Diagnosis and prevention of viral tick-borne encephalitis in Hokkaido

在发现蜱传脑炎患者的流行疫源地和北海道其他地区进行了蜱传脑炎流行病学调查。结果总结如下：1) 1995年，从发现病人的地区饲养的哨岗犬的血液中分离出三株蜱传脑炎病毒。2)从600只卵硬蜱中分离到2株蜱传脑炎，野外感染率为0.3%（2/600）。3)从啮齿动物中分离到2株蜱传脑炎病毒，分别为斑姬鼠和鲁法克氏蜱。4)从犬、蜱和啮齿动物中分离的病毒株经鉴定为俄罗斯春夏脑炎型蜱传脑炎病毒。5)病毒流行区主要分布在北海道南部4个区。上述结果表明，蜱传脑炎病毒在北海道地区存在地方性流行，并通过蜱、卵、伊蚊和啮齿动物传播。

Epidemiological investigations of tick-borne encephalitis were performed in the endemic foci where the tick-borne encephalitis patient was found and also in the other areas in Hokkaido. Results wre summarized as follows.1) In 1995, three strains of tick-borne enchephalitis virus were isolated from the blood of the sentinel dogs which were kept in the area where the patient was found.2) Two strains of tick-borne encephalitis were isolated from 600 individuals of Ixodes ovatus ticks, giving a field infection rate of 0.3% (2/600).3) Two strains of tick-borne encephalitis virus were isolated from rodents, one from Apodemus speciosus and another from Clethrionomis rufocanus.4) Virus strains isolated from dogs, ticks and rodents were identifiend as Russian Spring Summer encephalitis type of tick-borne encephalitis virus.5) Endemic ares of the virus were distributed in 4 districs of southern Hokkaido. These results indicate that tick-borne encephalitis virus is endemic in Hokkaido and maintained by the vector ticks Ixodes ovatus and rodents.