Seroprevalence of Newcastle Disease among Unvaccinated Village Chickens in Coimbatore District, Tamil Nadu, India

Newcastle disease causes enormous economic losses to the poultry industry. Despite vaccination efforts, Newcastle Disease (ND) remains endemic in many developing countries, causing major economic losses and impacting food security. A serological survey for antibodies against Newcastle Disease virus (NDV) was conducted in 294 unvaccinated village chickens in Coimbatore District, Tamil Nadu, India. Sampling was conducted between March and August 2025. All chickens were confirmed to be unvaccinated based on interviews with the farmers and veterinary records. This study aimed to assess the seroprevalence of NDV antibodies in village chickens and identify the factors influencing their susceptibility to NDV infection. The haemagglutination inhibition (HI) test was used to detect NDV antibodies in the village chickens. The lowest seroprevalence was detected in Valparai at 32%, and the highest in Cambotore South at 62%. Only the Mettupalayam village chickens had a protective antibody titer above the recommended minimum protective antibody titer of ≥ 3(log2) against NDV. These research findings indicate continued NDV exposure among unvaccinated village chickens, underscoring the urgent need for vaccine deployment and improved poultry health management before the virus reaches large commercial farms. Strengthening active surveillance and laboratory diagnostic capacity will be crucial for sustainable NDV control in Coimbatore District. Although molecular confirmation was beyond the scope of the current study, future work should employ RT-PCR and sequencing of the F gene cleavage site to identify circulating NDV genotypes. A longitudinal seromonitoring study is also planned to assess antibody persistence and seasonal variation.