[The effect of different strains Babesia bovis (Babes, 1888) on tick of Boophilus microplus (Canestrini, 1887)].

Two samples (modified and no-modified) of Babesia bovis, were used to evaluate the effect on engorged females of Boophilus microplus Babesia spp - free. For so much, were used three holstein breed bovine, males with 6 months of age, (BH1, BH2 and BH3), coming of the Plateau of Itatiaia, Rio de Janeiro, Brazil. Each calf was infested with 0.2g of B. microplus larvae Babesia spp- free, for 10 consecutive days. They were inoculated in the calves BH1 and BH2, modified and no modified sample, respectively. After natural fall of adults ticks from the vertebrate host, 100 engorged females of each host (BH1, BH2 and BH3) were incubated in BOD, with superior Relative Humidity up 80%, Temperature of 28 degrees C, were appraised daily until the 12th day post incubation (dpi.). In the group of the engorged females obtained of calf BH1, infection of ticks was not observed, to the haemolymph exam and oviposture. The sporokinets absence in these samples was related with the successive passages in splenectomized calves and the criopreservation of the sample. In engorged females from BH2 it was observed rates of infection of 100% and 82% of mortality in 7th dpi. and 100% until 12nd dpi., as the oviposture, 70% did not make oviposition and 30% made it until 7th dpi.