Determination of probable vectors for human babesiosis as a emerging infectious disease

微巴贝斯虫是啮齿动物的红细胞内寄生虫，通过蜱传播。日本第一例人间病例于1999年在神户市报告。经证实，该患者是通过从无症状的献血者那里输血而感染的。流行病学研究表明，日本有两种基因不同的微孢子虫，即大津型和神户型。由于目前对日本微蠓病媒的研究较少，本研究旨在确定日本微蠓病媒的可能性。进行了以下三个实验。蜱类中微蠓的直接检测。从遗传学和细胞学上在兵库县六高山和淡河岛采集的卵形伊蚊唾液腺中发现了微小的Otsu型。然而，尚未在蜱虫中检测到神户型微蜱。另一方面，在北海道的过弯伊蚊和长野县的卵形伊蚊中分别新发现了美国型和长野型微型伊蚊。实验感染在未取食的卵蜱的唾液腺中，微蜱在颗粒状腺泡细胞中处于成孢子期，在取食实验寄主2 d后发育为孢子子期。结果表明，卵形夜蛾参与了日本啮齿动物体内寄生虫的维持。在青森县、岛根县、长崎县和鹿儿岛县等地发现了神户型微型小蠊的分布。在长野县也发现了感染长野型微孢子虫的啮齿动物。已知日本有四种微孢子虫基因型（大津、神户、长野和US）。

Babesia microti is an intraerythlocytic parasite of rodents, which is transmitted by ticks. The first human case in Japan was reported in 1999 from Kobe city. It was proved that the patient was infected through a blood transfusion from an asymptomatic donor. Epidemiological studies revealed that there are two genetically different types of B.microti, Otsu and Kobe type, in Japan. As there are few studies on the vector of Japanese B.microti, the present study was designed to determine the probable vector of the parasite. The following three experiments were conducted.1. Direct detection of B.microti from ticksB.microti Otsu type was found genetically and cytologically in salivary glands of Ixodes ovatus collected from Rokko Mountains and Awaji Island, Hyogo Prefecture. B.microti Kobe type, however, has not yet been detected from the tick. On the other hand, B.microti US type and B.microti Nagano type were newly found in Ixodes persulcatus from Hokkaido and I. ovatus from Nagano Prefecture, respectively.2. Experimental infectionIn the salivary glands of unfed I, ovatus ticks, B.microti existed in the sporoblast stage in the granular acinus cells, and developed into the sporozoite stage during feeding on the experimental host for 2 days. It was strongly suggested that I. ovatus is involved in the maintenance of the parasites in the fauna of Japanese rodents.3. Further research on distribution of B.microtiRodents infected with B.microti Kobe type were found from Aomori, Shimane, Nagasaki and Kagoshima Prefectures. Rodents infected with B.microti Nagano type were also found from Nagano Prefecture. Four gene types (Otsu, Kobe, Nagano and US) of B.microti were known to distribute in Japan.