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

This is a review of a five-year study (from 1985 to 1989) that examined horse deaths at a veterinary school, specifically focusing on neurological diseases and instances of rabies.

Research Context and Method

• This retrospective study was undertaken to examine the occurence of various neurological diseases in horses, alongside cross-checking for incidences of equine rabies.
• The study covered a five-year period from 1985 to 1989 and looked at horses that had been necropsied (examined post mortem) at a veterinary school’s diagnostic laboratory which was located in North America, in an area where raccoon rabies was endemic.

Findings and Observations

• Over the course of the study, it was found that more than 20% of the horses examined showed clinical neurological signs. The most common disorders found were equine protozoal myeloencephalitis (a disease affecting the brain and spinal cord caused by the parasite Sarcocystis neurona) and cervical stenotic myelopathy (also known as wobbler syndrome).
• Despite the prevalence of raccoon rabies in the area, only four instances of equine rabies were diagnosed over the course of the five-year study. The research team thoroughly documented the gross microscopical and immunohistochemical findings from these four cases of rabies.

Tests and Validations

• The researchers also used immunoperoxidase tests to check for the presence of rabies antigen in another 35 horses diagnosed with non-specific encephalitis (brain inflammation) or encephalopathy (brain disease). None of these tests returned a positive result.
• Based on these findings, the study inferred that immunoperoxidase testing can be considered a valid method for diagnosing rabies when fresh tissue samples are not available for conducting a fluorescent antibody test.

Conclusions

• The study concluded that it is unlikely that any cases of equine rabies were overlooked by the diagnostic laboratory during the investigation period. This is significant since the location of the veterinary school was in an area where raccoon rabies was prevalent.