Viral distribution in central nervors system various presentations of dog human rabies

Abstract

In order to study the viral pathogenesis of the two distinctive forms of dog and human rabies (furious and dumb encephalitic and paralytic), rabies viral antigen distribution in central nervous system was studied by immunohistochemical technique with avidin-biotin-peroxidase complex (ABC) amplification. Various regions of brain and spinal cord of rabid dogs at the early stage and of human patients were fixed in formalin and prepared for paraffin sections. Equine anti-rabies globulin was used as the primary antibody. Staining was characterized by inclusion bodies and or diffuse staining in the cytoplasm of neurons and neuroglias. Sensitivity of immunoperoxidase staining on histological section and the conventional i.e. Seller's stain, Fluorescent antibody test on brain impression smear and Mouse inoculation test were 86.7%, 40%, 100% and 100% respectively. The results showed that rabies viral antigen was distributed in neuroglias as well as in neurons in all regions of brain and spinal cord of both dogs and human rabies, and the distribution was anatomically similar in both forms of the disease regardless of the species. There was correlation between inflammatory reactions and amount of antigens or clinical forms of the disease. Viral localization was correlated with survival period, i.e. interval between onset of disease and death. Human patients as well as rabid dogs, whose survival periods were less than 7 and 5 days respectively, had greater amount of antigen-positive neurons in brain stem and spinal cord, where as those who had longer survival period had widespread dissemination of rabies antigen in the entire central nervous system. The results did not support the hypothesis that differential distribution of rabies virus and inflammation were responsible for the diversity of the manifestations in human and canine rabies. Pathogenesis thus may be multifactorial, involving immunological as well as physiological disturbances, and does not depend on viral localization. The immunoperoxidase staining using ABC technique can also be extended and applied to researches on viral or other studies in the future.