Viral Special Pathogens Branch, Centers for Disease Control and Prevention, Atlanta, GA, United States of America.
Department of Animal Health, Faculty of Veterinary Medicine, University of Zaragoza, Zaragoza, Spain.
PLoS Negl Trop Dis. 2018 Feb 8;12(2):e0006248. doi: 10.1371/journal.pntd.0006248. eCollection 2018 Feb.
Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne zoonotic agent that is maintained in nature in an enzootic vertebrate-tick-vertebrate cycle. Hyalomma genus ticks have been implicated as the main CCHFV vector and are key in maintaining silent endemic foci. However, what contributes to their central role in CCHFV ecology is unclear. To assess the significance of host preferences of ticks in CCHFV ecology, we performed comparative analyses of hosts exploited by 133 species of ticks; these species represent 5 genera with reported geographical distribution over the range of CCHFV. We found that the composition of vertebrate hosts on which Hyalomma spp. feed is different than for other tick genera. Immatures of the genus Hyalomma feed preferentially on species of the orders Rodentia, Lagomorpha, and the class Aves, while adults concentrate mainly on the family Bovidae. With the exception of Aves, these hosts include the majority of the vertebrates consistently reported to be viremic upon CCHFV infection. While other tick genera also feed on these hosts, Hyalomma spp. almost completely concentrate their populations on them. Hyalomma spp. feed on less phylogenetically diverse hosts than any other tick genus, implying that this network of hosts has a low resilience. Indeed, removing the most prominent hosts quickly collapsed the network of parasitic interactions. These results support the intermittent activity of CCHFV foci: likely, populations of infected Hyalomma spp. ticks exceed the threshold of contact with humans only when these critical hosts reach adequate population density, accounting for the sporadic occurence of clinical tick-transmitted cases. Our data describe the association of vertebrate host preferences with the role of Hyalomma spp. ticks in maintaining endemic CCHFV foci, and highlight the importance of host-tick dynamics in pathogen ecology.
克里米亚-刚果出血热病毒（CCHFV）是一种蜱传动物源病原体，在自然环境中以脊椎动物-蜱-脊椎动物的地方性流行循环形式存在。璃眼蜱属蜱种被认为是 CCHFV 的主要传播媒介，在维持无声地方性流行焦点中起着关键作用。然而，它们在 CCHFV 生态学中发挥核心作用的原因尚不清楚。为了评估蜱在 CCHFV 生态学中宿主偏好的重要性，我们对 133 种蜱种利用的宿主进行了比较分析；这些物种代表了 5 个属，其地理分布范围涵盖了 CCHFV 的范围。我们发现，璃眼蜱属蜱种取食的脊椎动物宿主组成与其他蜱属不同。璃眼蜱属的若虫优先取食啮齿目、兔形目和鸟类目物种，而成虫则主要集中在牛科。除鸟类外，这些宿主包括在 CCHFV 感染后一直被报告为病毒血症的大多数脊椎动物。虽然其他蜱属也以这些宿主为食，但璃眼蜱属几乎完全集中在它们身上。璃眼蜱属取食的宿主在进化上比任何其他蜱属都更为多样化，这意味着这个宿主网络的弹性较低。事实上，去除最主要的宿主会迅速使寄生虫相互作用的网络崩溃。这些结果支持 CCHFV 流行焦点的间歇性活动：可能只有当这些关键宿主达到足够的种群密度时，感染的璃眼蜱属蜱种群才会超过与人类接触的阈值，从而解释了临床蜱传病例的偶发性发生。我们的数据描述了脊椎动物宿主偏好与璃眼蜱属蜱在维持地方性 CCHFV 流行焦点中的作用之间的关系，并强调了宿主-蜱动态在病原体生态学中的重要性。
