McLean D M, Cobb C, Gooderham S E, Smart C A, Wilson A G, Wilson W E
Can Med Assoc J. 1967 Mar 18;96(11):660-4.
Powassan virus isolations were achieved from three of 60 pools of Ixodes cookei ticks removed from 286 groundhogs (Marmota monax) which were collected some 200 miles north of Toronto between May 5 and September 5, 1966. Virus yields per pool of one to 11 ticks ranged from 10(2.5) to 10(6.0) TCD(50) for primary swine kidney tissue cultures, and positive pools were collected on June 24, July 15 and August 10. Powassan neutralizing antibodies were detected by mouse inoculation tests in 143 of 362 animals including 127 of 286 groundhogs, 14 of 45 red squirrels (Tamiasciurus hudsonicus) and two of 31 other forest mammals. The monthly prevalence of antibody in the current season's groundhogs increased from 0 to 25% with the progression of summer, but in older animals the incidence remained between 38 and 62% throughout the season. These results substantiate earlier findings which pointed towards the maintenance of Powassan virus in nature by a cycle involving groundhogs and squirrels as reservoirs, with ticks as vectors, from which human infections occurred tangentially.
1966年5月5日至9月5日期间，在多伦多以北约200英里处捕获的286只土拨鼠（Marmota monax）身上采集了60组库克硬蜱（Ixodes cookei），其中有3组分离出了波瓦桑病毒。每组1至11只蜱在原代猪肾组织培养中的病毒产量为10(2.5)至10(6.0)半数组织培养感染剂量（TCD50），阳性组分别于6月24日、7月15日和8月10日采集。通过小鼠接种试验在362只动物中的143只检测到了波瓦桑中和抗体，其中包括286只土拨鼠中的127只、45只红松鼠（Tamiasciurus hudsonicus）中的14只以及31只其他森林哺乳动物中的2只。随着夏季的推进，当季土拨鼠抗体的月度流行率从0升至25%，但在年龄较大的动物中，整个季节的发病率仍在38%至62%之间。这些结果证实了早期的研究发现，即波瓦桑病毒在自然界中通过一个以土拨鼠和松鼠为宿主、蜱为传播媒介的循环得以维持，人类感染是偶然发生的。
