Immunofluorescence and histopathological studies in cattle brain for diagnosis of rabies

Abstract

The present study was conducted with an aim to detect the rabies viral antigen in the brains of naturally infected cattle by immunofluorescence and identify the histopathological alterations of infected brain. For this purpose, a total of 29 brain samples were collected from rabies suspected cows, presented for post-mortem confirmation of rabies in the Department of Veterinary Pathology, GADVASU, Ludhiana. Gross examination of the collected brains showed the presence of severe congestions in both meningeal and cerebral blood vessels, as well, hemorrhage and edema in cerebrum and cerebellum. The immunofluorescence study revealed the presence of the rabies viral antigen, Negri bodies and the characteristic bullet shape of the viral particles. Histopathological examination revealed the presence of intra cytoplasmic inclusion bodies (Negri bodies) in the Purkinje cells of cerebellum, marked neuronal necrosis with satellitosis and neuronophagia, perivascular cuffing (PVC) with mononuclear cells (MNCs) infiltration and gliosis. On the basis of histopathology and fluorescent antibody test (FAT) rabies was confirmed in 17 (58.62%) and 20 (68.96%) cases respectively. Quantitative assessments of histomorphological alterations were moderate to severe congestion in 90% (18/20), hemorrhages in 45% (09/20), gliosis in 85% (17/20), microglial nodules in 65% (13/20), satellitosis in 85% (17/20), neuronal degeneration, neuronal necrosis in 80% (16/20) and perivascular cuffing (PVC) with mononuclear cells (MNCs) infiltration in 95% (19/20) cases respectively. PVC was most prominent (95% cases) followed by gliosis and satellitosis. Neuronophagia was reported in 90% (18/20) cases. Meningitis and edema was present in 25% (05/20) and 35% (07/20). The results of the present study indicated that rabies infection of cows could be easily diagnosed in the laboratory by immunofluorescence and histopathology. Special attention should be given to stray dogs and outdoor rearing of cows.