Merozoite proteins fromBabesiasp. BQ1 (Lintan) as potential antigens for serodiagnosis by ELISA

Abstract

SUMMARYBabesiasp. BQ1 (Lintan) is aBabesiaisolated from sheep infested withHaemaphysalis qinghaiensisin China, and is closely related toB. motasibased on the 18S rRNA gene sequence. In the present study, an ELISA was developed with merozoite antigens ofBabesiasp. BQ1 (Lintan) (BQMA) purified fromin vitroculture. When the positive threshold was chosen as 30% of the antibodies rate, evaluated with 198 negative sera, the specificity was 95·5%. Except forBabesiasp. Tianzhu, there was no cross-reaction between BQMA and positive sera fromBabesiasp. BQ1 (Ningxian)-,Babesiasp. Hebei-,Babesiasp. Xinjiang-,Theileria luwenshuni-,T. uilenbergi-, orAnaplasma ovis-infected sheep, which are the dominant haemoparasites of small ruminants in China. Specific antibodies againstBabesiasp. BQ1 (Lintan) were produced 1 or 2 weeks post-infection and a high level of antibodies persisted for more than 8 months in experimentally infected sheep. This ELISA was tested on 974 sera collected from field-grazing sheep in 3 counties of Gansu province, northwestern China to evaluate the seroprevalence ofBabesiasp. BQ1 (Lintan) infection and the average positive rate was 66·84%. The feasibility of increasing the specificity of this BQMA-based ELISA, by using some BQMA antigens for serodiagnosis is discussed.