Co-circulation of multiple genotypes of ARV in poultry in Anhui, China

Background: Poultry production in China has been experiencing a high incidence of broiler arthritis /tenosynovitis caused by avian orthoreovirus (ARV) since 2013. In the spring of 2020 severe arthritis cases from broiler flocks were identified in large-scale commercial poultry company in Anhui Province, China. Methods: : Diseased organ from dead birds were sent for diagnosis to our laboratory. ARV, including seven broiler-isolates and two breeder-isolates, was successfully harvested and sequenced. Results: : Interestingly, the genotypes of ARVs isolated from infected chickens were inconsistent between different flocks or even between different houses on the same flocks. Subsequently, a total of 89.66 per cent sera samples collected from apparently healthy adult broiler flocks unvaccinated against ARV tested positive for ARV antibodies, suggesting that low and high virulence reovirus strains may be co-circulating in the farm. To this end, we collected unhatched embryos from breeders (parental generation) for pathogen tracing, the two harvested ARV breeder-isolates indicated that the factor of vertical transmission from breeders to progeny should not be underestimated for the prevalence of ARV within broiler flocks. Conclusion: The findings have implications for evidenced-based formulation of prevention and control strategies.