A five year (1985-1989) retrospective study of equine neurological diseases with special reference to rabies.

A retrospective study of horses necropsied between 1985 and 1989 at a diagnostic laboratory of a veterinary school in North America is documented. In this investigation over 20 per cent of the horses had clinical neurological signs. Equine protozoal myeloencephalitis (caused by Sarcocystis neurona) and cervical stenotic myelopathy (wobbler syndrome) were the most common of these disorders. The veterinary school is located in the midst of a raccoon rabies enzootic area. However, only four cases of equine rabies were diagnosed during the 5-year study. The gross microscopical and immunohistochemical findings from these rabies-positive horses are documented. Immunoperoxidase tests for detection of rabies antigen in another 35 horses with non-specific encephalitis/encephalopathy did not reveal any positive cases. Based on this investigation, it appears that immunoperoxidase is a valid method for diagnosis of rabies when fresh tissues are not available for the fluorescent antibody test. It is also concluded that no cases of equine rabies were overlooked by the diagnostic laboratory during the period under investigation.