Simultaneous immunization of cattle with foot-and-mouth disease (FMD) and live anthrax vaccines do not interfere with FMD booster responses

Foot-and-mouth disease (FMD) vaccination in Argentina is compulsory for most of the cattle population and conducted by certified veterinarians. This organized campaign may facilitate the controlled application of other vaccines against endemic diseases, provided immune responses against FMD are not hindered. There is no published information on the interference of immunity against FMD vaccines when applied together with a live bacterial vaccine. In this study we evaluated if the simultaneous application of a Bacillus anthracis live vaccine with a commercial tetravalent oil-based FMD vaccine (FMD-vac) used in Argentina, modifies the antibody booster responses against FMD virus (FMDV) in cattle. Two groups of 16 heifers with comparable liquid phase blocking ELISA (LPBE) titers were immunized with the FMD-vac alone or simultaneously with a commercial attenuated bovine anthrax Sterne strain vaccine (ABV). Serum samples were obtained at 0, 25, 60 and 90 days post vaccination (dpv) and specific antibodies against two FMDV vaccine strains were assessed by LPBE, avidity and IgG-isotype ELISAs. Bovines immunized with FMD-vac or FMDV-V + ABV responded with a boost in the LPBE antibody titers and avidity at 25 dpv, and remained within similar levels up to the end of the study. Animals vaccinated with FMD-vac + ABV had significantly higher LPBE titers at 25 dpv, compared to those immunized with FMD-vac alone; which was due to an increase in IgG2 titers. Overall, antibody titers elicited in both groups were similar and followed comparable kinetics over time. We conclude that the simultaneous application of a live anthrax vaccine with the current FMD tetravalent vaccine used in Argentina in cattle previously immunized against FMD, did not counteract the serological response induced by FMD vaccination.