Mehlhorn and Schein, 1998) (Phylum Apicomplexa) infection in Philippine horses correlated with parasite Apicomplexa) infection in Philippine horses correlated with parasite detection in blood smears detection in blood smears

Sera collected from 71 slaughtered and 33 racing horses were assayed for Sera collected from 71 slaughtered and 33 racing horses were assayed for Babesia spp. infection using immunochromatographic (ICT) assay. The ICT strips which were developed at the National Research Center for Protozoan Diseases (NRCPD), Obihiro University, Hokkaido, Japan contained a recombinant B. caballi 48-kDa rhoptry protein (rBc48) and a recombinant truncated B. equi merozoite antigen 2 (rEMA-2t) for the detection of anti-horse Babesia spp. antibodies. The 63 sero-positive blood samples consisted of 41(57.7%) and 22 (66.7%) cases in slaughtered and racing horses, respectively. Twelve sera (19.0%) reacted with both B. caballi and B. equi antigens, 45 sera (71.0%) reacted with rBc48 antigen only, and six sera (10.0%) were positive for B. equi antibodies only. Babesia caballi infection accounted for 90.5% cases. Infection with B. caballi and/or B. equi confi rmed in Giemsa-stained blood smears prepared from racing horse samples only revealed 22 (66.7%) seropositive cases. Paired pear or crescent-shaped merozoites (0.5-1.25 μm), characteristic of B. caballi were observed in 20 blood smears, while only two seropositive cases revealed the presence of both B. caballi and the Maltese cross or tetrad-shaped merozoites (0.62-0.95 μm) generally associated with Theileria sp. (B. equi) parasite. To our knowledge, this is the fi rst immunochromatographic assay of equine babesiosis in the Philippines validated by the detection of specifi c etiologic agent(s) in blood smears.