BABESIOSIS - NEW INSIGHTS FROM PHYLOGENETIC ANALYSIS

Piroplasms of the genus Babesia, along with their relatives to the The ileridae, comprise a genetically and antigenically diverse group of ti ck-transmitted intraerythrocytic pathogens that together have consider able veterinary, medical, and economic importance. Since the first des cription of a human case of babesiosis in 1957, this zoonotic infectio n has now attained a worldwide distribution. In the northeastern and u pper midwestern United States, the transmission cycle of Babesia micro ti overlaps that of another well-known zoonotic agent, Borrelia burgdo rferi, the causative agent of Lyme disease. Phylogenetic analysis of B abesia and Babesia-like piroplasms from human and animal sources has s hown that many of the small Babesia spp., including B. microti, B. equ i, B. gibsoni, and a recently described piroplasm infectious for human s known as WAI, may be phylogenetically related to Theileria. Implicat ions of this observation may include the possible existence of an exoe rythrocytic stage of parasite development and attendant features of ch ronicity, immune suppression, and perhaps lymphoproliferation. In this review, we provide a brief summary of recent developments in the stud y of Babesia and related piroplasms and speculate on the ramifications of chronic babesial infection in humans.