Transplacental transmission of Theileria orientalis occurs at a low rate in field-affected cattle: infection in utero does not appear to be a major cause of abortion.

These findings indicate transplacental transmission of T. orientalis appears to play only a minor role in persistence of T. orientalis infection in the field; however calves are highly susceptible to developing high level T. orientalis infections at 4-8 weeks of age regardless of whether maternal antibodies are present post-partum.