Reovirus‐induced tenosynovitis in chickens the influence of age at infection

Groups of specific pathogen-free (SPF) light hybrid chickens were infected with an arthrotropic reovirus at 1 day old, or at 2, 4, 6 or 9 weeks of age. In each group, approximately 20 were infected orally and 6 via the footpad. For each age group clinical signs of tenosynovitis, gross and microscopic lesions in the legs, virus excretion in the faeces, virus persistence in the joints, and precipitin response to reovirus were observed over a period of 9 weeks post infection (p.i.). For both routes of infection an age-limited susceptibility was shown, the most serious effects, both in numbers of affected birds and severity of gross lesions including tendon rupture, being seen in the youngest group. Gross lesions were rarely seen after oral infection of 6- and 9-week-old chickens. Footpad inoculation of virus had a more severe effect overall, and extended the age susceptibility, mild leg swellings being seen in some birds infected at 6 and 9 weeks of age. After oral infection, higher virus titres in the faeces and a more prolonged persistence in the gut and hock joint were recorded in chicks infected at 1 day old compared with the other age groups. Also, compared with the older groups, a delayed precipitin response was found in those infected at 1 day old. Footpad inoculation provoked earlier virus replication in the gut and a more rapid precipitin response.