Reovirus-induced tenosynovitis in chickens: the effect of breed

The effect of breed of chicken on infection with an arthrotropic avian reovirus (strain R2) was studied by oral or footpad inoculation of day-old chicks of the SPF light-hybrid, commercial White Leghorn egg-layer, and commercial Ross I broiler breeds, observed to 12 weeks of age. Although most inoculated birds of all three breeds developed swelling of one or both legs below the hock joint at 3 to 4 weeks of age, gross lesions of tenosynovitis became progressively more severe and extended above the joints only in broilers, whereas in most orally-infected SPF and commercial light chickens gross lesions were intermittently severe and regressed with time. Cloacal virus shedding continued up to 2 weeks in the lighter breeds and 3 weeks after infection in broilers. From a small proportion of infected chickens, reovirus was also recovered from heart, pancreas and caecal tonsils. In all breeds, the tissue in which virus persisted longest was the hock joint/tendon. There was a poor correlation between isolation of virus and the presence of gross lesions in chickens of 12 weeks of age, especially in broilers. Virus-neutralization tests demonstrated that seroconversion in the lighter breeds occurred mainly at 3 weeks, and in broilers at 4 weeks after infection. In all three breeds the footpad infection resulted in poorer growth than in the control and oral-infection groups. Oral infection had no apparent effect on growth rate. The greater susceptibility of broilers to reovirus infection is discussed..