Characterization and comparison of merozoite antigens of different Babesia canis isolates by serological and immunological investigations.

Merozoites of four Babesia canis isolates from Hungary, France, Africa, and Egypt were purified. Antigens were compared in an enzyme-linked immunosorbent assay (ELISA) and by immunoblotting. In the ELISA, antigen from the highly pathogenic isolate from Hungary showed the highest sensitivity for homologous and heterologous immune sera. This was confirmed by immunoblotting. Protein bands of the Hungarian isolate were strongly recognized by all B. canis immune sera, whereas the antigens from the other isolates showed only weak reactions with homologous and heterologous immune sera. Significant was a protein band of about 12 kDa appearing in all pathogenic isolates from Hungary, France, and South Africa but not in the apathogenic Egyptian isolate. This protein band may determine the virulence. For serological tests, the B. canis isolate from Hungary seems to be the one most suitable for detection of even mild infections.