The Babesia divergens Asia Lineage Is Maintained through Enzootic Cycles between Ixodes persulcatus and Sika Deer in Hokkaido, Japan.

Parasites of the Asia lineage, which are closely related to in Europe and sp. strain MO1 in the United States, were recently reported in sika deer () in eastern Japan. To identify the tick vector(s) for this parasite, we conducted a field survey in Hokkaido, Japan, where the infection rate in sika deer is the highest in the country. A specific PCR system which detects and discriminates between lineages within and between those lineages and showed that (11/822), but not sympatric (0/595) or sp. (0/163) ticks, carried Asia lineage. Genomic DNA was archived from salivary glands of partially engorged females and three isolates of Asia lineage were newly described. The 18S rRNA gene sequence of the isolates formed the Asia lineage cluster with those previously described in sika deer isolates. One salivary gland also contained parasites of U.S. lineage, which were subsequently isolated in a hamster (strain Etb5) was also detected in one tick. The 18S rRNA sequence of Etb5 was 99.7% identical to that of (AY046575) and was phylogenetically positioned in a taxon composed of isolates from Europe, China, and Russia. The geographical distribution of is consistent with that of in sika deer in Japan. These results suggest that is a principal vector for in Japan and Eurasia, where is predominantly distributed. The Asia lineage of parasites closely related to in Europe and sp. MO1 in the United States was recently reported in in eastern Japan. In this study, specific PCR for the Asia lineage identified 11 positives in 822 host-seeking ticks, a principal vector for many tick-borne disease agents. Gene sequences of three isolates obtained from DNA in salivary glands of female ticks were identical to each other and to those in We also demonstrate the coinfection of Asia lineage with U.S. lineage in a tick salivary gland and, furthermore, isolated the latter in a hamster. These results suggest that is the principal vector for as well as for , and both parasites may be occasionally cotransmitted by This report will be important for public health, since infection may occur through transfusion.