A Survey of Spotted Fever Group Rickettsia and Anaplasmataceae Bacteria in Questing Ticks in Hokkaido, Japan

Background: Tick-borne diseases caused by spotted fever group (SFG) Rickettsia and members of the family Anaplasmataceae are important public health concerns. Given that previous studies on SFG in Hokkaido, the northernmost prefecture of Japan, have been limited by small sample sizes or limited to specific pathogens or tick species, the epidemiology of tick-borne bacteria remains unclear. This study investigated the prevalence of SFG Rickettsia and Anaplasmataceae bacteria in multiple tick species in Hokkaido. Methods: DNA was extracted from 1,115 questing ticks representing six species (548 Ixodes ovatus , 368 Ixodes persulcatus , 95 Haemaphysalis concinna , 74 Haemaphysalis japonica , 28 Haemaphysalis megaspinosa , and 2 Haemaphysalis longicornis ) collected from six districts in Hokkaido. Samples were screened using PCR assays targeting the gltA gene of SFG Rickettsia species and the groEL gene of Anaplasmataceae. Amplicons were sequenced for species identification. Results: SFG Rickettsia DNA was found only in I. persulcatus (48.9%, 180/368), including R. helvetica (32.1%) and Candidatus R. tarasevichiae (16.8%). Anaplasmataceae DNA was detected in 3.9% (44/1,115) of ticks, including I. persulcatus , I. ovatus , H. japonica , and H. megaspinosa . In I. persulcatus , Ehrlichia muris , Candidatus Neoehrlichia mikurensis, and Anaplasma phagocytophilum were detected in 4.6%, 3.3%, and 0.3%, respectively. Ehrlichia japonica was found in I. ovatus (0.9%), while unclassified Ehrlichia spp. were detected in H. japonica (1.4%) and H. megaspinosa (3.6%). Seventeen I. persulcatus (4.6%) carried both SFG Rickettsia and Anaplasmataceae. Conclusions: The findings showed that questing ticks in Hokkaido harbor zoonotic bacteria. While I. persulcatus appears to be the principal vector, the detection of pathogens in I. ovatus , H. japonica , and H. megaspinosa suggests the potential for additional vectors in the region. These findings underscore the importance of continuous surveillance and heightened clinical awareness of tick-borne diseases in northern Japan.