Rabbit diseases diagnosis, prevention and control

- PROTOZOAL DISEASES

1- Coccidiosis

General: Coccidiosis is a common, widespread problem in commercial operations
and research facilities. It is an important economic and complicating disease. Coccidia may act as a co-pathogen in other infections. As with the other causes of enteritis, changes in management practices such as feeding or experimental procedures can predispose to infection and disease.

There are two forms of coccidiosis in rabbits - an intestinal form, and a hepatic form. Eimeria species commonly cause enteric disease in large groups of rabbits, especially in young animals.

Disease Forms/Subtypes

Hepatic caused by: Eimeria stiedae.
-Subclinical disease is common.

-Acute mortality is associated with large infective oocyst dose.

-When clinical disease is present, the signs are variable.

Intestinal form (Intestinal Coccidiosis)

-  Subclinical disease is common in adult rabbits. Pathogenicity varies with Species of Eimeria. All intestinal species of Eimeria appear to be pathogenic in young rabbits.

-  In adult rabbits, E. coecicola, E. irresidua, and E. magna are highly pathogenic; E. piriformis and E. media are moderately pathogenic; and E. perforans is mildly pathogenic.

 Although rabbits are cecotrophic, it is generally accepted that cecotropes do not contain infectious oocyst.

 

Transmission:
Fecal-oral. After passage in the feces, the oocysts require one or more days to sporulate.

 Pathogenesis:
-After the sporulated oocysts are ingested, sporozoites are released which invade
enterocytes and multiply via schizogony.

- One or more sexual cycles (depending on the species) takes place, then gametogony occurs and oocysts are formed and passed in the feces.
- Most Eimeria species in rabbits affect one or more segments of small
intestine; a few affect cecum or colon also.

- Parasitized enterocytes are lost resulting in superficially necrotizing enteritis. Severity of epithelial destruction and degree of inflammatory response vary considerably.
Clinical signs
Intestinal Coccidiosis

Varies from none to profuse watery, even bloody, diarrhea and death, depending

on susceptibility of host (young or not previously exposed are more susceptible),
species of causative organism, and inoculating dose. Mild or no signs are more
common. The cecum and colon contain dark green to brown, watery, foul smelling material. The mucosa is congested and edematous.
Pathology: Location of the lesions is dependent on the species involved. Destruction of
enterocytes, villous atrophy, marked heterophilic infiltration and presence of gametocytes and oocytes.

Hepatic coccidiosis

Etiology: Eimeria stiedae.
-Infected rabbits showed poor weight gains, clinical disease and even death in affected colonies.

-Weanlings are most often affected; older rabbits develop immunity.

-The liver is enlarged owing to papillary hyperplasia of the bile duct epithelium (and gallbladder occasionally) with different developmental stages of coccidia within bile ducts.

-Acute cases may show numerous miliary hepatic abscesses.

-Chronic cases develop a fibrotic response around affected ducts.

-Other organs are not infected.

Life-cycle of Eimeria stiedae.

Transmission:
After ingestion of sporulated oocysts, sporozoites penetrate intestinal epithelial cells then are transported to the liver where they invade epithelial cells lining bile ducts and undergo schizogony. After gametogony, oocysts are released into bile ducts, pass to the intestinal tract via the bile and are then passed into the feces.

 Clinical signs:
- None to anorexia, debilitation, constipation or diarrhea. May also see hepatomegaly, pendulous abdomen, icterus and death. Elevated  liver enzymes and serum bilirubin on clinical pathology.
- Hepatomegaly with multifocal, raised, yellow to pearl grey, circumscribed, 0.5-2 um foci which contain an inspissated dark green to tan material. In the liver; these are bile ducts chronically inflamed and dilated with bile and exudate.

-  Microscopic: chronic proliferative cholangitis and cholecystitis, with numerous schizonts, microgametes, macrogametes, and developing oocysts in the epithelial cells; also, oocysts in the lumen.

D.D:
Enteric Diseases: (enterotoxemia, Tyzzer’s disease, coccidiosis, and mucoid enteropathy, E.coli , salmonella)