Data from: Tick-borne disease risk in a forest food web

Changes to the community ecology of hosts for zoonotic pathogens, particularly rodents, are likely to influence the emergence and prevalence of zoonotic diseases worldwide. However, the complex interactions between abiotic factors, pathogens, vectors, hosts, and both food resources and predators of hosts are difficult to disentangle. Here we (1) use 19 years of data from six large field plots in southeastern New York to compare the effects of hypothesized drivers of interannual variation in Lyme disease risk, including the abundance of acorns, rodents, and deer, as well as a series of climate variables; and (2) employ landscape epidemiology to explore how variation in predator community structure and forest cover influences spatial variation in the infection prevalence of ticks for the Lyme disease bacterium, Borrelia burgdorferi, and two other important tick-borne pathogens, Anaplasma phagocytophilum and Babesia microti. Acorn-driven increases in the abundance of mice were correlated with a lagged increase in the abundance of questing nymph-stage Ixodes scapularis ticks infected with Lyme disease bacteria. Abundance of white-tailed deer two years prior also correlated with increased density of infected nymphal ticks, although the effect was weak. Density of rodents in the current year was a strong negative predictor of nymph density, apparently because high current abundance of these hosts can remove nymphs from the host-seeking population. Warm, dry spring or winter weather was associated with reduced density of infected nymphs. At the landscape scale, the presence of functionally diverse predator communities or of bobcats, the only obligate carnivore, was associated with reduced infection prevalence of I. scapularis nymphs with all three zoonotic pathogens. In the case of Lyme disease, infection prevalence increased where coyotes were present but smaller predators were displaced or otherwise absent. For all pathogens, infection prevalence was lowest when forest cover within a 1km radius was high. Taken together, our results suggest that a food web perspective including bottom-up and top-down forcing is needed to understand drivers of tick-borne disease risk, a result that may also apply to other rodent-borne zoonoses. Prevention of exposure based on ecological indicators of heightened risk should help protect public health.

人畜共患病病原体（zoonotic pathogens）宿主的群落生态学变化，尤其是啮齿动物类宿主，极有可能影响全球范围内人畜共患病的出现与流行态势。然而，非生物因子、病原体、传播媒介、宿主以及宿主的食物资源与捕食者之间存在复杂的相互作用，这类作用往往难以厘清。本研究（1）利用纽约东南部6个大型野外样地长达19年的监测数据，对比分析莱姆病（Lyme disease）风险年际变化的潜在驱动因子效应，涵盖橡子、啮齿动物与鹿的种群丰度，以及一系列气候变量；（2）运用景观流行病学方法，探究捕食者群落结构与森林覆盖率的变化，如何影响蜱虫携带三种病原体的感染率空间异质性：莱姆病致病菌伯氏疏螺旋体（Borrelia burgdorferi），以及另外两种重要蜱传病原体嗜吞噬细胞无形体（Anaplasma phagocytophilum）与微小巴贝虫（Babesia microti）。
橡子丰度驱动的小鼠种群增长，与携带莱姆病致病菌的肩突硬蜱（Ixodes scapularis）寻血若虫种群丰度的滞后增长呈显著相关。两年前的白尾鹿种群丰度，同样与感染性若蜱密度升高存在关联，不过该效应强度较弱。当年啮齿动物的种群密度，是若蜱密度的强负向预测因子，究其原因，大概率是当年宿主种群丰度过高时，会将寻血宿主阶段的若蜱大量消耗，使其脱离寻血种群。温暖干燥的春季或冬季气候，与感染性若蜱密度降低存在关联。
在景观尺度下，功能多样性较高的捕食者群落，或是仅存的专性食肉动物短尾猫（bobcat）的存在，均与肩突硬蜱若蜱对三种人畜共患病病原体的感染率降低存在关联。就莱姆病而言，当郊狼种群存在而小型捕食者被排挤或缺失时，蜱虫的感染率会升高。对于所有三种病原体而言，当样地1公里半径范围内的森林覆盖率较高时，蜱虫的感染率均处于最低水平。
综合来看，本研究结果表明，若要厘清蜱传疾病风险的驱动因子，需纳入包含上行调控与下行调控的食物网研究视角，这一结论或可推广至其他啮齿动物源性人畜共患病。基于风险升高的生态学指标制定暴露预防策略，将有助于保障公众健康。