epithelial cells of the small intestines are the main sites of infection and portal of entry of the virus which quickly disseminates to other organs within a 24- to 48-hour window post infection. The tibiotarsal-tarsometatarsal (hock joint) was the site where virus replication caused the most severe damage and in some extreme cases, tendon rupture. Immune responses Humoral antibodies The sera of birds infected with avian reovirus display circulating antibodies through the validation of ELISA, agar gel immunodiffusion, indirect immunofluorescence (IIF), and virus neutralization (VN). Virus neutralization identifies type-specific antibodies, which allows for differentiation between strains of viruses through their distinct antigens. The other four tests detect group antigens. Maternal antibodies Maternal antibodies have displayed protection against the development of microscopic lesions of tenosynovitis in chicks that have been infected one day after birth. Protection provided by maternal antibodies has served as a foundation of breeder vaccination. Cell-mediated immunity An experiment that used monoclonal antibodies that were specific for chick Ia (a chicken class II major histocompatibility complex antigen), and T and B-lymphocytes were observed to determine its effects on cellular infiltrates during the development of reovirus arthritis. Within the synovium collected, plasma cells and T-lymphocytes were the primary inflammatory cells present. During the acute-phase, CD8 cells were present in low numbers. The most activity was observed during the subacute phase with an increase in CD8 and CD4 lymphocytes. At this phase, clusters of IgM-positive, B-cells, T-cells, and plasma cells were also observed. During the chronic phase, a high amount of CD4 T- cells and a few IgM-positive B-cells were observed. Immunosuppression Infections of chickens with avian reovirus doesn't disrupt the functional capabilities of their T-cells, but induces suppressor macrophages that inhibit T-cell function. Diagnosis Although infection of avian reovirus is spread worldwide, it is rarely the sole cause of a disease. For chickens, the most common manifestation of the disease is joint/limb lameness. Confirming infection of avian reovirus can be detected through an ELISA test by using and observing the expression of σC and σB proteins. However, isolating and identifying reoviruses from tissue samples is very time-consuming. Isolation is most successfully attained through inoculation of material into chick embryo cultures or fertile chicken eggs. Inoculation of embryonic eggs through the yolk sac has shown that the virus usually kills the embryos within 5 or 6 days post inoculation. Analyzing the samples, the embryos appeared hemorrhagic and necrotic lesions on