Expression of Equi Merozoite Antigen 2 during Development of Babesia equiin the Midgut and Salivary Gland of the Vector Tick Boophilus microplus

ABSTRACTEqui merozoite antigens 1 and 2 (EMA-1 and EMA-2) are Babesia equiproteins expressed on the parasite surface during infection in horses and are orthologues of proteins in Theileriaspp., which are also tick-transmitted protozoal pathogens. We determined in this study whether EMA-1 and EMA-2 were expressed within the vector tick Boophilus microplus. B. equitransitions through multiple, morphologically distinct stages, including sexual stages, and these transitions culminate in the formation of infectious sporozoites in the tick salivary gland. EMA-2-positive B. equistages in the midgut lumen and midgut epithelial cells of Boophilus microplusnymphs were identified by reactivity with monoclonal antibody 36/253.21. This monoclonal antibody also recognized B. equiin salivary glands of adult Boophilus microplus. In addition, quantification of B. equiin the mammalian host and vector tick indicated that the duration of tick feeding and parasitemia levels affected the percentage of nymphs that contained morphologically distinct B. equiorganisms in the midgut. In contrast, there was no conclusive evidence that B. equiEMA-1 was expressed in either the Boophilus microplusmidgut or salivary gland when monoclonal antibody 36/18.57 was used. The expression of B. equiEMA-2 in Boophilus microplusprovides a marker for detecting the various development stages and facilitates the identification of novel stage-specific Babesiaproteins for testing transmission-blocking immunity.