Pathogenesis of an Avian Reovirus Isolate Displaying Enteric and Arthritic Tropisms

Avian reoviruses (ARVs) within genetic cluster (GC) 2 represent a large, heterogenous group of currently circulating ARVs that have been isolated from clinical cases of tenosynovitis and malabsorption. In this study, the pathogenesis of an ARV GC 2 isolate was investigated via quantitative reverse transcriptase PCR (RT-qPCR), in situ hybridization (ISH), and histopathology, following oral or footpad inoculation. RT-qPCR detected ARV within the digital flexor tendon, heart, lung, liver, spleen, kidney, duodenum, cecum, cloacal bursa, and thymus. The highest viral RNA load was observed within the intestinal tract between 36 and 72 hr postinoculation (hpi). ISH demonstrated ARV within villous enterocytes throughout the intestines, follicle-associated epithelial (FAE) cells of the bursa, and the synovial membrane of the tendon. Histopathology within the intestine consisted of rare syncytia with negligible inflammation, whereas marked inflammation was present within the synovial tissues. The identity of infected enterocytes as avian "M cells" or infected synovial lining cells as macrophage-like synoviocytes (MLS) could not be histologically determined. However, the susceptibility of these varied cell types to infection with an ARV GC 2 virus demonstrates simultaneous potential enteric and arthritic roles in the pathogenesis of these reoviruses.