Epidemiological studies on babesiosis in humans and wild-life animals in Japan

我们对1999年在日本兵库县神户市发生的第一例有症状的人类巴贝斯虫病进行了调查。我们证明，病人是通过输血从一个长期携带巴贝斯虫寄生虫的无症状个体捐献的血液感染的。我们能够从患者和供血者身上分离出微小巴贝虫样寄生虫，方法是使用SCID小鼠，将其循环红细胞替换为人类红细胞。流行病学调查显示，日本巴贝斯虫的主要宿主是日本大型田鼠，其中有神户型和鹤别型两种本土类巴贝斯虫寄生虫。这两种类型在血清学和基因特征上彼此不同，也不同于在人类巴贝斯虫病流行的美国东北部分离到的美国型微贝斯虫分离株。1983年对某蜱传疾病流行区采集的人血清进行回顾性血清流行病学调查，发现血清流行率为1.8%，表明早在该指示病例发生之前，日本就存在人类巴贝斯虫病。据推测，日本的霍别蜱和美国型寄生虫的蜱媒分别为卵形伊蚊和过弯伊蚊。神户型寄生虫的蜱媒尚未确定。

We have investigated on the first symptomatic human babesiosis case that occurred in 1999 at Kobe City, Hyogo Prefecture, Japan. We proved that the patient was infected by transfusion of the blood donated from an asymptomatic individual who was a long-term carrier of Babesia parasites. We were able to isolate Babesia microti-like parasites from both the patient and the blood donor by using the SCID mice whose circulating erythrocytes were replaced with human erythrocytes. Epizootiologic survey showed that the major reservoir of Babesia parasites in Japan was the large Japanese field mouse, Apodemus speciosus, which harvard two types of indigenous B. microti-like parasites, namely Kobe and Hobetsu types. Both types were serologically and genotypically distinct from each other and from the U.S.-type B. microti isolates that were isolated in the northeastern United States where human babesiosis is endemic. Retrospective seroepidemiological survey of human serum collected in 1983 from a tick borne-disease endemic region revealed seroprevalance of 1.8%, with demonstrating that human babesiosis existed in Japan long before the index case occurred. The tick vector of Hobetsu- and U.S.-type parasites in Japan was presumed to be Ixodes ovatus and Ixodes persulcatus, respectively. The tick vector of Kobe-type parasites has not yet been determined.