Detection of fowl poxvirus integrated with reticuloendotheliosis virus sequences from an outbreak in backyard chickens in India.

Fowl poxvirus (FPV) infection was observed in unvaccinated backyard chickens. A total of 15 birds were affected in a flock of 37. Pock lesions were observed on the comb, eyelids, beak and wattles. The birds appeared sick with roughened feathers and stunted growth. No mortality was recorded. DNA was isolated from scabs and polymerase chain reaction (PCR) was performed to amplify the 4b core protein gene of FPV, the envelope (env) gene of reticuloendotheliosis virus (REV) and the region of FPV flanking REV 5´ long terminal repeat (LTR). Correct-size PCR products of 578 bp, 807 bp and 370 bp, respectively, were observed in agarose gel electrophoresis. Sequence analysis of these products suggests that the virus was an FPV with a genome containing an integrated near full-length REV provirus. Given the fact that REV has been associated with immunosuppression, its presence in the genome of FPV appears to play an important role in the pathogenesis of fowl pox and presumably prolongs persistence of FPV in bird populations. In the present case, fowl pox has been observed to have persisted for about three years in fowl that were reared in backyard systems in villages.