Eimeria bovis in cattle: colostral transfer of antibodies and immune response to experimental infections

Abstract

IgM, IgG₁, and IgG₂ antibodies toEimeria bovis first-generation merozoite antigens were determined by enzyme-linked immunosorbent assay and Western blotting in naturally infected cows and in their offspring before and after the uptake of colostrum. In addition, calves were examined following experimental primary and challenge infections. Neonate calves received maternal antibodies via colostrum. All isotypes determined were transmitted, but only IgG₁ was concentrated in the colostrum and it occurred at significantly increased levels in sera from the calves as compared with those from the respective dams. Recognition patterns (Western blotting) displayed by related maternal serum and colostrum and those shown by calves that had ingested colostrum were very similar, but marked variations occurred between individual pairs. Experimental infection of 15-week-old calves with 0.7×10⁵ oocysts caused strong protective immunity against a challenge with 1×10⁵ oocysts. In contrast, animals that had undergone a weak intercurrent infection were not protected. Experimental infections induced a considerable increase in IgG₁ and IgG₂ antibody levels, whereas IgM values increased only slightly. The spectrum of merozoite antigens recognized by the sera increased markedly after experimental infection, although high individual variations were found in the calves. However, there was no correlation between the levels of any specific antibody or the recognition patterns and the status of immunity to a severe challenge.