Genetic diversity of Theileria orientalis in tick vectors detected in Hokkaido and Okinawa, Japan

Abstract

In the present study, we investigated the possible tick vectors that can transmit Theileria orientalis in eastern Hokkaido, Japan. Questing ticks collected from three different districts, Taiki, Otofuke, and Shin-Hidaka, of Hokkaido included Ixodes persulcatus, Haemaphysalis megaspinosa, Haemaphysalis douglasi, and Ixodes ovatus, while all the ticks collected from Yonaguni island of Okinawa were identified as Haemaphysalis longicornis. When the ticks were screened by polymerase chain reaction (PCR) for T. orientalis, the parasite was commonly detected among all tick species. Genotype-specific PCR assays revealed that all tick species in Hokkaido were predominantly detected with type 2, while ticks collected from Okinawa (H. longicornis) were predominantly detected with type 1. Consistent with the genetic diversity of T. orientalis in ticks, genotyping PCR assays from cattle grazed in the same Hokkaido sampling locations identified type 2 as the most prevalent genotype. This study provides the first identification of I. persulcatus, H. megaspinosa, H. douglasi, and I. ovatus as possible tick vectors of T. orientalis, and finds that the variety of vectors apparently capable of transmitting T. orientalis is wider in Japan than expected. The authors suggest that tick control strategies should be modified in Hokkaido based on the seasonal activities of ticks identified in the present study.