Epidemiological survey of Babesia divergens Asia lineage in wild sika deer (Cervus nippon) by using direct PCR, in Japan.

Babesia divergens is the major causal agent of zoonotic human babesiosis in Europe. In Japan, a parasite genetically closely related to the European B. divergens, B. divergens Asia lineage, was detected in wild sika deer (Cervus nippon) in our previous study. We therefore conducted large epidemiological survey by combining lineage specific PCR system and blood direct PCR. The infection rate of the Asia lineage was 6.6% (116/1747) throughout the country, where Hokkaido (45%), Nagano (17%), Iwate (12%), Gunma (11%) and Yamanashi (11%) were highly enzootic (>10%) among 30 prefectures examined. European B. divergens was not detected. A Geographical Information System (GIS) map revealed PCR-positive deer densely populated in mountain areas including Japanese Alps in eastern Honshu, and Hokkaido. These areas are strikingly overlapped with the major habitats of Ixodes persulcatus, a principal tick vector for the lineage. Other tick species may be involved in the enzootic cycle in south including Miyazaki, Kagoshima and Shimane Prefectures, where positive sika deer were sporadically detected while I. persulcatus are scarce. Emerging human babesiosis is occasionally caused by healthy blood donor who unaware of tick bite and Babesia infection. It is urgently needed to investigate whether infection in human is occurred in Japan.