Analysis of the genetic diversity of Babesia bovis msa-1 in Thailand using type-specificpolymerase chain reaction

摘要

Babesia bovis, a tick-bome hemoprotozoan parasite, causes fatal bovine babesiosis in cattle. Merozoite surface antigens, encoded by msa genes, of B. bovis play an important role in the initial attachment of the merozoite to host erythrocytes. In the present study, B. 6ov/s-positive blood DNA samples (n = 162) sourced from cattle in Thailand were analyzed using type-specific polymerase chain reaction (PCR) assays targeting nine Asian msa-1 genotypes (genotypes C and AS1-AS8). All nine msa-1 genotypeswere detected in Thai cattle, and at least one msa-1 genotype was detected in 154 of the 162 samples. The most common genotype was AS7 (n = 139), followed by AS5 (n = 61), AS1 (n = 37), AS8 (n = 32), C (n = 11), AS4 (n = 8), AS3 (n = 5), AS6 (n = 2), andAS2 (n = 1). Co-infection with parasites of different genotypes was also commonly detected, and with 90 (58.4%) of the 154 PCR-positive DNA samples showing infection with more than one genotype. Overall, the detected genetic diversity of msa-1 from B. bovis was much higher than that previously determined in Thailand. These findings warrant further investigation to determine the nature of antigenic variation between the different B. bovis genotypes detected in the cattle population of Thailand.