Babesia equi (Laveran 1901) 1. Development in horses and in lymphocyte culture.

The vertebrate development of Babesia equi from infected Hyalomma marginatum in Morocco was investigated in vitro and in vivo. It was demonstrated that the sporozoites of B. equi initiate a phase of exo-erythrocytic schizogony in lymphocytes both in vitro and in vivo. On the other hand, sporozoites did not invade erythrocytes in vitro. The complete vertebrate life cycle of B. equi was simulated in vitro, from the invasion of lymphocytes by sporozoites, to the development of macro- and microschizonts, the invasion of erythrocytes by merozoites, and the subsequent intra-erythrocytic schizogony. In the equine host, macro- and microschizonts were detected in lymph node biopsies during the febrile phase on days 12 to 14 after application of ticks. As a result, the taxonomic position of B. equi appears to be uncertain.