Pathological and molecular findings of avian reoviruses from clinical cases of tenosynovitis in poultry flocks from Brazil

Avian reoviruses (ARVs) can infect a variety of species worldwide. Birds can present stunting syndrome, respiratory and/or enteric diseases, immunosuppression, malabsorption, viral arthritis/tenosynovitis, and even secondary infections by other microorganisms. Flaws in conventional vaccines and the increase in the diagnostic rate of disease in the last 5 yr suggest the emergence of pathogenic ARVs in the poultry flocks worldwide. This study aimed to characterize birds lesions and to detect/genotype ARVs from a severe outbreak of tenosynovitis in broiler poultry flocks from Brazil. Tissue samples of lesions on pelvic limbs of broiler chicken were collected in poultry flocks with a high condemnation rate of carcasses due to lesions and submitted to histological and molecular analysis. Major gross pathological lesions included marked swelling, edema, and hemorrhages. Serous exudate was present between the tendons and hock joint. Histological examination demonstrated necrosis and inflammation of muscle fibers, mixed inflammatory infiltrate was observed in subcutaneous tissue and tendon sheaths. ARVs RNA was detected in 5 samples tested by polymerase chain reaction. These samples were also genotyped and demonstrated the occurrence of strains of the ARVs lineages II and V in the flocks. These results suggest that theses field ARVs, genetically distant from previously characterized strains, are associated to tenosynovitis and present in commercial Brazilian poultry flocks.