Pathotyping of infectious bronchitis virus isolated from broiler chickens showing nephropathy

Seven infectious bronchitis virus (IBV) isolates, isolated from two to three weeks-old broiler chickens were subjected for the pathotyping trial. The virus isolated from dead or sacrificed chicks produced lesions characteristic of IBV after three passages embryonated SPF chicken eggs. All the dead chicks showed pale, enlarged kidneys and urate deposit in ureters. Microscopically, kidney showed severe vascular congestion and intertubular haemorrhages. The lesions such as single cell necrosis, tubular epithelial necrosis and interstitial lymphoplasmocytic infiltration were markedly observed during 14 and 21 DPC. Nephropathogenicity of the IBV field isolates was assessed by giving score based on microscopic renal lesions induced in chicks which died due to nephritis. The isolates Ind/KA/07/1 and Ind/TN/07/2 had the highest score of 1.33. Based on the mortality and lesions produced, isolates Ind/KA/07/1 and Ind/TN/07/2 were found more virulent in nephropathogenicity.