Field Evidence of Fasciola hepatica-Mediated Modulation of Antibody Responses to Foot-and-Mouth Disease Vaccination in Buffaloes

Abstract

We previously showed that experimental Fasciola hepatica infection reduces antibody avidity in cattle vaccinated against foot-and-mouth disease virus (FMDV), despite stable total FMDV-specific antibody levels. Here, we assessed the humoral response of water buffaloes (Bubalus bubalis), a species relevant to FMDV epidemiology. These animals were naturally infected with F. hepatica under field conditions. Two herds (n = 50 each) were selected based on fecal egg detection and anti-F. hepatica seropositivity. All animals had received two doses of FMDV vaccine, with the last dose administered 264 days before sampling. Serum samples were analyzed for virus-neutralizing titers (VNT), total anti-FMDV levels measured by Liquid-Phase Blocking ELISA (LPBE), IgG levels, and IgG avidity against the A24/Cruzeiro vaccine strain. Infected animals showed significantly lower VNT, LPBE titers, IgG levels, and avidity indexes compared to non-infected counterparts. These findings indicate that F. hepatica infection can impair the humoral response to FMD vaccination and highlight the need to monitor immune status in vaccinated buffaloes in endemic areas.