Bovine babesiosis is a tick-borne, parasitic infection that causes significant morbidity and mortality in cattle. It is the most important arthropod-borne disease of cattle worldwide. The most prevalent species, Babesia bovis and B. bigemina, are found throughout most tropical and subtropical regions,. The economic losses from these two organisms can be considerable, particularly in developing countries. Although babesiosis can be controlled with vaccination and treated with antiparasitic drugs, the vaccines are live and have safety concerns, and many effective drugs have been withdrawn from the market due to safety or residue problems. B. bovis and B. bigemina were once endemic in the southern United States, and caused severe losses to the cattle industry. Although these organisms and their vectors were eradicated from the U.S. by 1943, reintroduction is a significant threat. Another important species, B. divergens, causes losses to farmers in parts of Europe and is a serious zoonotic threat to people who are immunocompromised.