Babesia ovis, an intraerythrocytic protozoan parasite transmitted by ticks, causes severe
infections in sheep in tropical and subtropical regions of the world. Parasite-specific immunoreactive
proteins have been used as
antigen in the serological diagnosis of
babesiosis. There is no study about determination of B. ovis-specific
proteins in sheep. This study was planned to determine the immunoreactive
proteins of B. ovis. In this study, two splenectomized lambs, and twelve seropositive sheep and five seronegative lambs for anti-B. ovis
antibodies were used as materials. Infected blood samples at 5% of
parasitemia from the two splenectomized lambs experimentally infected with a virulent B. ovis field strain were analyzed for B. ovis-specific
proteins by
sodium dodecyl sulfate-
polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting (WB). B. ovis-specific five major
proteins were recognized by anti-B. ovis serum but not by healthy sheep serum. They were of approximate molecular weights 154, 109, 77, 58, and 38 kDa. As the control samples,
protein profiles of the blood extracts of two lambs before
splenectomy operation were also blotted with the
immune sera, but none of the five
proteins was detected. These
proteins were also immunoblotted with heterologous positive and negative sheep sera. All of twelve positive sera recognized the 109 kDa
protein with 100 percent sensitivity. The 77 kDa
protein reacted in 11 of 12 sera (91.6%). The sensitivities of the other 3
proteins ranged between 83.3% and 25%. The five
protein bands immunoblotted with sera of the 5 negative lambs did not give any positive reaction. The results of this study revealed the presence of
proteins recognized by the serum
antibodies of experimentally and naturally infected sheep with B. ovis. Additional studies on the purification of these
proteins and on subsequently their utilization in a serodiagnostic method are required to improve the serological diagnosis of ovine
babesiosis.