Theileria-free grazing of dairy heifers on grassland in Kyushu, Japan where T. orientalis was epidemic before a 7-year vacancy

This study aimed to produce a Theileria-free grazing system for Holstein heifers reared on a dairy farm in the Hita area, Kyushu, Japan. In the grazing area, spreading of T. orientalis infection was confirmed in 2009. To eradicate the T. orientalis infection, four measures were conducted: 1) 7-year deferred grazing; 2) grazing only T. orientalis-uninfected heifers; 3) anemia check by red blood cell parameters at least once per month; and 4) protecting heifers from blood-sucking T. orientalis-infected ticks. Grazing was restarted in 2017 in the same area and continued to 2021. During last 2 years of pasturing (2020–2021) all of the 129 heifers were confirmed to be T. orientalis-free. In summary, it is possible to establish a T. orientalis-free grazing system by conducting appropriate measures.