Diseases Caused by Helminth Parasites in Animals

List of three major diseases caused by Helminth parasites in animals:- 1. Hepatic Fascioliasis 2. Taeniasis in Dogs and Cats 3. Taeniasis in Cattle and Swine.

Helminth Parasite: Disease # 1. Hepatic Fascioliasis:

It is caused by members of the genera Fasciola, Fascioloides and Dicrocoelium and they are all liver flukes. The principal parasites are Fasciola hepatica, Fasciola gigantica, Fascioloides magna and Dicrocoelium dendriticum. The term hepatic fascioliasis is reserved for infestation with Fasciola hepatica.

Symptoms:

In acute cases, which are rare, the animal dies suddenly; blood-stained froth appears at the nostrils and blood is discharged from anus resembling Anthrax.

In sheep:

The sheep shows a temperature and is generally off colour. This is followed by an increasing anaemia/muscular weakness, loss of appetite, pale mucosa and oedema. Skin becomes dry and doughy to the touch, the wool is dry and falling out in patches. Debility, emaciation and general depression increase and there may be occasional constipation or diarrhoea and also fever. At this stage, death may occur.

In cattle:

The most characteristic symp­toms are digestive disturbances. Constipation is marked and faeces are passed with difficulty, being hard and brittle. In extreme stages, diar­rhoea is seen. Emaciation and weakness lead to prostration, specially in calves. Emaciation and weakness are prominent symptoms in other ani­mals.

Pathogenesis:

Very little damage is done during passage through the intestinal wall and the peritoneal cavity, although small haemo­rrhagic spots may be seen on the peritoneum where the worms attack themselves. The young flukes wandering in the liver parenchyma destroy the latter and, as they grow, the amount of de­struction increases causing important lesions.

Massive infections may cause rupture of the liver capsule and haemorrhage into the peritoneal cav­ity. The adult flukes in the bile ducts feed on liver tissue and they also produce a haemolytic toxin. It may cause cholangitis and cirrhosis of liver. The worms block the ducts and may result in jaundice.

Postmortem Lesions:

Anaemia, ascites, hydrothorax and hydropericardium, fatty degen­eration and cirrhosis of liver. The bile ducts con­tain the parasites and gall stones. The liver is congested and enlarged and shows numerous small dark red foci. Haemorrhagic foci also seen in the lungs and also peritonitis.

Diagnosis:

It is confirmed by finding the eggs in the faeces.

Treatment:

Carbon tetrachloride is the com­monly used drug. In recent years, many broad spectrum antibiotics with high efficiency are avail­able, e.g Rafoxanide, Diamphenethide, Choxanide, Ranide 20% water dispersible powder, Hexachlorophene tablets are very effective against both adult and immature flukes.

Helminth Parasite: Disease # 2. Taeniasis in Dogs and Cats:

Pathogenesis and Symptoms:

The larger parasites are more pathogenic than the smaller ones but the severity of infection is of greater importance and, as well as, the age of the host.

Tapeworms may cause colic or chronic enteritis. The animals may become voracious or appetite may be diminished Unthriftiness, a shaggy coat and emaciation are frequent. Convul­sions and epileptic form fits may occur in dogs only. Dogs often show symptoms of irritation in the abdomen by rubbing the abdomen on the ground. Irritation of anus is also noticed due to presence or ripe segments in the rectum.

Postmortem Lesions:

Croupous or haemorrhagic enteritis are seen specially in heavy infections of Echinococcus granulosus. The worms are found in the small intestines and they may
have migrated to the stomach or colon after death. Sometimes, heavy masses of worms occlude the lumen of the gut.

Treatment:

Dichlorophen, Diphenthane, Dicestal are the drug of choice and to be given in suitable doses.

Helminth Parasite: Disease # 3. Taeniasis in Cattle and Swine:

Taenia saginata (Beef Tapeworm) is the most common tapeworm of man. The matured parasite is harboured in the small intestine of man. It is a flat, white, jointed worm. From 12 to 25 (3.6 – 7.5 m) feet or more in length and usually only a single worm is present. Cattle become infected with the larval form (Cysticercus bovis) by swal­lowing eggs in food or water contaminated with infected human faeces.

The larvae penetrate the intestinal wall and develop into cysticerci in the flesh or organs. The favourite sites are in the heart and masseter muscles. The presence of these cysts in the muscles is known as “measly beef”. There are no clinical symptom in animals. Man becomes infected by eating raw or half cooked meat infected with cysticerci.

Taenia solium is quite common in India. The adult worm is 6 to 12 feet (1.8 – 3.6 m) in length. Swine become infected with the larval form by ingestion of food and water contaminated with egg from human sources. The larvae pass to the muscles and organs and become encysted (Cys­ticercus cellulosae).

The cysts are from 3 mm to 6mm in diameter. They are oval and whitish in colour. Man gets infected by consumption of cys­ticerci (measly pork) infected raw or insufficiently cooked pork and its products. Clinical symptoms in swine is negligible. Severe symptoms may develop in man as the larval form may also be found in human muscles.

Trichinosis:

In swine, natural infection does not induce symptoms. But after a heavy artificial infection, there may be high fever, diarrhoea, stiffness, colic, difficulty in eating and swallowing, dyspnoea and oedema. Swine are infected by offals of pork containing the encysted parasites.

Trichinella spiralis occurs in two stages of development, mature intestinal trichinae and lar­val trichinae which are encapsulated in muscles. The adult parasite is a round worm from 1.5 to 4 mm. in length with a pointed head and a some­what rounded tail. Its normal habitat is the small intestine of swine, rats and other mammals in­cluding man. The larval form is from 0.6 to 1 mm in length. When flesh containing the larvae is eaten by man or any animal in which develop­ment is possible, the capsule is digested and the trichinae are set free.

They become sexually ma­ture in the small intestine about the third day and, beginning with the seventh day, the females deposit the living embryos directly into the crypts of intestinal glands. These embryos are carried in the circulation to the muscles where encapsula­tion takes place.

Then calcification of the encapsu­lated trichinae begins and continues for one and half years—this makes the cyst visible. The favourite locations of the larvae are in the muscu­lar portions of the diaphragm, pharynx and the tongue and in the abdominal and intercostal muscles. Intensity of infestation with trichinae in garbage-fed swine is much greater than in grain- fed swine.

N. B.:

In man, trichinosis may be a severe and fatal disease. The usual source of infection is from ingestion of raw or insufficiently cooked trichinous pork.

Treatment:

Practically, there is no treat­ment, once the larvae are encapsulated in the muscles.

Prevention:

It consists in the thorough cooking of all pork before it is eaten by man or swine. There animals are normally fed with hotel wastes conforming pork products.