Comparative ecological analysis and predictive modeling of tick-borne pathogens

Tick-borne diseases constitute the predominant vector-borne health threat in North America. Recent observations have noted a significant expansion in the range of the black-legged tick (Ixodes scapularis Say, Acari: Ixodidae), alongside a rise in the incidence of diseases caused by its vectored pathogens: Borrelia burgdorferi (Spirochaetales: Spirochaetaceae), Babesia microti (Piroplasmida: Babesiidae), and Anaplasma phagocytophilium (Rickettsiales: Anaplasmataceae), the causative agents of Lyme disease, babesiosis, and anaplasmosis, respectively. Prior research identified environmental features that influence the ecological dynamics of I. scapularis and B. burgdorferi that can be used to predict the distribution and abundance of these organisms, and thus Lyme disease risk. In contrast, there is a paucity of research into the environmental determinants of B. microti and A. phagocytophilium. Here we use over a decade of surveillance data to model the impact of environmental features on the infection prevalence of these increasingly common human pathogens in ticks across New York State (NYS). Our findings reveal a consistent northward and westward expansion of B. microti in NYS from 2009 to 2019, while the range of A. phagocytophilum varied at fine spatial scales. We constructed biogeographic models using data from over 1000 site-year visits and encompassing more than 250 environmental variables to accurately forecast infection prevalence for each pathogen to future years that were not included in model training. Several environmental features were identified to have divergent effects on the pathogens, revealing potential ecological differences governing their distribution and abundance. These validated biogeographic models are immediately useful for disease prevention efforts.

蜱媒疾病是北美地区最主要的虫媒健康威胁。近期观测显示，黑腿蜱（*Ixodes scapularis* Say，蜱螨目：硬蜱科）的分布范围显著扩张，其传播的病原体所引发的疾病发病率亦随之上升：分别为伯氏疏螺旋体（*Borrelia burgdorferi*，螺旋体目：螺旋体科）、微小巴贝西虫（*Babesia microti*，梨形虫目：巴贝西科）以及嗜吞噬细胞无形体（*Anaplasma phagocytophilium*，立克次体目：无形体科），它们分别是莱姆病、巴贝西虫病和无形体病的致病菌。既往研究已明确可影响黑腿蜱与伯氏疏螺旋体生态动态的环境特征，并借此预测二者的分布与种群丰度，进而评估莱姆病的传播风险。与之相对，针对微小巴贝西虫与嗜吞噬细胞无形体的环境影响因素的研究仍较为匮乏。本研究依托十余年的监测数据，针对美国纽约州（NYS）范围内蜱虫体内这些日益常见的人类病原体的感染率，建模分析环境特征的影响效应。研究结果显示，2009年至2019年间，纽约州内微小巴贝西虫的分布范围呈现持续向北、向西扩张的趋势，而嗜吞噬细胞无形体的分布范围则在精细空间尺度上存在波动。本研究基于超1000次站点-年度采样数据，纳入超过250项环境变量构建生物地理模型，可精准预测训练集以外未来年份各病原体的感染率。研究还发现多项环境特征对不同病原体的影响存在差异，揭示了调控二者分布与种群丰度的潜在生态学机制差异。这些经过验证的生物地理模型可直接服务于疾病防控工作。