Characterization of spinal cord lesions in cattle and horses with rabies: the importance of correct sampling.

Twenty-six cattle and 7 horses were diagnosed with rabies. Samples of brain and spinal cord were processed for hematoxylin and eosin staining and immunohistochemistry (IHC). In addition, refrigerated fragments of brain and spinal cord were tested by direct fluorescent antibody test and intracerebral inoculation in mice. Statistical analyses and Fisher exact test were performed by commercial software. Histologic lesions were observed in the spinal cord in all of the cattle and horses. Inflammatory lesions in horses were moderate at the thoracic, lumbar, and sacral levels, and marked at the lumbar enlargement level. Gitter cells were present in large numbers in the lumbar enlargement region. IHC staining intensity ranged from moderate to strong. Inflammatory lesions in cattle were moderate in all spinal cord sections, and gitter cells were present in small numbers. IHC staining intensity was strong in all spinal cord sections. Only 2 horses exhibited lesions in the brain, which were located mainly in the obex and cerebellum; different from that observed in cattle, which had lesions in 25 cases. Fisher exact test showed that the odds of detecting lesions caused by rabies in horses are 3.5 times higher when spinal cord sections are analyzed, as compared to analysis of brain samples alone.