Use of Controlled Exposure as a Novel Method for Reovirus Arthritis/Tenosynovitis Prevention. A Preliminary Report.

Viral Avian arthritis/tenosynovitis has become in the last decade a serious economic threat to the poultry industry. Reovirus is the most important causal agent of arthritis/tenosynovitis in chickens. The early infection with reovirus causes inflammation and scarring of the gastrocnemius and flexor tendons, causing lameness, tendon rupture and deviation of the legs. Arthritis/tenosynovitis in chickens is not only a serious economic burden but also an important welfare problem to the poultry industry in many countries. Available commercial live and inactivated reovirus vaccines contain reovirus strains that belong to the same serotype (S-1133 or 1733). These strains, are antigenically different from the new emerging reoviruses and do not provide any protection against infection of the breeding flocks and transmission of the virus to the progeny. The new emerging reoviruses are more pathogenic and vertically transmitted, causing severe arthritis/tenosynovitis in broilers and breeders as young as 14 days of age. Sigma C sequencing of isolated reoviruses in Israel, demonstrated that the same group of reoviruses has been found to cause more than 90% of the cases. In order to reduce the economic and welfare impact of the disease in broiler and breeder flocks, a novel approach based on controlled exposure of the breeding flocks during rearing with a wild type live reovirus was tested. The controlled exposure of the flocks did not cause any damage to the health of the pullets, breeders or the production of eggs and chicks. The progeny of the vaccinated flocks did not show any signs of reovirus infection throughout their full production period.