Comparative study of very virulent infectious bursal disease virus induced bursal pathology in experimentally infected Indian native Aseel and exotic White Leghorn chicken

Abstract

Infectious bursal disease (IBD) is one of the economically important emerging diseases of poultry. Indigenous birds are believed to be resistant to classical strain of IBD virus for unknown reasons. The present study was attempted to compare the bursal pathology induced by very virulent strain of IBD virus (vvIBDV) in indigenous Aseel and exotic White Leghorn chicken (WLH). The different bursal parameters namely mean bursa bodyweight ratio (BBWR), gross pathological lesions, histopathology; immunohistochemistry of bursal tissue and the viral load in bursa were compared following vvIBDV virus infection in vaccinated and unvaccinated birds of both the breeds. The mean BBWR of unvaccinated challenged WLH was significantly greater than the control, while the pre-infection bursal index of WLH was greater than Aseel. The viral load was higher in vaccinated WLH indicating a possibility of viral replication. However, there was lack of correlation between the viral load on different days and the extent of histopathological scores in bursa of infected birds. The vaccinated birds from both the breeds showed reduced histopathological lesions than the unvaccinated ones emphasizing the protective role of vaccination. It remains interesting and important that, though the very virulent IBD virus causes disease in indigenous Aseel chicks, a faster clearance was exhibited indicating the role of some unidentified innate immune factors.