Tyzzer's disease in muskrats: occurrence in free-living animals.

Tyzzer's disease was diagnosed in four muskrats (Ondatra zibethica) found dead over a 2 month period in a single feed-house in a Saskatchewan marsh. No dead animals were found elsewhere in the marsh, although several hundred apparently healthy animals were trapped during this period. Similarities in the pathology and epizootiology of Tyzzer's and Errington's diseases of muskrats support an hypothesis that these diseases are a single entity.