Fofana D, Koné Ab, Konan Yl, Konan Kl, Doannio Jmc, N'goran Ek
Laboratoire de zoologie et de biologie animale de l'UFR Biosciences Université d'Abidjan-Cocody 22 BP 582 Abidjan 22 Côte d'Ivoire.
Sante. 2010 Apr-Jun;20(2):73-9. doi: 10.1684/san.2010.0183. Epub 2010 Aug 5.
The ecological and climatic variations in tropical areas of Africa make the transmission of malaria very heterogeneous. Several species of mosquitoes of the Anopheles genus transmit the disease. In Côte d'Ivoire, studies in the southern and northern forests have shown the involvement of Anopheles gambiae, An. funestus and An. nili in this transmission. This study was conducted in N'gatty and Allaba, two villages in a lagoon area of southern Côte d'Ivoire, in the district of Dabou. The district is located between 05 degrees 18 N and 04 degrees 27 W, about 40 kilometres from the economic capital of Côte d'Ivoire, and has a surface of 2257.8 km2. Two lagoon villages, N'gatty and Allaba, about a kilometre apart, were selected as sites for this research. The topography of N'gatty is rugged, with two important sides: a banana plantation on the west and the lagoon on the east, covered by aquatic plants (Pistia stratiotes, Acrosticum aureum, nympheacae and Eichhornia crassipes). This aquatic vegetation separates the last plots of the village from the lagoon. Mosquito populations were sampled from December 2007 through September 2008 by nighttime captures on volunteers three consecutive nights each month, inside six living rooms (4 in N'gatty and 2 in Allaba, a smaller village). The mosquitoes were captured when they landed on the volunteer's legs. There were two teams of catchers for each home; the first worked from 18:00 h to 24:00 and the second from 24:00 to 06:00. The ovaries and glands of An. gambiae were dissected. The physiological age of the females was determined by the appearance of the trachea on ovarian dissection. The sporozoites were sought by optic microscopy in cooled glands in a drop of physiological salt solution. During the 10 months of this study, 21 137 mosquitoes were caught in N'gatty and 7163 in Allaba. An. gambiae species accounted for less than 2% of the mosquito fauna in the two villages. Overall, the average bite rate was 203.24 bites per man per night (b/m/n) in N'gatty and 137.75 in Allaba. The average number of An. gambiae bites was 4.04 b/m/n in N'gatty and 2 b/m/n in Allaba. Annually, the average An. gambiae bites totalled 1474.6 bites per man per year (b/m/y) in N'gatty and 730 in Allaba. No An. funestus mosquito was caught in Allaba, and its average number of bites per man per year in N'gatty was only 3.65. No infected glands (n = 420 dissected) were found in N'gatty throughout the investigation. The mean sporozoite rate in Allaba was only 0.285% (n = 104). The mean entomological inoculation rate (EIR) was estimated at 0.017 infecting bites per man and per night (ib/m/n) in N'Gatty and 6.2 in Allaba. This weak entomological inoculation rate leads us to consider continuing the research for infection of An. gambiae by ELISA techniques. In conclusion, malaria transmission by An. gambiae in this area is very low.
非洲热带地区的生态和气候差异使得疟疾传播情况极为不均一。按蚊属的几种蚊子传播这种疾病。在科特迪瓦,对南部和北部森林的研究表明冈比亚按蚊、 嗜人按蚊和尼罗按蚊参与了这种传播。本研究在科特迪瓦南部泻湖地区达布区的两个村庄恩加蒂和阿拉巴进行。该地区位于北纬5度18分和西经4度27分之间,距离科特迪瓦的经济首都约40公里,面积为2257.8平方公里。相距约一公里的两个泻湖村庄恩加蒂和阿拉巴被选为这项研究的地点。恩加蒂的地形崎岖,有两个重要区域:西边是一个香蕉种植园,东边是泻湖,覆盖着水生植物(大薸、 黄金凤、睡莲和凤眼莲)。这片水生植被将村庄的最后几块地与泻湖隔开。2007年12月至2008年9月,通过每月连续三个晚上在六间起居室(恩加蒂4间,较小的阿拉巴村2间)内对志愿者进行夜间捕捉来采集蚊虫种群。蚊子落在志愿者腿上时将其捕获。每个住所设有两个捕捉小组;第一组从18:00工作至24:00,第二组从24:00工作至06:00。解剖冈比亚按蚊的卵巢和腺体。通过卵巢解剖时气管的外观来确定雌蚊的生理年龄。在一滴生理盐溶液中,通过光学显微镜在冷却的腺体中寻找子孢子。在本研究的10个月期间,恩加蒂捕获了21137只蚊子,阿拉巴捕获了7163只。冈比亚按蚊在这两个村庄的蚊虫动物群中所占比例不到2%。总体而言,恩加蒂的平均叮咬率为每人每晚203.24次叮咬(b/m/n),阿拉巴为137.75次。恩加蒂冈比亚按蚊的平均叮咬次数为4.04 b/m/n,阿拉巴为2 b/m/n。每年,恩加蒂冈比亚按蚊的平均叮咬次数总计为每人每年1474.6次叮咬(b/m/y),阿拉巴为730次。在阿拉巴未捕获到嗜人按蚊,其在恩加蒂每人每年的平均叮咬次数仅为3.65次。在整个调查过程中,恩加蒂未发现受感染的腺体(解剖了420个)。阿拉巴的平均子孢子率仅为0.285%(n = 104)。恩加蒂的平均昆虫接种率(EIR)估计为每人每晚0.017次感染性叮咬(ib/m/n),阿拉巴为6.2次。这种较低的昆虫接种率使我们考虑继续采用ELISA技术研究冈比亚按蚊的感染情况。总之,该地区冈比亚按蚊传播疟疾的情况非常低。