepatent period has been recorded as 30-37 days. Transplacental transmission occurs and larvae have been found in the liver and lung of females and newborn lambs.

 

Pathogenesis and Symptoms – This parasite causes inflammation in the wall of bronchioles and exudate fills in the alveoli. Severe infections affect the general heath and may cause death. The weakened lungs are susceptible to bacterial invasion which may produce acute pneumonia.

 

Diagnosis – By finding the larvae in the feces as well as the symptoms of the disease.

 

Treatment – Albendazole-5mg/kg b.wt.

Levamisole-20mg/kgb.wt.

Fenbendazole- 20-80mg/kgb.wt.

 

 

Family 11- Filaroididae (Schutz, 1951)

Genus – Filaroidea osleri (Cobbold, 1879)

 

Location and Host- Parasites are found in the nodules in the trachea and bronchi and rarely in the lungs of the dog and wild dogs in India, USA and other part of the World.

 

Morphology – Males are 5mm long and females are 9-15mm long and the body is slender in shape. The hind end of the male is rounded and bears a few papillae. The spicules are short and slightly unequal. The vulva is close to the anus. Parasites are ovoviviparous.

 

Life Cycle – The life cycle direct. The eggs hatch inside the body of the definitive host. There is no need of intermediate host. The first stage larva is found in the saliva or feces and is immediately infective for the definite host. Infection is probably transmitted from a bitch to her pups when she is licking and cleaning them. Infection by fecal contamination is also possible. After ingestion larvae migrate via the lymphatics and venous portal systems to the heart and lungs where upon they migrate up the bronchi and also other appropriate sites. The prepatent period is about 10 weeks.

Pathogensis and Symptoms – The worms live in or under the mucosa of the trachea or bronchi and cause the development of granulomas. In severe infections hemorrhagic lesions are found in the bifurcation of the trachea. The most common symptoms are rasping, persistent cough, loss of appetite and emaciation. Mortality may reach 75% in infected cases.

 

Diagnosis – By the finding the larvae in the sputum or larvae may be found in feces.

 

Treatment – Thiabendazole: 64-140mg/kg/day divided into two doses a day and given for 23days.

                        Fenbendazole – 100mg/kg given twice at a three days interval

 

Subclas-. Secernentea, Dougherty, 1958 (formerly Phasmida) (Phasmid present, amphid pore like, labial in position. Male parasite commonly posses caudal alae or bursa)

Order- Ascaridida

Suborder-Ascaridata

Super family-Ascaroidea

Family 1- Ascarididae (Two spicules, development direct or indirect, teeth present but no buccal capsule or pharynx, oviparous, the tail of the male is coiled)

Genus- Ascaris

Species- A. suum (Found in the small intestine of pig)

A. lumbricoides  (Found in the small intestine of man)

Toxocara vitulorum (Roundworm of cattle)

Ascaridia galli (Roundworm of Fowl)

 

Previously it was thought that the two species of Ascaris were not separate. Recently it has been seen that the two are entirely different species due to serological and immunological differences and due to value of cross infection.

 

 

Genus 1- Ascaris suum

 

Location and host- Adult parasite is found in the small intestine of pig.

 

Morphology- The male parasite measures about 15-25cm long and 3-5mm wide and female is about 42cm long and 5mm wide. The cuticle is very thin and parasites are rigid and tough. Both the ends are pointed. At the anterior end the mouth opening has three lips, one dorsal and two are sub-ventral. The dorsal lip has two double papillae and sub ventral lip has one double and one single papilla. The posterior end of the male may be slightly coiled and has two well-developed spicules which are stout and measure about 2mm in length. There are a large number of pre-cloacal papillae and few posterior cloacal papillae are present. In case of female the uterus is opisthodelph type and vulva is situated at the anterior 1/3 part of the body.

Eggs: Eggs are oval in shape and measure about 57-75x 40-50µm which is very thick shelled and is surrounded by an albuminous layer which is seen as a prominent projection. Eggs of A. suum and egg of A. lumbricoides are similar.

 

Life cycle- A female parasite may lay as many as 2, 00,000 - 2, 50,000 eggs per day. The eggs are passed out in feces. In the external environment (soil) the infective larvae i.e., 2^nd stage develops inside the egg after 10 days or later. When infective eggs are ingested by a definitive host Rabditiform larvae hatch out in the small intestine. These larvae penetrate the intestinal wall and reach the liver, majority reach by the way of the hepato-portal blood stream but few reach by the way of the peritoneal cavity within 24 hours. Inside the liver the larvae moult into 3^rd stage larvae. These 3^rd stage larvae reach the lungs via heart. In the lungs they break out of the lung capillary and reach the alveoli and migrate through the bronchioles, bronchi, trachea and to the larynx and pharynx. When they are swallowed, the third stage larva arrives in the small intestine seven to eight days after infection. Mature parasites are developed within 50-55 day after infection.

 

Pathogenesis and symptoms- Disease produced by Ascaris parasite is called Ascariasis. Migration of larvae inside the liver causes destruction of liver tissue and haemorrhages.  Migration of larvae inside the lungs causes haemorrhages and heavy infection and there also may be death of the young animal. The adult parasite found in small intestine causes enteritis and if they are found in a large number they may block the intestinal lumen and disturb digestion. These parasites are very migratory in nature; they migrate from the intestine and may reach in the stomach or enter in the bile duct and block the bile duct. The parasite may even penetrate the stomach and intestinal wall and cause peritonitis and sometimes ascites can also occur. Young animals are more susceptible and symptoms depend upon the severity of infection. In some cases due to migration of the larvae in the lungs parasitic pneumonia is seen. The animal may cough frequently and their growth may be stunted in case of piglets.  

 

Diagnosis- By finding the eggs in fecal examination and also looking for the common symptoms of the disease.

 

Treatment

• Piperazine compound (drug of choice for all roundworms) - (Piperazine citrate, adipate and dihydrochloride etc.) 100-300mg/kg b.wt. This is 100% effective. The crystal form of the drug is provided with feed.
• Piperazine hexahydrate (Vermex) - 15ml or tab.spoon full, mixed with water and given per 30kg b.wt.
• Teramisole (Tetramisole hydrochloride) - 15mg/kg b.wt in the feed.
• Fenbendazole- 7.5mg/kg bd.wt.

 

Prophylaxis: Infected animal should be treated immediately. Screening test for sputum and cough should be done. Proper management of animal hygeine should be done.

 

 

Genus 2- Parascaris

P. equorum (Large Round Worm of Equines)

 

Location and host- Small intestine of horse, mules and zebra.

 

Morphology- The male parasite measures 15-28cm and female parasite is about 50cm long. The body cuticle is very tough and rigid. The parasite has a very stout and large head. The lips are three and large. Three lips surround the mouth opening and these lips are separated by three intermediate small lips. In case of male the tail has caudal alae and a large number of pre-cloacal papillae and a single median papila. Two pairs of double and three pairs of single posterior cloacal papilla are present. In case of female the vulva is situated at the anterior fourth of the body.

 

Eggs- Eggs are spherical or subglobular in shape. The shell is very thick and the albuminous layer is pitted in appearance. They measure about 90-100µm in diameter.

 

Life cycle is same as A. suum.

 

Treatment –Piperazine compound 100mg/kg b.wt.

 

Genus 3- Toxascaris

T. leonina (Arrowheaded worm of canine)

 

Location and host- Adult parasite is found in the small intestine of dog, cat and fox.

 

Morphology- Anterior part of the parasite is bent dorsally and is provided with cervical alae. In case of female the uterus is opisthodelph type.

 

Egg-Eggs are smooth but thick shelled, oval shaped and measuring about 75-85x 60-75µm.

 

Life cycle- Generally no migration occurs to lungs and liver and the parasite becomes adult in small intestine and all moults occur there. Sometimes prenatal infection also occurs.

 

Treatment- Same as A. suum.

 

 

Genus 4- Toxocara

Species- T. canis - Found in the small intestine of dog and fox.

T. cati- Found in the small intestine of cat.

 

Morphology- These parasites are also known as Arrow headed worms. In the anterior end a large cervical alae is present. The male measures about 10cm long and female is 18cm long. The uterus is of amphidelph type. In case of female caudal alae is present at the posterior end of the body. The eggs are sub-globular, with thick finely pitted shell and measure about 90 by 75µm.

 

Life cycle- T. canis has two phages of life cycle, migration of larva is two type-

1. Somatic type of migration- When the infective eggs containing the 2^nd stage larva is ingested by the definitive host, the larva hatch out in the small intestine, then penetrates the intestinal wall and through blood circulation reaches different parts of the body. In the somatic organs these larvae become encysted and remain in a dormant condition for some time. In case of female dog while she becomes pregnant, due to some hormonal action these larvae are activated and they become mobile and they enter into the blood circulation. Through the placental circulation they may reach to the foetus so, in this case prenatal infection also occur.
2. Neonatal infection of puppies from the nourishing bitch occurs through the transmammary route of infection. Larvae are passed to the suckling pups via milk colostrum and develop into the adult worm in the intestine of pups.
3. Tracheal route- When the foetus is born it harbors the parasite in the liver and these larvae moult into 3^rd stage larvae. Through the blood circulation they reach the lungs and through bronchioles, bronchi and trachea reach into the pharynx. Finally these larvae enter into the pharynx and are swallowed by the young pups. The larvae moult to 4^th and 5^th stages in the intestine and become adults.
4. Tidal infection- Direct infection is seen in case of Pups with Prenatal Infection.

Pathogenesis and Symptoms of Ascariasis in Dogs and Cats

Young animals are more susceptible and some time heavy prenatal infection with T.canis may result in the death of puppies. Migration of larvae in lungs causes pneumonia and migration of larvae in liver cause destruction of liver tissue and may cause toxaemia and death may occur. They may cause haemorrhagic enteritis, unthriftiness and dark liquid feces. Mature parasites block the intestinal lumen and opening of the bile duct resulting in jaundice and other digestive disturbances. Due to the toxic substances produced by these parasites nervous disturbance symptoms may be seen. The other symptoms are weakness, vomiting, diarrhoea, emaciation, anaemia and associated restlessness. The hair coat is dry and rough. Some time Ascaris parasite may come out from vomit.

 

Diagnosis- From clinical symptoms or by finding the eggs in feces. Eggs are similar to Parascaris equorum.

 

Treatment – Piperazine –100mg/kg b.wt. for killing adult parasite.

                                          200mg/kg b.wt. for killing larval stages.

                     Diethylcarbamazine –50mg/kg b.wt. for cat and dogs

                     Fenbendazole  -  100mg/kg b.wt. single dose.

                     Mebendazole – 10mg/kg single dose

 

Zoonotic importance of the parasite- In case on children the larvae of T. canis, T. cati, Toxascaris leonina and Capillaria hepatica produce a disease condition called as Visceral Larvae Migrans. The children have special habit of eating soil and the infective eggs of these parasites are generally present in the soil in large doses. Due to this there is a Granulomatous Eosinophilia and lesions in various tissues such as lungs, liver, brain and eye. The important symptoms are loss of body weight, loss of appetite, cough, and fever. This can be diagnosed by taking biopsy material of liver. If the larvae are present in eye it may cause blindness of the eye.

 

 

Genus 5– Toxocara

Species –vitulorum (syn. Neoascaris vitulorum)

 

Location and Host- Adult parasite is found in the small intestine of cattle and buffalo some time also recorded from the sheep and goat.

 

Morphology- Adult male parasite measures about 25cm long and 5mm wide and female is about 35cm long and 6mm wide. The cuticle is soft and transparent. Mouth opening has three lips and these lips are broader at the base and narrow at the tip. The anterior end of head is narrow. In case of male posterior end has 5 pair of posterior cloacal papillae out of these 5pair, the anterior pair is broad and double. In case of female the vulva is situated near the 2/8^th of the body. Uterus is opisthodelph type. Eggs are subglobular, provided with a finely pitted albuminous layer and measure 75-95 by 60-75µm.

 

Life Cycle- Adult stage of T. vitulorum is mostly found in calves and prenatal and transmammary infections are the major sources of parasites for calves. The life cycle of T. vitulorum resembles with that of T. canis.

 

Pathogenesis and Symptoms- Migration of larvae through lungs cause hemorrhage, pneumonia and other symptoms like clay coloured diarrhea. They block the intestine and cause digestive disturbances. In heavy infection the young calves show emaciation and it is associated with colic pain and death also may occur.

 

Diagnosis- Disease is diagnosed from the symptoms and by finding the eggs in feces.

 

Treatment- Piprazine compound –200mg/kg b.wt. single dose

                   Piperazine hexahydrate (vormex)-1-2 tab. spoonful.

                   Fenbendazole- 5mg/kg bowt. single dose   

 

 

Family 2- Anisakidae

 

Members of this family possess one or more of the following features at the base of the Oesophagus:

1. Oesophagus with cylindrical ventriculus but intestinal caecum is absent e.g. Anisakis

2. Posterior ventriculus and anterior caecum projecting forward along the oesophagus e.g., Porrocaecum.

3. Posterior ventriculus, anterior caecum and posterior appendix projecting backwards from from the vetriculus e.g. Contracaecum

 

 

Genus 1- Porrocaecum  Raillet and Honry, 1912.

Species- P. crassum

 

Location and host- Parasite is mostly found in the intestine of domestic and wild ducks.

 

Morphology- Male parasite is about 12-30mm long and the female is 40-55mm long. The worms are reddish-white in colour. A short anterior caecum arises from the gut. The tail of the male is conical and there are no caudal alae. The eggs are oval, reticulate (a network appearance) and measure 65by 110µm.

 

Life Cycle- Life cycle is completed in two hosts. The intermediate hosts are earthworms of the genera Lumbricus and Octolasium. The intermediate host is infected after swallowing the eggs of parasites with the soil. Inside the intermediate host eggs hatch out. The final host is infected when it ingests the infected earthworm. Inside the duodenum of the final host, 2^nd stage larvae are formed and they moult into the 3^rd stage. Later they develop into the adult parasite.

 

Pathogenesis and Symptoms- The parasite causes reduction of body weight, diarrhoea, anorexia etc. A foamy mucus discharge from the nose and anaemia also occurs.

Treatment- Piperazine-133-300mg/kg b.wt. single dose.

 

 

Genus 2- Anisakis (The Herring Worm)

 

Location and Host- Parasite of this genus is mostly found in the intestine of marine mammals, birds, fish and accidentally man is also infected from the parasite.

 

Morphology- Body of the parasite is long cylindrical, the anterior region of the lips forms medial, bilobed processes. An intestinal caecum is absent.

 

Life Cycle- Life cycle of this parasite is completed in two hosts. The intermediate hosts are marine fishes but some species of fresh water fishes acts as an intermediate host. Humans are infected after ingestion of raw or semi-raw fish, which contains such larval stages.

 

Pathogenesis and Symptoms- In humans the pathogenesis caused by this parasite is called Anisakiasis or Herring Worm Disease. The common symptoms of this disease are irritation of the bowel with an Eosinophilic Granuloma in the intestinal or sometimes stomach wall.

 

Treatment- Piperazine salt- 3 to 4g single dose for adult and 2 to 3g single dose for under six      years aged animal.

                    Tetramisole- 2.5mg/kg b.wt. orally single dose.

                    Thiabendazole- 25mg/kg b.wt. twice a day for 2 days given after evening   

                    meal in tube.

 

 

Superfamily- Oxyuroidea

Family 3- Oxyuridae

Genus- Oxyuris

Species- O. equi (pin worm of horse)

 

Fig. Oxyuris equi

 

Location and Host- Adult parasite is found in the caecum and colon of horse, donkey and mule.

 

Morphology- Males are very small measuring about 9-12mm long and females are upto 150mm long. The mouth opening is hexagonal and contains some buccal teeth. The oesophagous is narrow at the middle and broad posteriorly. Posterior bulb like structure of oesophagus is absent. In case of male only one pin shaped spicule and two pairs of large papillae and few small papillae are also present around the cloacal opening. The immature females are white, but mature females are slightly gray in colour. Its tail is pointed and is three times larger than the body. The eggs are oval in shape and one side of the egg is slightly flattened and provided with a transparent plug at one pole. They measure about 90 by 42µm.

 

Life Cycle- Female parasites are found in caecum and colon and after fertilization females migrate to the anal region and deposit eggs in cluster in the skin of the perineal region. Inside the eggs the infective larvae develop within 3-4 days. These eggs fall down in the ground or may be ingested by horses with contaminated water or food. The eggs may also be attached to the perineal region, while licking of the perineal region the eggs may be taken and auto infection occurs. The larvae are liberated in the small intestine and reach the caecum and colon and become mature within 4-5 months after three moults.

 

Pathogenesis and Symptoms- When the female parasite migrates towards the anus, they lay eggs causing irritation at the anal region. Due to this the horse rubs the tail against hard object causing loss of hairs and damage of the tail. Due to constant irritation the animals becomes restless and loss of condition occurs. The adult parasite may cause digestive disturbances.

 

Diagnosis- Disease is diagnosed from the clinical symptoms. Presence of creamy coloured masses of eggs around the perineal region is indicative of the disease. When fecal sample is examined the eggs may not be found because these eggs are found in the perineal region. A NIH swab may be taken for examination and diagnosis of the parasite.

 

Treatment- Piperazin compound 400mg/kg b.wt. single dose orally.

                    Thiabendazole- 100mg/kg b.wt. single dose orally.

                    Mebendazole- 5-10mg/kg b.wt. single dose orally.

                    Cambendazole- 26-52mg/kg b.wt. single dose orally.

 

 

Super family- Subuluroidea

Family 4- Heterakidae

Genus 1- Ascaridia

Species- A. galli (large round worm of fowl)

 

Location and Host- Adult parasite is found in the small intestine of chicken, guinea fowl, turkeys and goose and other wild birds.

 

Morphology- Males measure about 50-76mm long and females are 72-116mm long. Mouth opening has three lips. Oesophageal posterior bulb is absent and club shaped appearance also is absent. In case of male the tail has caudal alae, which is small in size.  The tail bears ten pairs of papillae and a circular precloacal sucker. The spicules are equal in size. In case of female the vulva is situated anterior to the middle of the body. The eggs are oval in shape. They are with smooth shell and with unsegmented embryonic mass. They measure about 73-92 by 45-57µm.

 

Life Cycle- Eggs are passed out in the feces. The 2^nd stage larvae develop inside the egg within ten days. Eggs are ingested by host with contaminated food and water. Eggs reach the small intestine and larvae remain for eight days in small intestine and then they penetrate the intestinal wall and remain in the small intestinal wall for 10-17 days. Then they return back to the lumen of small intestine and become adult within 6-8 weeks.

 

Pathogenesis and Symptoms- Young animals are more susceptible. Predisposing factors are Vit. A, B and B₁₂ deficiency. Deficiency of other minerals and protein also act as a predisposing factor in heavy infection. Migration of larvae in walls of the intestine results in hemorrhages, enteritis and formation of ulcer, diarrhea, anemia, emaciation, weakness and egg production is reduced in poultry. Heavy infection may obstruct the intestinal lumen.

 

Diagnosis- By finding eggs of the parasite in the feces and by finding the adult parasite and also by findings from the post mortem report.

 

Treatment- Piperazine- 300-400mg/kg b.wt. mixed in feed.

                   Pnenothiazine- 200mg/kg b.wt.

 

Prophylaxis- Ascaris infection of poultry bird is major disease factor which reduces the egg production. Hence the treatment of the laying bird should be done once in a month. Other types of prophylaxis are to supply major and minor minerals, protein and vitamins adequately in the feed. Young birds should be kept separately.

 

 

Genus 2- Heterakis

Species- H. gallinarum (syn. H. gallinae, H. papillosa, H. vesicularis)

 

Location and Host- Adult parasite is found in the caecum of fowl, guinea fowl, pea fowl, turkey, goose and other birds.

 

Morphology- Males are about 7-13 mm long and females are about 10-15mm in length. Large lateral alae are present extending a long distance from the anterior part of the body. The oesophagus has a strong posterior bulb. The tail of the male is divided into large caudal alae. A prominent circular preclocal sucker and twelve pairs of papillae are present. The spicules are unequal in size. The right spicule is slender and about 2mm in length. The left one is broad and provided with an alae. In case of female the vulva is situated just behind the middle of the body. The eggs are similar to the Oxyuris equi having thick shell but smaller in size.

 

Life Cycle- Eggs are passed out through the feces. The 2^nd infective larva develops within 14 days. Definitive host is infected when the infective eggs are ingested with contaminated food and water. Infected eggs hatch in small intestine and they moult into 3^rd stage larvae in six days. They become the 4^th stage larvae in ten days and the 5^th stage larvae in fifteen days. Adult parasites are found 20-30 days of infection in the caecum.

 

Pathogenesis and Symptoms- Thickening of caecal mucosa, associated with pin point haemorrhages is seen. They produce marked lesions on the caecal wall. Diarrhoea, emaciation and death may also occur. Apart from this the eggs act as a carrier of a protozoan disease called as Black Head (Enterohepatitis) caused by Histomonas meleagridis which is normally lethal to the Blackhead organisms mostly found in the case of turkeys.

 

Diagnosis- By finding the eggs of parasite on fecal examination.

 

Treatment- Piperazine- 300-400mg/kg bowt. single dose.

                   Phenothiazine- 1gm/bird single dose orally is highly effective.

Other species are Heterakis brevispeculum found in fowl, H. dispar in fowl, H. isolanche found in fowl and pigeon.

 

 

Family 5- Subuluridae

Genus- Subulura brumpti

 

Location and Host- Parasites mostly occur in the caecum of the fowl, turkey, guinea fowl and wild related birds in Africa, Asia and North and South America.

 

Morphology- Males are 6.8-10mm long and the females are 9-17.5mm long. Lateral alae are present. The small buccal capsule has three teeth at its base. The esophagus has a small swelling at posterior, followed by a deep constriction and then a spherical bulb. The tail of male is provided with large lateral alae. The pre-cloacal sucker is an elongated slit, surrounded by radiating muscle fibres. There are ten pairs of small caudal papillae. The spicules are one pair and are equal in size. The vulva is situated just anterior to the middle of the body. The eggs are subglobular with smooth shell and contain a fully developed embryo when laid. They measure 52-64 by 41-49µm.

 

Life cycle- The intermediate hosts are various beetles of the genera Blaps and Gonocephalum and the cockroach Blatella germanica.

 

Pathogenesis and Symptoms- Pathogenicity and symptoms are not apparently marked.

 

Diagnosis- By finding eggs of the parasite in the fecal examination.

 

Treatment- Piperazine- 300-400mg/kg b.wt, orally single dose.

                    Mebendazole – 2g given in 28kg of feed.

 

Order – Spirurida (Chitwood, 1933)

Superfamily - Spiruroidea

Order – Spirudida

Family 1- Spiruridae

Genus 1 – Habronema (Stomach Worm of Horses)

Species- H. muscae

 

Location and Host – Adult parasites are found in the stomach of horses.

 

Morphology – Males are 7-14mm long and females are 13-22mm long. Buccal capsule is cylindrical and has a thick cuticular lining. There are lateral lips and each lip is in trilobes. In case of male a broad caudal alae are present. The spicules are unequal in size. The left spicule is five times larger than the right. The parasites are transmitted by Musca domestica, which act as intermediate hosts.

Genus 2- H. microstoma

 

Location and Host- Parasites are found in the stomach of horses.

 

Morphology – Buccal capsule is cylindrical and contains dorsal and ventral lips. The left spicule is two times larger than the right spicule. These parasites are viviparous in nature. The parasites are transmitted by Stomoxys calcitrans (Stable fly)

 

Genus 3- H. megastoma

 

Location and Host- Parasites are present inside the wall of the stomach of horse.

 

Morphology- The head portion is marked off from the rest of the body. Buccal capsule is funnel shaped. The tail of the male is spirally coiled. These parasites are transmitted by Musca domestica. The worms are ovoviviparous.

 

Life Cycle- The embryonated eggs may hatch in the stomach or intestine. The larvae are passed out in the feces and taken by Maggots of the fly. Inside the Maggots they moult to the 2^nd stage larva. Inside the pupa of the fly the 3^rd stage infective larva is produced. And when the flies become adult the 3^rd stage infective larva is found in the body cavity of Musca domestica. From there the larva migrates forward and reaches the proboscis of the fly. When the fly feeds on the definitive host the larva is deposited on the lips, nostrils and open wounds of the definitive host. This can result to:

1. The Host may get infected by the fly incidentally when these flies suck blood as the food material.

2. The larvae are deposited in the nostrils, lips and wound of the horse when the fly feeds. Later the horse is infected by licking the nostril, lips and wounds.

 

Pathogenesis and Symptoms- Adult parasites produce tumors in the wall of the stomach and also penetrate the stomach wall and produce gastritis with the formation of more mucus and this condition is known as Gastric Habronemiasis. The larvae which are deposited on the wounds or the broken skin penetrate into the wound and the wound becomes more severe and these larvae can survive inside this wound for several months. This condition is known as Cutaneous Habronemiasis or Bursati or Granular Dermatitis or Summer Sores. This disease mostly occurs during summer season and automatically disappears during winter season.

 

Symptoms of Gastric Habronemiasis: No symptoms are seen except some digestive disorders. Bursati on the other hand mostly occurs in scrotum, inner side of eyes etc. There is a tendency of the wound to decrease in size the healing process in winter season. There is formation of granulation tissue in affected wounds.

 

Diagnosis – Gastric Habronemiasis is difficult to diagnose but it can be done by collecting the larvae through stomach fluid. For this purpose eight to ten liters of 2% solution of sodium bicarbonate at body temperature is introduced into the stomach by means of stomach tube and after 15-30minutes the fluid is draw back and examined for the presence of larvae. Cutaneous Habronemiasis can be diagnosed by examining the wound and finding the larvae inside the wound.

 

Treatment- For Gastric Habronemiasis

                                 Carbon bisulphide- 5ml/100kg b.wt. orally.

                                 Fenbendazole –15-60mg/kg b.wt. single dose orally.

         For Cutaneous Habronemiasis

                 Wound is cleaned with Ethylchloride.

                Wound is treated with 10% of Hydro-chloric acid solution two to three times a day.

Dusting powder over the wound, which contains Plaster of Paris 100parts, alum-20parts, quinine 10parts and Naphthalene 10parts, is also effective.

 

Family 2 –Acuariidae

Genus –Cheilospirura   (syn. Acuaria)

C. hamulosa (syn. Acuaria hamulosa)

 

Geographical Distribution- World wide in distribution especially in Asia, America and Europe.

 

Location and Host- Adult parasite is mostly found in the gizzard of the fowl and turkey.

 

Morphology- Parasites are elongated and the cuticular sides have grooves or epaulette-like thickenings. The size of adult males is 10-14mm long and females are 16-29mm long. The cordons are double cuticular ridges with an irregular outline and extend far back along the body. Lips are small and triangular in shape. The male has four pairs of pre-cloacal and six pairs of post cloacal papillae. The left spicule is slender and about seven times larger than right spicule, the right spicule is flattened. The vulva is situated just behind the middle. The egg measures 40-45by 24-27µm. and are embryonated when passed in the feces.

 

Life Cycle – The eggs pass out in the feces of the infected host and hatch after they are swallowed by the intermediate host. Intermediate hosts are grasshopper (Melanoplus, Oxyanitidula etc) various beetles and weevils. In these hosts infective stage of larva develops in three weeks and the final host is infected by ingestion of such intermediate hosts. The prepatent period is three weeks.

 

Pathogenesis and Symptoms- The parasites live underneath the horny lining of the gizzard, producing soft nodules in the musculature and thus weakening it. Severe infection produces emaciation, droopiness, weakness and anaemia.

 

Diagnosis- In mild infections the worms are noticed post-mortem only if the horny lining of the gizzard is removed. They are found in soft, yellowish red nodules, which are most frequently seen in the thinner parts of the wall. Several species of Cheilospirura may occur in fowls and turkeys and their eggs are difficult to distinguish from one another.

 

Treatment- No satisfactory remedy is known but Carbontetrachoride, Tetrachoroethylene (0.3mg/kg b.wt. orally single dose) and Iodophene (0.02mg/kg for 3-4days) is highly effective against both adult and immatures. Oil of chenopodium has been recommended in the past. However anthelmintics like Dichlorvos, Levamisole, Thiabendazole and Benzimidazole should be tried.

 

Prophylaxis- It is difficult in case of birds that run free. Since they cannot be prevented from eating the intermediate host, eating of beetles and weevils with the food must be prevented.

 

Family 3- Thelaziidae

Genus 1 – Thelazia (eye worms)

Species- T. rhodesii

T. lacrymalis

T. callipaeda

 

Geographical Distribution – Cosmopolitan in distribution.

 

Location and Host – Adult parasites are found in the conjunctiva of cattle but also found in goat, sheep and buffalo.

 

Morphology – Male parasites are 8-12mm long and females are 12-18mm long. These are milky white in colour. Cuticle has prominent transverse striations. In case of male 14 pairs of precloacal and 3 pairs of post cloacal papillae are present. The spicules are long.

 

Life Cycle – Life cycle is indirect and Musca fly (M. larvipara, M. amica, M. oseris) act as intermediate hosts. They deposit larvae on the eye secretions and it is taken from one animal to other when the Musca fly sits on the eye or eye secretion, because the larvae are ingested by Musca fly. Inside the Musca fly they penetrate the intestinal wall and reach the ovary and moult into 3^rd stage infective larvae. Then the larvae migrate anteriorly and come to the mouth part of the fly. Ultimately larvae are deposited in the conjunctiva of the animal.

 

Pathogenesis and Symptoms – Adult parasites are found behind and in the nictitating membrane, lacrimal and nasolacrimal duct and on the surface of conjunctiva. The main symptoms are:

1. The eye lids are swollen and covered with exudates and pus.
2. Excessive irritation of the eye.
3. Conjunctiva becomes red and congested.
4. May be progressive keratitis (inflammation or cornea) and there is ulceration of the cornea.

 

Diagnosis- In animals where excessive larvae are found if the conjunctiva is examined, a milky white parasite may be seen in the conjunctival sac. The first stage larvae may be found in the eye secretion.

 

Treatment- Remove parasite with the help of forceps and Methylridine 20ml subcutaneously.

Tetramisole- 15mg/kg b.wt. orally.

Levamisole- 5mg/kg b.wt. orally or 2ml of levamisole injected in the subconjunctival sac is more effective than orally given. 

 

Genus 2- Spirocerca

Species- S. lupi (Oesophageal Worm of Dogs)

 

Location and Host – Adult parasites are found in the wall of the oesophagous, stomach and aorta, and also some time found freely in stomach of dog and horse.

Morphology- Males are 30-54mm long and females 54-80mm long. Parasites are spirally coiled and they are pink in colour. Lips surround the mouth opening and are trilobed. Pharynx is short and small. In case of male the tail has a small lateral alae and a group of small papillae near the tip of the tail. Eggs are small in size, measure 30-37 by 11-15µm in diameter. Eggs are like gelatin capsules. They are thick shelled and contain a well developed larva when they are passed out in feces.

 

Life Cycle – Eggs are passed out in feces and ingested by intermediate host (coprophagus beetles) and hatch inside them. The third stage infective larvae are usually formed inside the tracheal tube of beetle. The definitive host is infected by ingesting the beetle and larvae reach in the stomach. The larvae migrate to the stomach wall. Through blood circulation they reach the aorta and from the aorta migrate to the oesophagus and become adult or some time if infected beetle is ingested by unusual host like hedgehogs, mice, rabbit and bird, the parasite becomes encysted on the wall of stomach. When these paratenic infected host is ingested by the final host then they are infected.

 

Pathogenesis and Symptoms – The migrating larvae produce hemorrhages, inflammatory reactions and necrosis, as well as purulent streaks or abscesses in the tissues in which they penetrate. The adult parasite forms nodules on the wall of oesophagous, stomach and some time aorta which contains cavities that harbor one or more of these worms. The lesions and scarring of the thoracic aorta are pathognomonic for infection with S. lupi. The intima is rough and granular and eosinophilic granulomatous reactions form nodules around parasitic cavitations in the media. There is degeneration of elastic tissue and replacement by collagen and eventual calcification and ossification of muscle. All this results in the stenosis of the aorta or formation of aneurysm with possible rupture of the vessel. In severe infections the nodular mass in the esophageal wall may become large and pedunculated and protrude in the lumen of the esophagus. This thus leads to interference with digestion. Other symptoms are vomiting, rapid loss of condition; parasite may be passed out through the feces or vomit.

 

Diagnosis- By findings the eggs on the feces or vomit or by clinical symptoms.

 

Treatment – Diethyl carbamazine, 20mg/kg b.wt. 4-8days.

Disophenol-1ml/5kg b.wt. s/c

Albendazole –7.5mg/kg b.wt. single dose.

Levamisole – 5mg/kg b.wt. orally single dose.

 

Family 4- Tetrameridae

Genus-Tetrameres

Species- mohtedai

 

Location and Host – Parasites are found in the proventriculus of fowl, they are reported from India and South East Asia.

 

Morphology- Male parasite is longer than female so there is sexual dimorphism. Female is spherical and red in colour, male is elongated and filliform.

 

Life Cycle – Lifecycle is completed in two hosts. The intermediate hosts are cockroach, grasshopper and moth. Parasite becomes adult after 35 days after infection in fowl.

 

Pathogenesis and Symptoms- The parasite causes thickening of the wall of proventriculus, excessive granuloma, necrosis of the tissue of proventriculus, anaemia and emaciation.

 

Diagnosis – By postmortem examination of the bird and finding eggs in fecal examination.

 

Treatment – Thiabendazole- 300mg/bird

Piperazine- 300-400mg/kg b.wt. orally.

 

Superfamily- Physalopteroidea (Sobolev 1949)

Family 5- Gnathostomatidae

Genus- Gnathostoma

Species- G. spinigerum (Thorney Headed Worm)

 

Location and Host- Adult parasites are mostly found in the stomach of dogs and cats but are also found in wild carnivorous animals.

 

Morphology – Males are 10-25mm long, females are 9-31mm long. At the anterior part of the body a head ball is present which contains four cuticular submedian cavities. The head bulb has 6-12 transverse rows of hooks. Anterior portion of the body consists of large cuticular spines. Eggs are oval in shape and a thin cap at one end of the egg is present. Egg shell is green in colour and are passed in one-cell or morula stage and measure about 69 by 37µm.

Life Cycle- It consist two intermediate host; Cyclops and Fresh water fish. Eggs are passed out in the feces and come in contact with water and hatch in four days time. When larvae are ingested by Cyclops they moult into the 3^rd stage infective larvae within 7 days. When the infected Cyclops is eaten by fresh water fish the 3^rd stage larvae encyst in the tissue of fresh water fish. The definitive host is infected by the ingestion of raw or improperly cooked fish. The parasite is liberated in the stomach and becomes adult within six months.

 

Pathogenesis and Symptoms- Adult parasite penetrate the wall of stomach and produce small cavities, which are filled with sanguinopurulent fluid. These cavities later on develop to thick walled cysts each containing upto nine worms. Sometimes larvae migrate into the liver and damage the liver tissue. Gastric tumor is also observed in infected cat. The symptoms are abdominal pain and diarrhoea. Sometime the larvae are present in peritoneal cavity and cause peritonitis.

Diagnosis- There is difficulty in the diagnosis of the disease because the eggs are rarely found in the feces.

 

Treatment- No satisfactory treatmen is available.

Albendazole-7.5mg/kg b.wt. orally can be used.

 

 

Suborder-Filariata

Superfamily- Filaroidea (Weinland, 1858)

Family 6- Filariidae (Claus,1856)

Genus- Dirofilaria

Species- D. immitis (Leidy, 1856)

Location and Host- Parasites are found in the right ventricle and the pulmonary artery and other part of the body of dog, cat, fox and wolf in the tropics, subtropics and some temperate regions.

 

Morphology-Males are 12-16cm long and females are 25-30 cm long. The worms are slender and white in colour. The hind end of the male is spirally coiled and the tail bears small lateral alae. There are four to six, usually five pairs of ovoid papillae, of which one pair is postcloacal, two pairs are of finger shaped papillae near the tip of the tail. The left spicule is larger then the right spicule. The vulva is situated just behind the end of the oesophagous. Females are ovoviviparous and microfilriae may be found in the blood at all times.

 

Life Cycle- The intermediate hosts are mosquitoes. For the first 24 hours after a blood meal the microfilariae are found in the stomach of the insect, during the next 24 hours they migrate to the malpighian tubule, where they develop over the next 15-16days. The final infective stage is produce in the labium. Development takes about 15-17 days in temperate countries while in tropical areas it may be a short as eight to ten days. Infection of the dog occurs when the infected mosquito takes a blood meal. Circulating microfilariae may survive upto two years and transplacental transmission may occur with microfilariae being found in neonatal pups.

 

Pathogenesis and Symptoms- Many dogs may be infected with D. immitis but there maybe no any clinical signs of infection. In heavy infections it causes circulatory distress due to mechanical interference, they also interfere with the function of the heart valves. Sometimes congestive heart failure also occurs, liver enlargement, ascites, and occasionally peripheral oedema also occurs.

 

Diagnosis- Diagnosis is based on clinical signs and demonstration of microfilariae in the blood.

 

Treatment- Arsenical Thiacetarsamide –0.1ml/0.45kg b.wt. bds for two or three days I/V(adulticide) (potential nephrotoxin and heapatotoxin; so its treatment should be stopped if toxicity is seen).

Melarsoprol- 100mg/kg b.wt. against the adult parasite.

Levamisole- 10mg/kg b.wt. for 15-20days.

Dithiazanine iodide – 2mg/045 kg b.wt. od for seven days (To remove microfilariae; but should not be used if hepatorenal disease is present).

 

Family 7- Setariidae

Genus- Setaria

Species- S. equina (Found in peritoneal cavity of equines)

S. labiata or S. papillosa (Found in cattle, deer, giraffe and antelopes)

S. digitata (Found in goat, sheep, cattle, buffalo and zebra in Asia)

S. cervi (Found in deer, and buffalo in India)

Genus 1- Setaria cervi

 

Location and Host- Parasites mostly occur in the peritoneal cavity of deer, and are also found in buffalo, cattle and zebu in Far East Asia.

 

Morphology- Males are 40-60mm long and females are 100-160mm long. Parasites are milky white in colour. The tail of the male bears four pairs of precloacal and usually four pairs of postcloacal papillae. The spicules are unequal in size. The left spicule is larger than the right spicule. The tail of the female ends in a simple point.

 

Life Cycle- Only few microfilarial larvae are found in the blood. Intermediate hosts are different species of mosquitoes and infective larvae are produced in 12-16 days. Definitive host is infected by the bite of infected mosquito. Prenatal infection has been recorded for a number of Setaria species.

 

Pathogenesis and Symptoms- Adult parasites are found in the peritoneal cavity and are less pathogenic although they may cause a mild fibrinous peritonitis. S. digitata can cause eosinophilic granulomatous lesions in the urinary bladder. Sometimes it is found in the eye and causes blindness in horse. Sometimes it is also found in the central nervous system and causes damage and paralysis of organs.

 

Diagnosis- The signs vary according to the site of the lesion and may be slight if relatively unimportant nervous areas are affected. Clinical signs may vary from muscular weakness and ataxia to paralysis and death.

Treatment – Levamisole- 7.5mg/kg b.wt.per day for three days.

Diethyl carbamazine- 25-100mg/kg b.wt /day for 3-13days regularly.

 

Suborder-Camallanata

Superfamily-Dracunculoidea

Family 8- Dracunculidae

Genus- Dracunculus

Species- D. medinensis (Guinea Worm, Serpent Worm, Dragon Worm or Medina Worm)

 

Location and Host- Parasites are found in the subcutaneous tissues of man and rarely observed in dog, horse, cattle and other animals in India, Palestine, West Africa, North East Africa and Middle East.

 

Morphology- The males are 12-29mm long and females are 100-400cm long and 1.7mm thick and have no vulva.

 

Life Cycle- Parasites are viviparous and intermediate host is Cyclops. The adult female lives in the subcutaneous connective tissue and thus cutaneous swelling occur. Later this swelling is converted into ulcer which develops around the anterior extremity of the parasite. When this ulcer comes in contact with water the uterus is prolapsed through the anterior end of the worm or through its mouth and ruptures. After rupture of the uterus a mass of larvae is discharged, which are 500-750µm long into the water. These larvae are taken by the intermediate host Cyclops. Infection of final host takes place through drinking water which contains the infected Cyclops and the worm develops to maturity in about one year.

 

Pathogenesis and Symptoms- Disease caused by this parasite is called Dracunculiasis or Dracuntiasis. Shortly before the host may show signs such as itching and rise of temperature and blister formations on the skin.

 

Diagnosis –By finding the blister as well as from the symptoms of the disease.

 

Treatment- The classical method of treatment is to remove the worm, which must be done carefully without breaking it. It is usually tied to a small stick and gradually rolled up in the course of a few days or weeks.

Niridazole –25mg/kg/day for ten days.

Thiabendazole- 50mg/kg/day for two or three days.

 

 

 

 

 

 

 

 

 

 

 

Subclass- Aphasmidia or Adenophorea (Chitwood, 1958) (Phasmid absent, caudal gland present or absent. Caudal alae usually absent)

Order – Enoplida

Superfamily- Trichuroidea

Family 1- Trichuridae

Genus- Trichuris (Whipworm)

 

T. ovis	Goat, sheep, cattle and other ruminants.
T. discolor	Ox, sheep zebra and buffalo.
T. globulosa	Camel, sheep goat, cattle etc.
T. suis	Pig and wild boar.
T. serata	Cat.
T. trichiura	Man.

 

 

Fig. Trichuris Spp.

Genus 1- Trichuris ovis

 

 

Location and Host- Parasites are mostly found in the caecum of the goat, sheep, cattle and many other ruminants.

 

Morphology- The male parasite measures 50-80mm long. The anterior end constitutes three-quarters of the length. The female is 39-70mm long, of which the anterior end forms two- thirds to four-fifths. Hence, the anterior part of the body is long and slender, while the posterior part is much thicker. The hind end of the male is curved and there is only one spicule surrounded by a protrusible sheath, which is usually armed with five cuticular spines. The vulva is situated at the beginning of the wide part of the body. The eggs are brown, barrel shaped with a transparent plug at either pole, measure 70-80 by 30-42µm in diameter including the plugs. They contain unsegmented embryo when laid.

 

Genus 2- T. discolor: Occurs in the caecum and colon of zebu, buffalo, sheep and goat in Europe, South and East Asia. Females are orange-yellow in colour and eggs measure 60-73 by 25-35µm in diameter. The eggs develop to the infective stage larvae after about three weeks under favorable condition. The development may be much more prolonged at low temperature. Development of eggs is related to soil moisture and temperature. The host is infected by ingestion the eggs. The liberated larvae penetrate the anterior part of the small intestine for two to ten days before they move to caecum where they develop directly into adults. The prepatent period of T.ovis is seven to nine weeks; of T. vulpis is 11-12 weeks and of T. suis 6-7 weeks.

 

Pathogenesis and Symptoms- Disease cause by this parasite is called Trichuriasis. They can produce an acute or chronic inflammation, especially in the caecum of the sheep, goat, cattle, dog and man. Haemorrhages, dysentery, anaemia, anorexia and loss of weight, some time infection terminating in death can be observed in this disease. In human prolapse of rectum has occasionally been observed in massive Trichuriasis.

 

Diagnosis- This is made by demonstration of the characteristic barrel shaped eggs in the fecal examination.

Treatment- Mebendazole- 100mg twice aday for 3to 5days.

N-butylchloride- 0.1-1.0ml/kg, i/v given hourly for five hours for dog.

Methyridine – 200mg/kg b.wt. for sheep and cattle.

Fenbendazole- 5-20mg/kg b.wt.

Trichlorophen-75mg/kg b.wt.

Levamisole-7.5mg/kg b.wt.,s/c.

Teramisole- 15mg/kg b.wt. orally mixed in the feed.

 

Family 2- Capillariidae

Genus: Capillaria

 

C.  annulata	Mostly found in oesopahagus of fowl and other birds. Life cycle is indirect.
C. bovis	Found in small intestine of sheep, goat and cattle. Male: 13mm long, female: 12-20mm long and life cycle is direct.
C. caudinflata	Found in duodenum and ileum of fowl, pigeon and other birds. Life cycle is indirect.
C. hepatica	Found liver of rodent, mostly rat and rarely also infects dog and cat.
C. obsignata	Found in small intestine of fowl and turkey.

 

Genus 1- C. bovis

 

Location and Host- Parasites are mostly found in small intestine of sheep, goat and cattle and are comopolitan in distribution.

 

Morphology- The worm is closely related to the genus Trichuris. They are small and slender and the posterior part of the body is not conspicuously thicker than the anterior part. The males are 8-13mm long and females are 12-30mm long. The eggs are colourless barrel shaped with the sides rarely parallel, the bipolar plugs do not project and they measure 45-50 by 22-25 µm in diameter.

 

Life Cycle- The life cycle is direct. The eggs are unsegmented when laid and develop to the first larval stage in nine to fourteen days. The final host is infected after the ingestion of infective eggs of the parasite.

 

Genus 2- C. caudinflata

 

Morphology- Parasites are found in the duodenum and ileum of the fowl, pigeon and related wild birds. Males are 9-14mm long and females are 14-25mm long. The oesophagous is almost half as long as the body in the male and one third as long in the female. The tail of the female is cylindrical up to the end. The vulva has a conspicuous projection appendages. The eggs are 47-65 by 23 µm in diameter with thick, finely sculptured shell.

 

Life Cycle- In case of C. caudinflata the intermediate host are different species of Earthworm. The eggs are swllowed by the earthworm and larvae hatch. Birds are infected by eating the infected earthworms. The prepatent period is three weeks.

 

Pathogenesis  and Symptoms- Light infection produces only mild inflammation and thickening of the crop of infected birds. In heavy infection there is a marked catarrhal inflammation and secretion of mucosa. The birds are emaciated and weak.

 

Genus 3- C. hepatica

 

Location and Host- Parasites are mostly found in liver of rodent particularly rat and mouse but sometimes dog and cat may also be infected by this parasites.

 

Morphology- Morphology is similar to C. caudinflata.

 

Life Cycle- The life cycle is direct. The eggs are unsegmented when laid and develop to the first stage larvae nine to fourteen days after infection; then they infect the host. The life cycle is unsual. The unembryonated eggs must be released from the liver by a predator, often called an Intercalary host, or by cannibalism and the eggs are passed in the faeces of the predator cannibal. From embryonation to the infective stage it takes four weeks at 30⁰C. Decomposition of dead carcasses is also important in egg dispersal. Infection takes place by ingestion of food contaminated by eggs shed by the Intercalary or cannibalistic host or from a decomposed infected carcases.

 

Pathogenesis and Symptoms- Light infections in domestic animals or man may be inapparent. The heavy infection may cause acute or subacute hepatitis with peritonitis, ascites and eosinophilia.

 

Diagnosis- By demonstration of eggs in faeces.

 

Treatment- Mebendazole-400mg/day for 20 days.

Levamisole- 30mg/kg b.wt. single dose.

 

Superfamily- Dioctophymatoidea

Family 3- Dioctophymatidae

Genus- Dioctophyma

Species- D. renale (Syn. Eustrongylus gigas)

 

Location and Host- Parasites are found in the kidney and other organs of the mink, dog, fox and other wild carnivores and occasionally found in the pig, horse, cattle and man.

 

Morphology- The male parasite measures up to 35cm long and the female up to 103cm long (largest nematode known). The worms have a blood-red colour. The tail of the male bears a terminal, cupshaped bursa without rays. The spicule is single. The eggs are barrel-shaped and brownish yellow in colour and the shell is pitted except at the poles. They measure 71-84 by 46-52µm in diameter.

 

Life Cycle- The eggs are passed in the urine of the host and develop slowly in water requiring one to seven months according to the temperature. They do not hatch until they have been swallowed by the intermediate host but the eggs may be viable for five years. Free living earthworm species act as the intermediate host. The definitive hosts are infected by ingestion of the intermediate host. The paratenic host may occur in the life cycle, which are frogs and it becomes infected by the ingestion of infected earthworms. In the final host the infective larvae penetrate the intestinal wall and initially develop in the body cavity and then penetrate the kideney. The worms apparently enter the pelvis and destroy the parenchyma.

 

Pathogenesis and Symptoms- Frequently no signs are seen since the normal kidney can serve the needs of the body. In severe cases animal shows signs of kidney trouble together with nervous signs. Retention of urine and death from uraemia may also occur. In man renal colic, pyuria and haematuria also seen. Sometime parasite in abdominal cavity may causes chronic peritonitis.

 

Diagnosis- By finding the eggs in the urine if parasite is present in the kidney

 

Treatment- The worm may be removed surgically.

 

Order-Trichocephalida

Suborder- Trichurata

Family 1- Trichinellidae

Genus- Trichinella

Species- T. spiralis

 

 

Fig. Trichinella spiralis

Location and Host- It starts as an intestinal parasite, later found in the muscles of man, pig, rat and other mammals.

 

 

Morphology- The male is 1.4-1.6mm long and the female 3-4mm long. The body is slender and the oesophagial portion is not markedly longer than the posterior part. The hind end of the male bears a pair of lateral flaps on either side of the cloacal opening, with two pairs of papillae behind them. There is neither a spicule nor a sheath. The vulva is situated near the middle of the oesophageal region. The eggs measure 40 by 30um in diameter and contain fully developed embryos when present in the uterus of the female so, parasite is viviparous.

 

Life Cycle- The life cycle is initiated when muscle containing encysted larvae are ingested. These are liberated within a few hours by the digestive processes and the first two moults are completed within 26 hours and the fourth moult is within two days in the small intestine of the host. Development of adult stage is rapid, being completed in four days. Copulation occurs about 40 hours after infection. After copulation has taken place in the intestine, the males die and the females penetrate the mucosa via crypts of Lieberkuhn and some may reach the lymphal spaces. The first larvae which are about 0.1mm long enter the lymph and pass in it by way of the throacic duct to the left superior venacava and thus the reach in the blood, by which they are distributed all over the body. They develop further especially in the voluntary muscles, especially those of the diaphragm, tongue, larynx, eye and the masticatory and intercostal muscles. They have also been found in the liver, pancreas and kidney. The larvae enter in striated muscle fibres and become surrounded by a capsule formed from the muscle fibre. The larvae grow rapidly and after 30 days they measure 800-1000µm in length and have begin to coil inside the cell. Calcification begins after six to nine months but the larvae then may live for several years. In the cysts the larvae cannot develop further and infection occurs when infected meat is ingested by final host.

 

Pathogenesis and Clinical Signs- The parasite is of principal importance in human medicine. The most important pathogenic effects are produced by the larvae in the muscles. Heavy infections may lead to death, especially through paralysis of the respiratory muscles. The clinical signs are diarrhoea, fever, stiffness and pain in the affected muscles and some time oedema of the face and deafness.

 

Diagnosis- Oedema of the eyelid and face. The adult worms occasionally are found in the face. Larvae may be demonstrated in muscle taken for biopsy.

 

Treatment- Thiabendazole-25mg/kg b.wt. given twice a day for five to ten days.

 

 

 

PHYLUM – ACANTHOCEPHALA

 

 

The Acanthocephala are a group of parasitic worm, which are closely related to the Nematoda.

 

 

1. The Acanthocephala are commonly called ‘Thorny-Headed Worms’.
2. The body is mostly cylindrical.
3. Anterior part of the body consists of an evaginable proboscis, which is a hollow, cylindrical or oval in structure and is armed with transverse or longitudinal rows hooks.
4. The body covering or tegument has five layers and its absorptive surface is considerably expanded, 20-62 fold by invaginations of the outer plasma membrane into lacunar canals and vesicles.
5. Like tapeworms Acanthcephala are devoid of an alimentary canal throughout their lives.
6. Sexes are separate. The male has two testes which are tandem in position. The vasa-deferentia unite to form an ejaculatory duct and this opens through a penis which projects into an evaginable sac or bursa at the posterior extremity of the body. A group of cement glands or prostate glands are connected with the ejaculatory duct. They secrete a substance which protects the vulva of the female after copulation.
7. The size of male is much smaller than the females.
8. Parasites are oviparous.
9. The life cycle is completed in two or more host. The intermediate host is usually an Arthropod.
10. Acanthocephala are all intestinal parasites, found in all classes of vertebrates, though especially common in fishes and birds.

 

 

 

Acanthocephala Orders
Palaeacanthocephala	Archiacanthocephala
Family: Polymorphidae	Family: Oligacanthorhynchidae
Usually small worms with a cylindrical body e.g. Polymorphus, Filicollis	Usually large to medium sized worms. Proboscis is not retractile e.g. Macrocanthorhynchus, Oncicola

 

 

 

 

 

Genus 1 – Polymorphus boschadis (syn. Profilicollis minutus)

 

Geographical Distribution – Worldwide

 

Location and Host – Adult parasite occurs in the small intestine of the duck, swan, goose and various wild aquatic birds.

 

Morphology – Males are about 3 mm long and females are upto 10 mm long and they are an orange colour when fresh. The cuticle is spiny anteriorly, and behind this region the body is constricted. The proboscis has 16 longitudinal rows of seven to ten hooks each. The testes are oval and situated diagonally, the cement glands are elongated. The eggs are spindle shaped and measure about 110 by 19 µm in diameter. The embryo has a yellowish red color.

 

Life Cycle – Cystacanth develops in the ‘Fresh Water Shrimp’ the amphipod crustacean Gammarus pulex and possibly also in the crayfish Potamobius astacus. The final host is infected by ingestion of infected intermediate host. The worms are located on the posterior part of the small intestine, where they penetrate deeply into the mucosa with their proboscis.

 

Pathogenesis and Symptoms: At the point of attachment small nodules can be seen from the peritoneal surfaces. The parasite produces Cachexia, inflammation of the intestine and anemia. Heavy infections can cause severe losses in colonies or domestic and wild duck, geese and swans.

 

Diagnosis – By finding the egg in faecal examination.

 

Treatment – Carbon tetrachloride at a dose of 0.5 ml/kg.

 

Prophylaxis – The birds have to be kept away from water harboring infected intermediate host. Since migrating birds are usually the original source of infection attempts should be made to restrict their entry to breeding grounds.

 

 

Genus 2- Filicollis anatis

Location and Host – Adult parasites are found in the small intestine of the duck, goose, swan and wild aquatic birds.

 

Morphology – The male is 6-8 mm long and white in colour, the female is 10-25 mm long and yellowish in colour. The male has an ovoid proboscis with 18 longitudinal rows of 10-11 hooks each and the anterior part of the body is armed with small spines. The female has a long slender neck, while the proboscis is globular in shape and about 2-3 mm in diameter. There are 18 rows of 10-11 hooks each arranged in a star shaped pattern at the apex of the proboscis. The eggs are oval and measure 62-70 by 19-23 µm in diameter.

 

Life Cycle – The eggs are released in the feces of the infected host and the larval stages develop in Isopods and Crustaceans such as the Water Louse Asellus aquaticus (Isopods). The final host is infected by the ingestion such infected Isopods and worms grow to adults in about four weeks.

 

Pathogenesis and Symptoms – The parasites are found in the middle portion of the small intestine and also further back in severe infections. While the male attaches its proboscis in the mucosa, female worm pierces through the mucosal and muscular layer of the wall so that its proboscis comes to lie directly underneath the peritoneum. In some cases the peritoneum may even be ruptured. The parasites are obviously harmful as they cause emaciation and frequently the death of their hosts.

 

Diagnosis – By finding the eggs in the feces.

 

Treatment – Same as Polymorphus boschadis

 

 

Order- Archiacanthocephala (Meyer, 1931)

Family- Oligoacanthorhynchidae

Genus -1 Macrocanthorhynchus hirudinaceus

 

Geographical Distribution – Asia, Africa and America.

 

Location and Host – Adult parasites are found in the small intestine of domesticated pig and wild boars and also sometimes recorded from the ileum of man.

Morphology – The worms are usually more or less curved and have a pale reddish colour.  The male is up to 10 cm long and the female up to 35 cm or more and 4-10 mm thick. The cuticle is transversely wrinkled. The proboscis is relatively small and bears about six transverse rows of six hooks each, which decrease in size backwards. The eggs measure 67-110 by 40-65µm and have four shells of which the second is dark brown and pitted.

 

Lifecycle – The eggs are passed in the feces of the pig and are very resistant to cold and dryness, being able to live for several years. A number of genera in the dung beetle family Scarabaeidae act as intermediate hosts (Melolontha, Cetomia, Phyllophaga, Cotinus, Scarabeus and water beetles, Tropisternus). These become infected when they feed on manure and infected soil. The young worms eventually become encysted in the body caving of the insect. Pigs become infected by ingesting either the grubs or the adult beetles which harbor the infective stage of the worm. Development in the pig takes two to three months. A female lays about 260,000 eggs per day and lays for about 10 months.

Pathogenesis and Symptoms – The parasites penetrate with their proboscis deeply into the intestinal wall where they produce inflammation and granulomas at the site of attachment. Rarely, perforation and death from peritonitis occurs. Severe infection may cause slow growth or emaciation.

 

Diagnosis- By finding the eggs in the feces.

 

Treatment – Carbon tetrachloride, Tetrachloroethylene and Nicotine sulphate have been used.

 

Prophylaxis – The pigs should be prevented from ingesting the larvae or adults of the intermediate hosts. Where pigs are kept in sites on small runs regular removal and suitable disposal of feces will assist in reducing the infection.

 

 

Genus 2- Oncicola canis

 

Geographical Distribution – Mostly occurs in the North and South America.

 

Location and Host – Adult parasites are mostly found in the intestine of domesticated dog, cat and other wild carnivorous animals.

 

Morphology – The size of the male is about 6-13 mm long and the female is about 7-14 mm long, both sexes being 2-4 mm thick. The shape of the body is roughly conical, tapering backwards and has a dark grey colour. The proboscis bears six transverse rows of six hooks each. The anterior hooks have the shape of a taenoid hook, while the posterior ones resemble rose thorns. The lemnisci are very long and slender. The testes are oval, tandem and situated in the anterior half of the body. The eggs are oval, brown colored and measure 59-71 by 40-50 µm.

 

Life Cycle – Probably an arthropod acts as an intermediate host. Immature forms about 4 mm long, which are believed to belong to this species, have been found  encysted in the connective tissue and muscles of the Armadillo (Dasypus novemcinctus) and in the epithelium of the oesophagous of Turkeys. These presumably act as paratenic hosts and up to 10% of turkey poultry have been found infected in Texas.

 

Pathogenicity and Symptoms – Infection may be common and 31% of dogs have been found infected, but the parasite is rarely of clinical importance. The worms lie with their proboscis deeply embedded in the intestinal wall, penetrating right through to the peritoneum.  The parasites may possibly cause rabiform signs in dogs. Such were observed in a dog which harboured about 300 worms.

 

Diagnosis – Diagnosis can be made by finding feed eggs in feces.

 

Treatment and Prophylaxis- Unknown.

 

PHYLUM – ANNELIDA

Class – Hirudinea

 

Characters

1. The Hirudinea or leeches are soft-bodied and usually elongated and dorsoventrally flattened worms with a true metameric segmentation.
2. The number of metameric segments in each specimen is 33 or 34 and these segments are externally subdivided by transverse lines.
3. The anterior region is differentiated to form head which bears triangular anteroventral suckers.
4. The posterior seven segments form a large sucker and the anus is situated on the dorsal aspect of the hind end.
5. The ninth, tenth and eleventh segments form the clitellar organ which serves to secrete the cocoon.
6. The worms are hermaphrodite. These are several to many testes and one pair of ovaries. The median male genital opening is on the tenth segment and the median female genital opening on the eleventh segment.
7. Two orders of leeches are recognized, Gnathobdellidae and Rhynchobdellidae. In the Gnathobdellidae the anterior sucker contains the oral apearture, which is provided with three strong toothed jaws. In Rhynchobdellidae they have a protrusible proboscis, but no jaws. There is a short esophagus and a stomach (crop), which is usually provided with a paired, segmentally arranged, blind sacs for storage of ingested blood, followed by an intestine and a rectum.
8. The body cavity is filled with lacunar tissue. The excretory organs are segmentally arranged nephridia. 
9. Leeches are occasional parasites and feed on blood of various animals to which they attach themselves and drop off after being engorged with blood. They have pharyngeal glands which secrete an anticoagulatory substance that interferes with the action of anticoagulant of the animal’s blood.
10. Leeches are vectors of certain diseases such as pathogenic organism of Rinderpest and certain Trypanosomes and their relatives are parasitic in marine and freshwater fish.

Order Gnathobdellidae has may species of veterinary and medical interest.

 

Genus 1 – Hirudo medicinalis

 

This parasite is 8-12 cm long and 1-2 cm wide. The dorsal surface is grayish-green with six longitudinal reddish bands. The ventral sucker is olive-green with a black band on either side. They are found in marshes, streams and pools of water in Europe and North Africa.  It is of little interest as a possible parasite and occasionally animals may be come infected.

 

Genus 2– Haemadipsa

 

Various species of Haemadipsa mostly live on trees, shrubs rocks etc. and attach themselves to passing animals and human beings in the tropical forest of Asia and South America. These leeches are very active. Their bite is not painful, but the wounds may bleed for a long time. When groups of these leeches attach themselves to legs of horses, animals and the ankles of human beings, it causes severe irritation and anaemia and emaciation may result.

 

Genus 3- Hirudinaria granulose (Indian Leech)

 

This is commonly known as Indian cattle-leech and is distributed in Nepal, India Burma and Srilanka.  It is commonly found in freshwater ponds, ditches, paddy fields, swamps lakes and sluggish streams. They are found as an ectoparasite and are sanguivorous as they feed on the blood of cattle. The size of a mature leech may reach about 30 to 35 cm long. It has a soft, smooth, slimy, vermiform, elongated dorsoventrally flattened body. The colour of the body on the dorsal side is bright with green shade dorsally and orange-red ventrally with longitudinal lines of orange-red laterally. The elongated body is divided into metameres which are usually thirty-three in number. There are two suckers, the anterior sucker is called cephalic sucker and another sucker is called posterior sucker.

 

The bites of Hirudinaria species is little painful, and the wounds may bleed for long time and may cause anaemia and emaciation. H. moniliensis, which is a common Indian paddy field leech, is said to play the role of vector of pathogenic organism of Rinderpest disease. Leeches in water can be killed by means of Copper sulphate.

 

Genus 4- Limnatis nilotica

 

Mostly found in pools of water country plants in Europe and North Africa. Adult worms live at the bottom in the mud; young leeches occur near the surface. The young leeches can readily be swallowed by animals drinking in such ponds and infection occurs chiefly in dry season when water is scarce. They infect mostly cattle, buffaloes, equines, sheep, dogs and pigs and man may also become infected. These parasites attach themselves in the pharynx and nasal cavities, where they may stay for days or even weeks. The size of the parasite is about 8-12 cm long and the body is soft. The dorsal surface is fairly dark brown or greenish and usually has several longitudinal rows of black spots. The ventral surface is darker than the dorsal and there is frequently an orange band on either side. The anterior lip has a longitudinal groove on its inner surface.

 

Pathogenesis- They suck blood so that in serve infections anemia and lack of condition may occur. More serious is the frequent occurrence of edema in the affected areas. Blood or bloody froth may often be seen extruding from the mouth or nostrils of the animal. There is dysponea and in severe cases the neck is extended and the mouth is half open. Oedematous swellings may be seen in the parotid and intermandibular regions. Death may be caused by asphyxia, and it may be sudden as a result of edema of the glottis.

 

Diagnosis- Made from clinical signs and by finding the parasites in the pharynx.

 

Treatment- The injection of chloroform water gives very success full results. An elastic catheter is passed through the inferior nasal meatus and to the free end a 60ml syringe containing the solution is attached. The solution is injected slowly while the catheter is revolved, the head of the animal being held in a horizontal position. In extreme cases tracheotomy may be necessary.

 

Prophylaxis- Animals should be given water in clean troughs. Leeches in water can be killed by means of Copper sulfate.