Detection and molecular characterization of Babesia caballi and Theileria equi isolates from endemic areas of Brazil

Blood samples were collected from 487 adult horses, including 83 pregnant mares, at a slaughterhouse located in Araguari, Minas Gerais State, Brazil. For each blood sample, the packed cell volume (PCV) was determined, and Giemsa-stained smears were microscopically examined for the presence of hemoparasites. The plasma was examined by the indirect fluorescent antibody test for detection of antibodies against Babesia caballi and Theileria equi. In addition, DNA was extracted and analyzed by a multiplex real-time polymerase chain reaction (PCR), specific for B. caballi and T. equi. Products of PCR were sequenced and compared with each other and with known sequences. The serological results showed a total prevalence of 91.0% for T. equi and 83.0% for B. caballi, while by PCR, prevalences of 59.7% for T. equi and 12.5% for B. caballi were observed. However, no correlations were seen between positivity (neither by serology nor by PCR) and PCV values. As expected, the microscopic examination of blood smears showed low sensitivity in detecting the infections when compared to the PCR. Only 35 out of 570 blood smears were positive, with parasitemias below 0.1%. No congenital transmission was detectable. As far as sequencing is concerned, no differences were seen among the isolates of each species nor among them and known sequences available. These results confirm, by molecular methods, the high prevalence rates of T. equi and B. caballi infections in carrier horses in Brazil. However, no diversity was observed among the isolates within the studied regions.