An outbreak of post-vaccinal suspected distemper-like encephalitis in farmed ferrets (Mustela putorius furo)

Abstract

Two outbreaks of an encephalitis apparently induced by an attenuated live distemper vaccine occurred in a large ferret breeding establishment in New Zealand. Approximately 350 of 6,000 young ferrets 16-22 weeks old died. Many were found dead with no premonitory signs, others showed severe neurological signs. Some with central nervous system (C.N.S.) signs recovered. Pathological examination showed no gross abnormalities except for a few with mild conjunctivitis, rhinitis and lung emphysema. Microscopically there was a moderate to massive non-inflammatory necrosis of hippocampal nerve cell bodies. In those animals which survived for several days with CNS signs there was also a mild to moderately severe non-supportive encephalitis, and in some of these distinct neuronal intranuclear and intracytoplasmic eosinophilic inclusion bodies were seen. Some ferrets also had a bronchiolitis with intracytoplasmic eosinophilic inclusion bodies in bronchiolar epithelium. All these lesions suggest that a distemper like condition was involved. About half of the ferrets also had a mild to severe inflammatory myocardial necrosis.