EVALUATION OF DIFFERENT TURKEY RHINOTRACHEITIS VIRUSES USED AS ANTIGENS FOR SEROLOGICAL TESTING FOLLOWING LIVE VACCINATION AND CHALLENGE

Two enzyme-linked immunosorbent assays (ELISA) developed in the authors' laboratory for turkey rhinotracheitis serological testing, a commercial ELISA kit, and two virus-neutralization (VN) assays were compared with respect to the efficiency of these assays for serological monitoring in specific-pathogen-free (SPF) turkeys inoculated with four pathogenic isolates of turkey rhinotracheitis virus, with or without previous live vaccination. Both the live vaccine and the different isolates of virus were shown to induce antibody rises, the detectability of which varied depending on the ELISA or VN assay used for serological testing. The results show that 3 weeks after vaccination with an attenuated strain, the choice of an inadequate antigen for serological testing may be the cause of an apparent lack of immunogenicity of the vaccine, and that 2 weeks after challenge, such a choice in ELISA can also hinder the early diagnosis of a TRT virus infection in both vaccinated and unvaccinated turkeys.