Babesia bovis: infectivity of an attenuated strain of Brazilian origin for the tick vector, Boophilus microplus.

In order to verify the infectivity and transovarian transmission of one strain of Babesia bovis of Brazilian origin, attenuated by repeated passages in splenectomized calves to the biological tick vector, Boophilus microplus, an inoculation of that strain was performed in hemoparasite-free calves infested with hemoparasite-free ticks. Subsequently, engorged female ticks were collected to examine hemolymph and progeny for presence of developing stages of Babesia bovis. Using an optical microscope, intrahemocytic merozoites were observed in female hemolymph on the second and fourth days, respectively, after ticks dropped from calves. By histological observation of F1 larvae, after more than 24 h of adherence on calves, sporokinetes and small merozoites were present in the samples of hemolymph. These results confirmed the maintenance of infectivity by the vaccine strain attenuated after 26 passages for tick Boophilus microplus.