Colibacillosis

Etiology:  Escherichia coli is a Gram-negative, lactose-fermenting, indole-positive rod.  There are many different strains of E. coli; rabbits are known to be affected by non-toxin producing, enteropathogenic E. coli (EPEC) strains as well as enterohemorrhagic (EHEC) strains which produce verocytotoxin.

Incidence:  The incidence of infection with E. coli is moderate to low.

Transmission:  Disease develops from overgrowth or consumption of excessive doses of pathogenic strains.

Clinical Signs:  Disease in neonates has its onset at 1 to 2 weeks of age.  Rabbits may have profuse watery yellow diarrhea with perineal staining (A.), dehydration, and high mortality.  In weanlings, watery yellow to brown diarrhea with perineal staining, weight loss, and dehydration are common.

Pathology:  In neonates, the entire intestinal tract is fluid-filled (B.).  Microscopically, coccobacilli are attached to effaced enterocytes in the small and large intestine, and there is mucosal edema.  In weanlings, the cecum is distended with watery contents, and there may be serosal hemorrhages.  Ileal villi are blunted, and the mucosa is edematous and infiltrated with neutrophils (C.).  Bacteria attached to effaced enterocytes are observed.

Diagnosis:  Diagnosis is performed by culture and evaluation of isolates for virulence factors.  Adherent bacteria on the intestinal mucosa of histologic sections can be identified.