Clover J R, Lane R S
Vector-Borne Disease Section, California Department of Health Services, Sacramento, USA.
Am J Trop Med Hyg. 1995 Sep;53(3):237-40. doi: 10.4269/ajtmh.1995.53.237.
To clarify the role of nymphal versus adult western black-legged ticks (Ixodes pacificus) in the epidemiology of Lyme disease, the seasonal distribution, abundance, and spirochetal infection rates in these stages, and the seasonal occurrence of ticks biting humans and of incident cases of Lyme disease were determined in northern California. Although their seasonal activity periods overlapped for about one-third of the year, nymphs and adults predominated in different seasons, the former from late spring to summer and the latter from fall to early spring. At one site, four (4%) of 100 adults from low vegetation bordering a hardwood forest and 44 (13.6%) of 324 nymphs from leaf litter in the forest were found to contain Borrelia burgdorferi. Biting-collection records revealed that nymphs attach to people more commonly than recognized previously; I. pacificus nymphs comprised 12.5% of 967 ticks of various species and stages and 42% of all nymphs submitted for identification. Attachments by nymphs occurred primarily between April and August, which coincided with the seasonal occurrence of most incident cases of Lyme disease. Collectively, these findings strongly implicate the nymphal stage of I. pacificus as the primary vector of B. burgdorferi to humans in this region.
为阐明若虫期与成虫期的西部黑腿蜱（太平洋硬蜱）在莱姆病流行病学中的作用，研究人员在加利福尼亚州北部确定了这些阶段的季节性分布、丰度、螺旋体感染率，以及蜱叮咬人类的季节性情况和莱姆病发病病例的季节性情况。尽管若虫和成虫的季节性活动期在一年中约三分之一的时间内重叠，但若虫和成虫在不同季节占主导地位，前者从晚春到夏季，后者从秋季到早春。在一个地点，在与硬木森林接壤的低植被中的100只成虫中有4只（4%）、森林落叶层中的324只若虫中有44只（13.6%）被发现携带伯氏疏螺旋体。叮咬采集记录显示，若虫附着在人身上的情况比之前认为的更为常见；太平洋硬蜱若虫占提交鉴定的967只不同种类和阶段蜱虫的12.5%，占所有提交鉴定若虫的42%。若虫的附着主要发生在4月至8月，这与大多数莱姆病发病病例的季节性情况相吻合。总体而言，这些发现有力地表明太平洋硬蜱的若虫期是该地区伯氏疏螺旋体传播给人类的主要媒介。
