Department of Infectious Disease and Global Health, Tufts Cummings School of Veterinary Medicine, Grafton, Massachusetts, USA.
Appl Environ Microbiol. 2022 Mar 22;88(6):e0239121. doi: 10.1128/aem.02391-21. Epub 2022 Jan 5.
In the northeastern United States, the emergence of Lyme disease has been associated, in part, with the increase of small forest patches. Such disturbed habitat is exploited by generalist species, such as white-footed mice, which are considered the host with the greatest reservoir capacity for the agents of Lyme disease (Borrelia burgdorferi ) and human babesiosis (Babesia microti). Spatial risk analyses have identified edge habitat as particularly risky. Using a retrotransposon-based quantitative PCR assay for host bloodmeal remnant identification, we directly measured whether the hosts upon which vector ticks fed differed at the edge or within the contiguous small habitat patch. Questing nymphal deer ticks, Ixodes dammini, the northern clade of Ixodes scapularis, were collected from either the edge or within a thicket on Nantucket Island over 3 transmission seasons and tested for evidence of infection as well as bloodmeal hosts. Tick bloodmeal hosts significantly differed by site as well as by year. Mice and deer were identified most often (49.9%), but shrews, rabbits, and birds were also common. Ticks from the edge fed on a greater diversity of hosts than those from the thicket. Surprisingly, mice were not strongly associated with either infection at either sampling site (odds ratio [OR] < 2 for all). Although shrews were not the most common host utilized by ticks, they were highly associated with both infections at both sites (OR = 4.5 and 11.0 for B. burgdorferi and 7.9 and 19.0 for B. microti at the edge and thicket, respectively). We conclude that reservoir hosts may differ in their contributions to infecting ticks between edge and contiguous vegetated patches. Habitat fragmentation is thought to be a main factor in the emergence of Lyme disease and other deer tick-transmitted infections. The patchwork of forest and edges promotes altered biodiversity, favoring the abundance of generalist rodents, such as white footed mice, heretofore considered a key tick and reservoir host in the northeastern United States. We used tick bloodmeal analyses to directly identify the hosts from which nymphal deer ticks became infected. We demonstrate that there is considerable microfocality in host contributions to the cohort of infected ticks and that shrews, although they fed fewer ticks than mice, disproportionately influenced the force of pathogen transmission in our site. The venue of transmission of certain deer tick-transmitted agents may comprise a habitat scale of 10 m or fewer and depend on alternative small mammal hosts such as shrews.
在美国东北部，莱姆病的出现部分与小森林斑块的增加有关。这种被干扰的栖息地被多面手物种利用，例如白足鼠，它们被认为是莱姆病（伯氏疏螺旋体）和人类巴贝虫病（微小巴贝虫）病原体的宿主中具有最大储存能力的宿主。空间风险分析已确定边缘生境特别危险。使用基于反转录转座子的定量 PCR 检测宿主血液残留鉴定，我们直接测量了在边缘或连续小生境斑块内，寄生于媒介蜱的宿主是否存在差异。从 3 个传播季节中从楠塔基特岛的边缘或灌木丛中收集到的鹿蜱幼体，即伊蚊属 dammini ，伊蚊属 scapularis 的北方分支，并对其感染证据和血液宿主进行了测试。蜱的血液宿主因地点和年份而异。老鼠和鹿最常见（49.9％），但也有鼩鼱，兔子和鸟类。与灌木丛中的蜱相比，边缘上的蜱以更大的多样性为食。令人惊讶的是，老鼠与两个采样点的任何感染都没有密切关系（所有比值比[OR]均<2）。尽管鼩鼱不是蜱最常利用的宿主，但它们与两个地点的两种感染都高度相关（边缘和灌木丛的 OR 分别为 4.5 和 11.0 ，以及 7.9 和 19.0 ）。我们得出的结论是，在边缘和连续植被斑块之间，储存宿主可能在感染蜱的贡献方面有所不同。 人们认为，栖息地破碎化是莱姆病和其他鹿蜱传播感染出现的主要因素。森林和边缘的拼凑促进了生物多样性的改变，有利于普通啮齿动物（例如白足鼠）的丰富，这些啮齿动物迄今被认为是美国东北部关键的蜱和储存宿主。我们使用蜱的血液分析直接鉴定了感染幼蜱的宿主。我们证明，宿主对感染蜱的群体的贡献存在很大的微观焦点，并且尽管鼩鼱的蜱数量少于老鼠，但它们在我们的地点中对病原体传播的力量产生了不成比例的影响。某些鹿蜱传播剂的传播场所可能包含 10 米或更小的栖息地规模，并取决于其他小型哺乳动物宿主，例如鼩鼱。
