Special Veterinary Pathology

COCCIDIOSIS

Definition

• Coccidiosis is an acute or chronic haemorrhagic enteritis affecting cattle, rabbit and poultry characterized by invasion and destruction of intestinal epithelium, diarrhoea, dysentry caused by coccidia

Aetiology

• Eimeria zurnii and E.bovis - caecum, colon and ileum of cattle
• E.arloingi –Small intestine of sheep and goat
• E.canis and Isospora bigemina – Small intestine dog and cat
• E.stiedae – Intra hepatic bileduct of rabbit
• E.tenella – caecum of fowl
• E.necatrix – Small intestine of fowl
• Eimeria burneti -Rectal coccidiosis
• E.debleicki and Isospora suis- Small intestine of swine
• E.truncata - Renal tubule of geese

Pathogenesis and life cycle

• Oocyst which are the resistant, mature coccidia are voided in faeces

Eimeria sp.- Oocyst

• Inside oocysts, sporozoites develops which is ingested by a susceptible animal
• The sporozoites escape out of oocyst and invade the intestinal epithelium and multiply asexually called schizogony, forming merozoites
• Later, asexual multiplication stops and merozoites differentiates into male (microgametocyte) and female (macrogametocyte).
• The union of these two produces oocyst which ruptures epithelium and is passed out by the faeces.

Clinical signs

• Dysentry with tenesmus leading on to anaemia, dehydration and emaciation

Lesions

• The harm done to the host by the destruction of epithelial cells
• The surviving epithelium proliferate and hyperplasia manifested by enlargement of villi which may show papillary projections and these cells are full of parasites
• Mucous membrane is thickened, oedematous, denuded and haemorrhagic

In rabbits

• E.stiedae affects intrahepatic biliary epithelium of rabbits
• Cocidiosis of liver or intestine may be observed
• Liver is studded with small to larger nodules which may be round and grey in colour
• The liver is necrosed with nodules containing large number of coccidia.
• In the early lesions, there is a destruction of biliary epithelium but when the course of the disease is longer, proliferation of the epithelium is the main feature and this may be thrown into papillary folds resembling adenomatous hyperplasia

Hepatic coccidiosis- Oocysts and schizonts were seen

In birds

• Mortality may be 90 – 100%
• E. tenella is most pathogenic

Diagnosis

• Dysentry with straining
• Demonstration of oocysts in the faeces and tissue sections.