Correlation between neutralizing antibody titre and protection from tenosynovitis in avian reovirus infections.

The relationship between neutralizing antibody titre and protection from tenosynovitis caused by avian reovirus infection was examined using actively or passively immunized chickens. Actively immunized groups which developed geometric mean neutralizing antibody titres (GMT) of 1:238 or higher exhibited good protection (more than 71%) against challenge with avian reovirus strain 58-132 via the footpad. On the other hand, 87% of passively immunized chicks, which received chicken serum hyperimmune to avian reovirus in the yolk sac and possessed GMT of 1:100 upon hatching, were protected against oral challenge. Given the age-related resistance to reoviral tenosynovitis and the half-life of maternal antibody, chicks should ideally have 1:1600 or higher maternal antibody titre at the time of hatching to be protected against oral infection until 3 weeks of age.