Stafford Kirby C, Denicola Anthony J, Kilpatrick Howard J
Connecticut Agricultural Experiment Station, 123 Huntington Street, Box 1106, New Haven, CT 06504, USA.
J Med Entomol. 2003 Sep;40(5):642-52. doi: 10.1603/0022-2585-40.5.642.
The principal vector for the pathogens of Lyme disease, human granulocytic ehrlichiosis, and human babesiosis is the tick Ixodes scapularis Say. A chalcid wasp, Ixodiphagus hookeri, in the family Encyrtidae parasitizes populations of the tick on several islands or other geographically isolated sites in New England with high densities of these ticks and white-tailed deer (Odocoileus virginianus), the principal host for adult I. scapularis. Deer densities were reduced at a forested tract in Bridgeport and the Bluff Point Coastal Reserve in Groton, Connecticut, from levels exceeding 90 animals per km2 in 1992 (Bridgeport) and 1994 (Bluff Point) to 17 and 10 animals per km2, respectively, by fall 2001. Tick densities declined with sustained reductions in the population of white-tailed deer. Similarly, prevalence of tick parasitism by Ixodes hookeri declined at both sites from 30 to 25% to <1.0% and was significantly correlated with previous year's deer density at both sites (r(s) = 0.933 and r(s) = 0.867, P < or = 0.0001) and with nymphal tick densities at Bridgeport (r(s) = 0.867, P < or = 0.0001), but was not as well correlated with tick densities in Groton. The virtual disappearance of I. hookeri in this study corresponds with a lack of I. hookeri in mainland I. scapularis at comparable deer and tick densities, suggesting that there is a threshold deer density of approximatley 10-20/km2, with corresponding tick densities necessary for I. hookeri to successfully parasitize I. scapularis.
莱姆病、人粒细胞埃立克体病和人巴贝斯虫病病原体的主要传播媒介是肩突硬蜱（Ixodes scapularis Say）。小蜂科的一种小蜂——钩状嗜蜱姬小蜂（Ixodiphagus hookeri）寄生于新英格兰地区几个岛屿或其他地理隔离地点的蜱虫种群，这些地方蜱虫和白尾鹿（弗吉尼亚鹿，Odocoileus virginianus）密度很高，而白尾鹿是成年肩突硬蜱的主要宿主。康涅狄格州布里奇波特的一片森林区域以及格罗顿的布拉夫角海岸保护区的鹿密度从1992年（布里奇波特）和1994年（布拉夫角）每平方公里超过90只动物，分别降至2001年秋季的每平方公里17只和10只。随着白尾鹿数量持续减少，蜱虫密度也随之下降。同样，两个地点钩状嗜蜱姬小蜂对蜱虫的寄生率从30%降至25%，再降至<1.0%，并且与两个地点上一年的鹿密度显著相关（斯皮尔曼相关系数r(s) = 0.933和r(s) = 0.867，P≤0.0001），与布里奇波特若蜱密度也显著相关（r(s) = 0.867，P≤0.0001），但与格罗顿的蜱虫密度相关性没那么好。本研究中钩状嗜蜱姬小蜂几乎消失，这与大陆上肩突硬蜱在类似鹿和蜱密度情况下缺乏钩状嗜蜱姬小蜂的情况相符，这表明存在一个大约每平方公里10 - 20只鹿的密度阈值，以及相应的蜱虫密度，才能使钩状嗜蜱姬小蜂成功寄生于肩突硬蜱。
