Epidemiological survey of a cervine Theileria in wild deer, questing ticks, and cattle in Hokkaido, Japan

Species of Theileria are tick-borne hemoprotozoan parasites of ruminants that can cause severe clinical disease. In this study, blood samples were obtained from 91 wild sika deer in various districts in Hokkaido, Japan. Samples were tested using a PCR assay designed to amplify a full-length major piroplasm surface protein (MPSP) gene of a cervine Theileria species, designated as Theileria sp. (sika 1). The amplicons of 57 out of 89 PCR-positive samples were cloned and sequenced. The sequences shared 99.1%-100% identity scores, indicating the MPSP gene of Theileria sp. (sika 1) is highly conserved. Next, a Theileria sp. (sika 1)-specific PCR assay was developed based on the newly-generated MPSP gene sequences and used to screen DNA samples from 671 questing ticks, collected from cattle pastures where wild sika deer are often observed, in Hamanaka, Shibecha, Shikaoi, Otofuke, Taiki, and Shin-Hidaka districts of Hokkaido. Ixodes persulcatus and Haemaphysalis japonica were infected with Theileria sp. (sika 1), while Ixodes ovatus and Haemaphysalis megaspinosa were negative. Furthermore, blood DNA samples collected from 767 cattle, grazing on the same pastures where the ticks had been collected, were negative for Theileria sp. (sika 1), using the same PCR assay. The MPSP gene from Theileria sp. (sika 1)-positive ticks was sequenced. The Theileria sp. (sika 1) MPSP gene sequences from ticks shared 99.1%-100% identity scores with those from the wild sika deer. In a phylogenetic analysis, Theileria sp. (sika 1) MPSP gene sequences from both deer and ticks clustered together and formed a monophyletic clade. Our findings infer that I. persulcatus and H. japonica are potential vectors for the transmission of Theileria sp. (sika 1) to sika deer but not cattle, though I. persulcatus and H. japonica are known to infest both cattle and wild sika deer in Hokkaido.