Transplacental Transmission of Theileria equi Is Not a Common Cause of Abortions and Infection of Foals in Israel.

Although the main route of transmission of Theileria equi is through tick feeding, transplacental transmission is also possible and may lead to abortion, or to the birth of a sick or carrier foal. The aim of this study was to evaluate the role of T. equi as a cause of abortions in Israel and the risk of foals being infected at a young age. Eight aborting mares were serologically evaluated for exposure to T. equi via the immunofluorescence antibody test (IFAT) and their aborted fetuses were evaluated using PCR and qPCR. In addition, five mares and their foals (aged 4-6 months) from a highly endemic farm were tested for T. equi infection using IFAT, PCR and qPCR. Five of the eight aborting mares were seropositive for T. equi; however, none of the aborted fetuses was infected. All five mares from the endemic farm were subclinically infected with T. equi. Of their five foals, one was infected, with relatively high parasitemia and different parasite genotype than its dam's, suggesting another source of infection. The results of this study suggest that transplacental transmission of T. equi is not common and does not appear to be a prominent cause of abortion in chronically infected mares.