Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA.
J Med Entomol. 2009 Nov;46(6):1519-31. doi: 10.1603/033.046.0641.
We examined seasonal patterns for entomological measures of risk for exposure to Culex vectors and West Nile virus (family Flaviviridae, genus Flavivirus, WNV) in relation to human WNV disease cases in a five-county area of northeastern Colorado during 2006-2007. Studies along habitat/elevation gradients in 2006 showed that the seasonal activity period is shortened and peak numbers occur later in the summer for Culex tarsalis Coquillett females in foothills-montane areas >1600 m compared with plains areas <1600 m in Colorado's Front Range. Studies in the plains of northeastern Colorado in 2007 showed that seasonal patterns of abundance for Cx. tarsalis and Culex pipiens L. females differed in that Cx. tarsalis reached peak abundance in early July (mean of 328.9 females per trap night for 18 plains sites), whereas the peak for Cx. pipiens did not occur until late August (mean of 16.4 females per trap night). During June-September in 2007, which was a year of intense WNV activity in Colorado with 578 reported WNV disease cases, we recorded WNV-infected Cx. tarsalis females from 16 of 18 sites in the plains. WNV infection rates in Cx. tarsalis females increased gradually from late June to peak in mid-August (overall maximum likelihood estimate for WNV infection rate of 8.29 per 1000 females for the plains sites in mid-August). No WNV-infected Culex mosquitoes were recorded from sites >1600 m. The vector index for abundance of WNV-infected Cx. tarsalis females for the plains sites combined exceeded 0.50 from mid-July to mid-August, with at least one site exceeding 1.00 from early July to late August. Finally, we found that abundance of Cx. tarsalis females and the vector index for infected females were strongly associated with weekly numbers of WNV disease cases with onset 4-7 wk later (female abundance) or 1-2 wk later (vector index).
我们研究了 2006 年至 2007 年科罗拉多州东北部五县地区蚊媒与人类西尼罗河病毒（黄病毒科、黄病毒属、西尼罗河病毒）暴露风险的昆虫学指标的季节性模式。2006 年，在生境/海拔梯度上的研究表明，与科罗拉多州落基山脉平原地区（<1600 米）相比，丘陵-山地地区（>1600 米）的库蚊（Culex tarsalis Coquillett 雌蚊）的季节性活动期缩短，夏季高峰期出现较晚。2007 年，在科罗拉东北部平原地区的研究表明，库蚊和库蚊（Culex pipiens L.）雌蚊的丰度季节性模式不同，库蚊于 7 月初达到丰度高峰（18 个平原站点的每个诱蚊笼夜 328.9 只雌蚊），而库蚊的高峰直到 8 月下旬才出现（每个诱蚊笼夜 16.4 只雌蚊）。2007 年 6 月至 9 月，科罗拉多州西尼罗河病毒活动非常活跃，报告了 578 例西尼罗河病毒病病例，我们在 18 个平原站点中的 16 个站点记录到了感染西尼罗河病毒的库蚊雌蚊。6 月下旬至 8 月中旬，库蚊雌蚊的西尼罗河病毒感染率逐渐升高，8 月中旬达到高峰（平原站点的西尼罗河病毒感染率总体最大似然估计值为 8.29/1000 只雌蚊）。在海拔>1600 米的站点没有记录到感染西尼罗河病毒的库蚊。7 月中旬至 8 月中旬，平原站点感染西尼罗河病毒的库蚊丰度的媒介指数超过 0.50，至少有一个站点从 7 月初到 8 月底超过 1.00。最后，我们发现库蚊雌蚊丰度和感染雌蚊的媒介指数与 4-7 周后（雌蚊丰度）或 1-2 周后（媒介指数）出现的西尼罗河病毒病病例周数呈强相关。
