Community and Environmental Health, College of Health Sciences, Old Dominion University, 3133A Health Sciences Building, Norfolk, Virginia 23529, USA.
Adv Exp Med Biol. 2010;673:51-65. doi: 10.1007/978-1-4419-6064-1_4.
Human monocytic ehrlichiosis (Ehrlichia chaffeensis), or HME, is a tick-transmitted, ricksettisal disease with growing impact in the United States. Risk of a tick-borne disease such as HME to humans can be estimated using the prevalence of that disease in the tick population. A deterministic model for HME is explored to investigate the underlying dynamics of prevalence in tick populations, particularly when spatial considerations are allowed. The dynamics of HME in a single spatial patch are considered first to determine which model components are most important to predicting disease dynamics in a local ecology. The model is then expanded to spatially-explicit patches on which patch connectivity, the surrounding environment and boundary effects are studied. The results of this investigation show that predicting risk of this disease to humans is determined by many complicated interactions. Areas that would be endemic in isolation may or may not sustain the disease depending on the surrounding habitat. Similarly, control efforts are shown to be far more effective when applied in wooded habitats than in neighboring grassy habitats. Boundary assumptions which describe the reality of increasing habitat fragmentation additionally play a large role in predicting the endemicity of an HME outbreak. Overall, HME and all tick-borne diseases are complex, nonlinear systems that have just begun to be explored.
人类单核细胞埃立克体病（Ehrlichia chaffeensis），或简称 HME，是一种由蜱传播的立克次氏体病，在美国的影响日益增大。可以通过蜱种群中该病的流行程度来估计人类感染蜱传疾病（如 HME）的风险。本研究利用确定性模型来研究蜱种群中 HME 流行率的潜在动态，特别是当允许考虑空间因素时。首先考虑了单一天区的 HME 动力学，以确定哪些模型组件对预测局部生态系统中的疾病动态最为重要。然后将模型扩展到具有空间变异性的斑块上，研究斑块连接、周围环境和边界效应。这项研究的结果表明，预测这种疾病对人类的风险取决于许多复杂的相互作用。在孤立状态下可能会流行的地区可能会或可能不会维持这种疾病，这取决于周围的栖息地。同样，在森林栖息地中实施的控制措施比在相邻的草地栖息地中实施的控制措施更为有效。描述栖息地破碎化增加的边界假设在预测 HME 爆发的地方性方面也起着重要作用。总体而言，HME 和所有蜱传疾病都是复杂的非线性系统，目前才刚刚开始探索。
