Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, USA.
Ticks Tick Borne Dis. 2010 Mar;1(1):35-43. doi: 10.1016/j.ttbdis.2009.12.002.
In the far-western United States, the nymphal stage of the western black-legged tick, Ixodes pacificus, has been implicated as the primary vector to humans of Borrelia burgdorferi sensu stricto (hereinafter referred to as B. burgdorferi), the causative agent of Lyme borreliosis in North America. In the present study, we sought to determine if infection prevalence with B. burgdorferi in I. pacificus nymphs and the density of infected nymphs differ between dense-woodland types within Mendocino County, California, and to develop and evaluate a spatially-explicit model for density of infected nymphs in dense woodlands within this high-incidence area for Lyme borreliosis. In total, 4.9% (264) of 5431 I. pacificus nymphs tested for the presence of B. burgdorferi were infected. Among the 78 sampling sites, infection prevalence ranged from 0 to 22% and density of infected nymphs from 0 to 2.04 per 100 m(2). Infection prevalence was highest in woodlands dominated by hardwoods (6.2%) and lowest for redwood (1.9%) and coastal pine (0%). Density of infected nymphs also was higher in hardwood-dominated woodlands than in conifer-dominated ones that included redwood or pine. Our spatial risk model, which yielded an overall accuracy of 85%, indicated that warmer areas with less variation between maximum and minimum monthly water vapor in the air were more likely to include woodlands with elevated acarological risk of exposure to infected nymphs. We found that 37% of dense woodlands in the county were predicted to pose an elevated risk of exposure to infected nymphs, and that 94% of the dense-woodland areas that were predicted to harbor elevated densities of infected nymphs were located on privately-owned land.
在美国远西部，太平洋革蜱的若虫阶段已被认为是将伯氏疏螺旋体（以下简称 B. burgdorferi）传播给人类的主要媒介，伯氏疏螺旋体是北美的莱姆病病原体。在本研究中，我们试图确定加利福尼亚州门多西诺县茂密林地类型内，太平洋革蜱若虫感染 B. burgdorferi 的流行率以及感染若虫的密度是否存在差异，并开发和评估一个用于该高莱姆病发病率地区茂密林地内感染若虫密度的空间显式模型。总共对 5431 只太平洋革蜱若虫进行了 4.9%（264 只）的 B. burgdorferi 感染检测。在 78 个采样点中，感染流行率范围为 0 至 22%，感染若虫密度范围为 0 至 2.04 每 100 m(2)。硬木林为主的林地感染流行率最高（6.2%），红杉林和沿海松林感染流行率最低（1.9%和 0%）。硬木林为主的林地的感染若虫密度也高于包括红杉或松树在内的针叶林为主的林地。我们的空间风险模型总体准确率为 85%，表明空气最大和最小月水汽变化较小的温暖地区更有可能包括暴露于感染若虫风险较高的林地。我们发现，该县 37%的茂密林地被预测为存在较高的感染若虫暴露风险，而预测为存在较高感染若虫密度的 94%的茂密林地都位于私人拥有的土地上。
