Detection and molecular characterization of enteric viruses in enteritis-affected commercial broiler chickens in India.

A study was conducted to detect and characterize the enteric viruses (chicken astrovirus, avian nephritis virus and avian orthoreovirus) present in flocks of commercial broiler chickens suffering from enteritis in Haryana, India. The intestinal contents were collected from 65 enteritis-affected flocks (cases) and tested by reverse transcription PCR (RT-PCR). Of these 65 cases, 35 (53.80%) were positive for a single virus and 26 (40.00%) for two viruses. The remaining four samples were negative for all three viruses tested. Of the 65 cases, 57 were positive for chicken astrovirus (CAstV) while 30 cases had avian nephritis virus (ANV). None of the cases were positive for orthoreovirus. Comparison of 12 CAstVs of this study with previously published CAstV sequences revealed nucleotide identities ranging from 73.20 to 98.00%. The nucleotide identities ranged between 83.10-95.50% when nine ANVs of this study were compared with previously reported ANV sequences. The amino acid sequences of CAstVs in comparison to previously published sequences revealed certain unique changes. Phylogeny based on polymerase gene revealed that CAstVs and ANVs of this study were under the same monophyletic clade. In conclusion, a large number of broiler chicken flocks experiencing enteritis were positive for CAstV and ANV by RT-PCR. The presence of more than one enteric virus in enteritis-affected flocks and changes at the genetic level in these viruses may affect the severity of disease.