Comparison of cattle responses to mono-specific or combined inoculations with Babesia bigemina and Babesia bovis vaccine strains

Combined inoculation of cattle with vaccine strains of Babesia bigemina and Babesia bovis induced lower antibody titers to B. bigemina than to B. bovi s (previous study). Three groups of heifers were used to detect if the low antibody level was due to competition between Babesia species: individuals of G1 and G2 were inoculated with 10 million B. bigemina and B. bovis, resp ectively, and those of G3 with 10 million of each parasite. The prepatent p eriods, maximum parasitaemias and antibody titers (indirect immunofluoresce nt antibody test) were evaluated. The mean prepatent periods (days) for B. bigemina was of 5.6 (G1) and 5.2 (G3) and 7.0 (G2) and 6.7 (G3) for B. bovi s (P > 0.05, "t" test). No differences were found in the parasitaemias. The only difference was found in the antibody titers to B. bovis, that were lo wer (P < 0.05 "t" test) from week 7 onwards when B. bovis was used in combi nation. The biological significance of this difference is unclear.