Babesia Taxa in Sika Deer in Hokkaido, Japan: Prevalence in Questing Ticks and Sympatric Grazing Cattle and Taxonomic Clarification

Cervids harbor several Babesia taxa, but their potential to infect cattle remains poorly understood. The present study detected Babesia taxa in wild sika deer in Hokkaido, Japan, and subsequently examined questing ticks collected from cattle pastures and sympatric grazing cattle for their presence. The initial screening of 285 sika deer blood DNA samples using a PCR assay targeting the 18S rRNA of Babesia spp., followed by sequencing, identified two previously reported Babesia taxa: one closely related to Babesia divergens and designated Babesia sp. Sika 1, and another unclassified Babesia taxon designated Babesia sp. Sika 2. A duplex PCR assay based on the obtained 18S rRNA sequences was then used to detect these two taxa in 285 sika deer, 671 questing ticks, and 767 cattle. Babesia sp. Sika 1 was detected in 86/285 (30.2%) deer and 7/367 (1.9%) Ixodes persulcatus ticks, whereas Babesia sp. Sika 2 was detected in 4/285 (1.4%) deer but not in the examined ticks. Neither taxon was detected in any cattle samples. Phylogenetic analyses placed Babesia sp. Sika 1 in a distinct lineage from B. divergens, supporting its recognition as a distinct Babesia taxon. Similarly, Babesia sp. Sika 2 formed a distinct phylogenetic clade in the 18S rRNA analysis. Despite opportunities for exposure through shared pasture environments and I. persulcatus feeding on both hosts, neither taxon was detected in the examined cattle. Further studies are now essential to confirm and extend our findings regarding the taxonomic status and host associations of Babesia sp. Sika 1 and Babesia sp. Sika 2.