MacDonald Andrew J, Briggs Cheryl J
Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 93106-9620, United States.
Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 93106-9620, United States.
Ticks Tick Borne Dis. 2016 Feb;7(1):234-242. doi: 10.1016/j.ttbdis.2015.10.016. Epub 2015 Oct 25.
Patterns of seasonal activity and density of host-seeking western blacklegged ticks, Ixodes pacificus, were investigated in central and southern California. Weekly to monthly drag sampling was undertaken at two sites in Santa Barbara County and one site in Los Angeles County over multiple years. Adult I. pacificus became active in the winter (late November) and were rare or absent by late April to early May. Nymphal ticks became active in early to late February, were absent by early May to early June, and were rarely encountered using the drag method throughout their period of peak seasonal activity. Larval ticks became active earlier in the season, or at the same time as nymphs (early to late February) and were absent by early May. These results suggest a highly truncated period of I. pacificus seasonal questing activity, particularly apparent in the juvenile tick stages, in central and southern California relative to observed patterns in Lyme-endemic northwestern California. Notably, the highly truncated period of questing activity of the juvenile stages has important implications for pathogen transmission dynamics in that there exists only a brief window for horizontally transmitted pathogens to be acquired by one tick cohort and subsequently transmitted, through hosts, to the next tick cohort in this system. The broader patterns observed also suggest low human risk of tick-borne disease in central and southern California, and have implications for reduced tick-borne disease risk in the western US more generally under projected climate change.
在加利福尼亚州中部和南部，对寻找宿主的太平洋硬蜱（Ixodes pacificus）的季节性活动模式和密度进行了调查。多年来，在圣巴巴拉县的两个地点和洛杉矶县的一个地点进行了每周至每月一次的拖网采样。成年太平洋硬蜱在冬季（11月下旬）开始活跃，到4月下旬至5月初则很少见或消失。若蜱在2月初至下旬开始活跃，5月初至6月初消失，在其季节性活动高峰期，用拖网法很少能发现它们。幼蜱在季节早期或与若蜱同时（2月初至下旬）开始活跃，5月初消失。这些结果表明，相对于在莱姆病流行的加利福尼亚州西北部观察到的模式，加利福尼亚州中部和南部的太平洋硬蜱季节性搜寻活动期大幅缩短，在幼蜱阶段尤为明显。值得注意的是，幼蜱阶段搜寻活动期的大幅缩短对病原体传播动态具有重要影响，因为在这个系统中，水平传播的病原体只有很短的窗口期被一个蜱虫群体获取，然后通过宿主传播给下一个蜱虫群体。观察到的更广泛模式还表明，加利福尼亚州中部和南部人类感染蜱传疾病的风险较低，并且在预计的气候变化下，对更广泛的美国西部蜱传疾病风险降低具有影响。
