Bacterial Diseases Branch, Division of Vector Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 3150 Rampart Road, Fort Collins, CO, USA.
J Med Entomol. 2011 Jul;48(4):884-90. doi: 10.1603/me11005.
The American dog tick, Dermacentor variabilis (Say) (Acari: Ixodidae), has been implicated as a potential bridging vector to humans of Francisella tularensis, the etiological agent of tularemia. Since the initial studies evaluating vector competency of D. variabilis were conducted, F. tularensis has been subdivided into subspecies and clades that differ in their geographical distribution in the United States and in the severity of infections caused in humans. Here, we demonstrate that D. variabilis nymphs efficiently acquire, transtadially maintain, and transmit each of the strains tested (clades A1b and A2, and type B). Transmission efficiency by adult females was similarly high among infection groups and ranged from 58% for type B to 89% for A2 infections. In addition, we demonstrated that transmission can occur shortly after tick attachment. These findings support the concept that D. variabilis adults may play a significant role in epizootic transmission of F. tularensis, and as a bridging vector to humans.
美洲犬蜱，即变色革蜱（Say）（蜱螨目：硬蜱科），被认为是土拉弗朗西斯菌（造成兔热病的病原体）向人类传播的潜在媒介。自最初评估变色革蜱媒介效能的研究开展以来，土拉弗朗西斯菌已被分为亚种和进化枝，它们在美国的地理分布以及在人类中引起的感染严重程度上存在差异。在这里，我们证明了变色革蜱若虫能够有效地获取、经卵传递并维持所测试的每个菌株（A1b 和 A2 进化枝以及 B 型）。雌性成虫的传播效率在感染组之间也非常高，范围从 B 型的 58%到 A2 感染的 89%。此外，我们还证明了在蜱虫附着后不久就可以发生传播。这些发现支持了这样一种概念，即变色革蜱成虫可能在土拉弗朗西斯菌的爆发性传播中以及作为向人类传播的媒介中发挥重要作用。
