Department of Mathematics and Statistics, California State University Chico, CA, United States.
Department of Geography, Dartmouth College, Hanover, NH, United States.
Ticks Tick Borne Dis. 2021 Jul;12(4):101724. doi: 10.1016/j.ttbdis.2021.101724. Epub 2021 Apr 13.
The literature on Lyme disease includes a lively debate about the paradoxical role of changing deer populations. A decrease in the number of deer will both (1) reduce the incidence of Lyme disease by decreasing the host populations for ticks and therefore tick populations, and (2) enhance the incidence of Lyme disease by offering fewer reservoir-incompetent hosts for ticks, forcing the vector to choose reservoir-competent, and therefore possibly diseased, hosts to feed on. A review of field studies exploring the net impact of changing deer populations shows mixed results. In this manuscript, we investigate the hypothesis that the balance of these two responses to changing deer populations depends on the relative population sizes of reservoir-competent vs. reservoir-incompetent hosts and the presence of host preference in larval and adult stages. A temperature driven seasonal model of Borrelia burgdorferi sensu stricto (cause of Lyme disease) transmission among three host types (reservoir-competent infected and uninfected hosts, and reservoir-incompetent hosts) is constructed as a system of nonlinear ordinary differential equations. The model, which produces biologically reasonable results for both the tick vector Ixodes scapularis Say 1921 and the hosts, is used to investigate the effects of reservoir-incompetent host removal on both tick populations and disease prevalence for various relative population sizes of reservoir-competent hosts vs. reservoir-incompetent hosts. In summary, the simulation results show that the model with host preference appears to be more accurate than the one with no host preference. Given these results, we found that removal of adult I. scapularis(Say) hosts is likely to reduce questing nymph populations. At very low levels questing adult abundance may rise with lack of adult hosts. There is a dilution effect at low reservoir-competent host populations and there is an amplification effect at high reservoir-competent host populations.
莱姆病的文献中包含了一场关于不断变化的鹿群的矛盾作用的激烈争论。鹿的数量减少会通过减少蜱虫和因此蜱虫的宿主种群，（1）降低莱姆病的发病率，以及（2）通过为蜱虫提供较少的非储存宿主，迫使媒介选择储存能力强的、可能患病的宿主来吸血，从而增加莱姆病的发病率。对探索不断变化的鹿群的净影响的实地研究的综述显示出混合的结果。在本文中，我们研究了以下假设：这两种对不断变化的鹿群的反应的平衡取决于储存能力宿主与非储存能力宿主的相对种群大小，以及幼虫和成虫阶段宿主偏好的存在。构建了一个由三种宿主类型（储存能力宿主感染和未感染宿主，以及非储存能力宿主）组成的博氏疏螺旋体（莱姆病的病因）在温度驱动的季节性传播的非线性常微分方程组模型。该模型对伊氏扇头蜱和宿主都产生了合理的生物学结果，用于研究非储存能力宿主的去除对各种储存能力宿主与非储存能力宿主的相对种群大小的蜱虫种群和疾病流行率的影响。总之，模拟结果表明，具有宿主偏好的模型似乎比没有宿主偏好的模型更准确。鉴于这些结果，我们发现，去除成年伊氏扇头蜱（Say）宿主可能会减少幼蜱的数量。在非常低的水平下，由于缺乏成年宿主，成虫的数量可能会增加。在低储存能力宿主种群中存在稀释效应，在高储存能力宿主种群中存在放大效应。
