The disease can occur in mice, rabbits, hamsters, gerbils, cats, rhesus monkeys. Infection is probably transmitted by ingestion of spores. Clinical signs appear suddenly. Young animals are more susceptible. The most prominent signs are profuse watery diarrhea and fecal staining of the perineum.
Affected rabbits are listless, anoretic, and dehydrated.
Rabbits which survive the acute infection sometimes develop chronic disease, the signs of which include progressive weight loss and cachexia. Lesions of Tyzzer's disease in rabbits are characterized principally by necrosis and occur in the cecum, adjacent intestine, liver and heart. The cecum and liver are consistently affected, but the heart is frequently spared. A presumptive diagnosis of Tyzzer's disease can be made on the basis of typical gross and microscopic lesions, but a definitive diagnosis depends on the demonstration of characteristic intracellular bacteria in affected tissues. Immunofluorescence may help identify B. piliformis.