Abstract: Objective To establish the mosquito vector surveillance capacity in Freetown, Sierra Leone, and to investigate local mosquito density, geographical distribution, population characteristics, and seasonal fluctuations. Methods A total of nine zones were selected as mosquito surveillance sites in the western urban and rural areas of Freetown, Sierra Leone, with at least one site in each of residential areas, general working institutions, hospitals, and livestock sheds, and mosquito trap lamps were used for surveillance. Each surveillance site had 2-4 mosquito trap lamps, which were fixed in an outdoor place protected from wind, rain, and light at about 1.5 meters above the ground. The mosquito trap lamps were placed at 1 hour before sunset and the net was collected at 1 hour after sunrise in the next morning. Then the collected mosquitoes were classified by morphological characteristics in the laboratory. Mosquito surveillance was conducted once a week from June 26, 2019 to December 31, 2019. Excel 2007 software was used for the statistical analysis of mosquito vector surveillance data. Results A total of 3 012 mosquitoes were collected, among which Culex mosquitoes accounted for 84.86% and was the dominant mosquito genus in Freetown. Compared with the western urban areas, the western rural areas had significantly higher mean total mosquito density (5.01 mosquitoes/trap·night vs 3.87 mosquitoes/trap·night), mean Anopheles density (1.28 mosquitoes/trap·night vs 0.12 mosquitoes/trap·night), and composition ratio of Anopheles (1.14%-44.53% vs 0.72%-11.90%). Seasonal fluctuations of mosquito density showed that in Freetown, high mosquito density was observed during the alternate period of dry and rainy seasons in late June and early July and during the alternate period of rainy and dry seasons in late October and early November, and the lowest mosquito density was observed in late August. In addition, the seasonal fluctuation trend of Anopheles density was consistent with that of total mosquito density. A comparative analysis of different habitats showed that the livestock sheds with poor environmental sanitation and more mosquito breeding sites had a higher mosquito density (10.40 mosquitoes/trap·night), followed by residential areas (4.45 mosquitoes/trap·night) and general working institutions (2.80 mosquitoes/trap·night), and the hospitals with better environmental sanitation and fewer breeding sites had the lowest mosquito density (1.21 mosquitoes/trap·night). Conclusion The risk of mosquito bite and malaria infection in the western rural area is higher than that in the western urban area. The alternate periods from the dry season to the rainy season and from the rainy season to the dry season are important periods for the prevention and control of mosquito vectors and their infectious diseases (including malaria). Sierra Leone needs to further strengthen the management of mosquito breeding sites.

Key words: Sierra Leone, Mosquito, Surveillance, Anopheles

摘要： 目的 在塞拉利昂弗里敦地区建立蚊媒监测能力，了解当地蚊虫密度、地域分布、种群特征和季节消长等情况。方法 在塞拉利昂弗里敦市西部城区及农村共选取9个区域设置成蚊监测点，分别选择居民区、一般单位、医院和牲畜棚4类生境各不少于1处，采用诱蚊灯进行监测。每个监测点布放2~4台诱蚊灯，布灯点选择室外避风避雨避光处，诱蚊灯距离地面约1.5 m。于日落前1 h开始布放诱蚊灯，翌日日出后1 h收集诱蚊灯的集蚊网，带回实验室进行蚊种形态学鉴定。2019年6月26日至12月31日期间，每周进行1次蚊虫监测。应用Excel 2007软件对蚊媒监测数据进行统计分析。结果 共收集蚊虫3 012只，其中库蚊占捕蚊总数的84.86%，是弗里敦地区的优势蚊属。西部农村平均总蚊密度为5.01只/（灯·夜），平均按蚊密度为1.28只/（灯·夜），按蚊构成比为1.14%~44.53%，均高于西部城区平均总蚊密度[3.87只/（灯·夜）、平均按蚊密度[0.12只/（灯·夜）]和按蚊构成比（0.72%~11.90%）。蚊密度季节消长分析结果显示，塞拉利昂弗里敦地区6月底7月初旱、雨季交替时期和10月底11月初雨、旱季交替时期，蚊虫密度较高，8月下旬蚊密度最低。另外，按蚊密度季节消长趋势与总蚊密度趋势一致。不同生境比较显示，环境卫生状况较差、容易孳生蚊虫的牲畜棚蚊密度最高[10.40只/（灯·夜）]，其次是居民区和一般单位，分别为4.45和2.80只/（灯·夜）；环境卫生状况较好、孳生地较少的医院蚊密度最低[1.21只/（灯·夜）]。结论 塞拉利昂弗里敦地区西部农村被蚊虫叮咬和感染疟疾的风险比西部城区高；旱、雨季和雨、旱季交替时期是防控蚊媒及其传染病（如疟疾）的关键时期，当地需要进一步加强蚊媒孳生地管理。

关键词: 塞拉利昂, 蚊媒, 监测, 按蚊