Immunization of Foals with Equine Rotavirus A Vaccine Can Stabilize or Increase Rotavirus-Specific Neutralizing...

Despite a monovalent G3P[12] ('G3') vaccine being available for horses, equine rotavirus A (ERVA) is still the predominant infectious pathogen causing diarrhea in foals in the United States of America (U.S.). Previous research has shown that maternal neutralizing antibody (NAb) titers are too high and will interfere with the vaccination of foals at 30 and 45 days of age. We aimed to determine if it is possible to increase NAb titers in foals through vaccination before they are vulnerable to ERVA infection. We immunized two foals with the commercially available vaccine (G3) at solely three months of age and seven foals at both two and three months of age, respectively. Two mock foals were vaccinated with saline buffer in this study. The dams of these foals were not vaccinated during their gestation period. All pre-vaccination G3 and G14P[12] ('G14') NAb titers in this foal cohort were 256 or lower. Following vaccination, NAb titers in foals were increased up to 1024 against G3 and up to 512 against G14 viruses, respectively. Interestingly, ERVA NAb titers either increased or stabilized in immunized foals depending on the pre-vaccination NAb titer, which contrasts with unvaccinated foals showing a rapid decline in NAb titers over time.