Experimental histopathologic study of the lesions induced by serotype 793/B (4/91) infectious bronchitis virus

The study was conducted to determine the type, frequency and severity of gross, histopathologic changes, effect of route of infection and also, tissue tropism of serotype 793/B (4/91) infectious bronchitis virus. 20 day-old specific pathogen free chicks were inoculated intra-tracheally and intra-orally with 793/B serotype and lesions studied histopathologically at interval up to 10 days post-inoculation (pi). The mortality was 7.5% in the IBV-inoculated groups but not in the controls one. Grossly, a small amount of clear mucus and slight congestion were present in the lumen of the trachea, also congestion observed in the lungs. Swollen and pale kidneys due to IBV infection were slightly severe. At the early stage of infection, the histopathological changes in the lungs, kidneys, intestines, were similar in both groups. So, the route of infection with IBV may affect the incidence of disease is not supported. At the late stage of infection, the changes of kidneys were more severe and characterized by nephritis with formation of lymphoplasmacytic nodules in kidneys and other feature of infection with this serotype on intestine was enteritis of both IBV-inoculated groups.