Passive immunity in foals born from mares vaccinated against Theileira equi and Streptococcus equi subspecies equi

Abstract

The aims of this study were: 1) determine total specific IgG and subisotypes in serum and colostrum of pregnant mares vaccinated against Theileria equi and Streptococcus equi subspecies equi; 2) determine total specific IgG and subisotypes in foals born from these mares. In mares, the highest total serum IgG value for T. equi was at 335 days of gestation declining 30 days postpartum, while for S. equi was at 328 days of gestation remaining high up to 30 days postpartum. Transfer of passive immunity against both antigens was observed with specific IgG values in colostrum and foals’ serum proportional to mares’ values. The most detected specific IgG subisotypes were IgG3/5 and IgG4/7 for both antigens. Foals born from mares immunized with T. equi kept maternal IgG values until 2 months of age, while those born from mares immunized with S. equi kept maternal IgG values until 3-4 months of age. These results suggest that foals should be vaccinated after this period.