Evaluation of a cloned Babesia bovis organism as a live immunogen.

A Babesia bovis isolate was cloned by in vitro cultivation and compared to the original cultured isolate for pathogenicity by animal inoculation. Four yearling heifers were inoculated with cloned material and 4 with the original culture. The four animals which received the cloned Babesia showed comparatively minor hematologic changes and no clinical signs. One animal died in the group that received uncloned Babesia and the mean temperature increase and mean reduction in packed cell volume (PCV) was greater in that group. The four animals receiving the cloned material were challenged 100 days following initial inoculation. All of the animals were totally immune with no significant change in temperature or decrease in PCV, whereas control (previously non-inoculated) animals developed significant (P less than 0.001) increases in temperature and severe anemia. The cloned organism appears to be a candidate live immunogen for use in endemic areas to induce protection against bovine babesiosis.