Age- and agro-climatic zone-specific variations in post-vaccinal antibody responses to FMD vaccination in bovine populations: a longitudinal study from Karnataka, India.

This longitudinal study examined variations in post-vaccination antibody response to Foot-and-Mouth Disease (FMD) vaccination in bovines across different age groups and agro-climatic zones in Karnataka, India. A total of 374 serum samples were collected from 28 villages across nine agroclimatic zones, targeting pre- and post-vaccination titers for FMD virus serotypes O, A, and Asia-1. Analysis via single-dilution liquid-phase blocking ELISA revealed significant findings: pre-vaccination immune proportions were below the herd immunity threshold (< 80%) for serotypes O and Asia-1 but exceeded it for serotype A. Younger bovines (< 24 months) displayed notably lower antibody titers (log₁₀1.67-1.99) compared to older cattle (> 24 months; log₁₀2.14-2.44), highlighting the age-dependent vaccine response variability. Agroclimatic disparities were evident, with regions like the Coastal and Central Dry Zones failing to achieve protective titers (log₁₀<1.8) even post-vaccination, whereas zones like the Eastern Dry Zone demonstrated marked improvements. Post-vaccination seromonitoring showed an overall increase in immune proportions for all serotypes, yet younger cattle and certain agroclimatic zones remained suboptimal. These findings emphasize the importance of region-specific vaccination strategies and the need for tailored booster protocols to enhance immunity in younger bovines. The study underscores the utility of seromonitoring in optimizing FMD control programs by addressing age and agro-climatic disparities in immune responses.