Chronic Recrudescent Rabies in a Cat

In an attempt to induce nonfa-tal rabies infection, five cats and five skunks were inoculated intraperitoneally with low-passage rabies virus. Three of the skunks died of acute fulminant rabies. Only one of the cats showed any evidence of illness. The affected cat developed hind limb paresis, coarse tremors, and irritability 11 days after inoculation of the virus and survived the apparent infection with nondisabling sequelae. High rabies virus neutralizing antibody (RVNA) titers were found in the serum and cerebrospinal fluid several weeks after the onset of illness and declined subsequently, as is common in abortive rabies encephalitis. However, after the 16th week, RVNA titers in both fluids again rose, and in the ensuing year and a half very high levels of antibodies were achieved. At about 120 weeks, the clinical condition worsened, and 6 weeks later the cat was sacrificed. At necropsy, lesions found in the central nervous system were not those of classical acute rabies, but consisted of an extensive chronic destructive encephalitis. Virus could not be isolated, probably because of the coexisting high antibody level. The observations are interpreted as consistent with a chronic re-crudescent form of rabies encephalitis.