PATHOGENESIS OF EXPERIMENTALLY-INDUCED RABIES IN DOMESTIC FERRETS

Objective-To determine susceptibility, incubation and morbidity period s, clinical signs, serologic response, and excretion of virus in domes tic ferrets inoculated with rabies virus. Animals-55 domestic ferrets. Procedure-5 groups of 10 ferrets were inoculated with rabies virus, I M, at doses of 10(5.5) to 10(1.5) median mouse intracerebral lethal do se. Ferrets were observed and behavior was recorded. Rectal temperatur e, body weight, and samples from the oral cavity and samples of saliva and blood were obtained. Virus isolation was attempted, using intracr anial mouse inoculation and cell culture. Virus neutralizing antibodie s were determined by rapid fluorescent focus inhibition test. Ferrets were euthanatized immediately if clinical signs were severe. Fables wa s confirmed by direct immunofluorescent antibody test. Results-Mean in cubation period was 33 days (range, 16 to 96 days). Clinical signs inc luded ascending paralysis, ataxia, cachexia, bladder atony, fever, hyp eractivity, tremors, and paresthesia. Mean morbidity period was 4 to 5 days (range, 2 to 10 days). Virus antigen was detected in brain tissu e from all clinically rabid ferrets. Ferrets given the highest viral d ose were euthanatized and had VNA; ferrets receiving the next dilution also were euthanatized, but only 4 had seroconverted. Of 17 ferrets t hat survived, 5 seroconverted. Survivors remained clinically normal ex cept for 1 that recovered with severe paralytic sequelae. Rabies virus was isolated from the salivary gland of 1 ferret that was euthanatize d. Conclusions and Clinical Relevance-Rabies should be considered as a differential diagnosis in any ferret that has acute onset of paralysi s or behavioral changes and a condition that rapidly deteriorates desp ite intense medical intervention.