Ridl Frances C, Bass Chris, Torrez Miguel, Govender Dayanandan, Ramdeen Varsha, Yellot Lee, Edu Amado Edjang, Schwabe Christopher, Mohloai Peter, Maharaj Rajendra, Kleinschmidt Immo
Malaria Research Lead Programme, Medical Research Council, Durban, South Africa.
Malar J. 2008 Sep 29;7:194. doi: 10.1186/1475-2875-7-194.
Following the success of the malaria control intervention on the island of Bioko, malaria control by the use of indoor residual spraying (IRS) and long-lasting insecticide-treated nets (LLITN) was extended to Rio Muni, on the mainland part of Equatorial Guinea. This manuscript reports on the malaria vectors present and the incidence of insecticide resistant alleles prior to the onset of the programme.
Anopheles mosquitoes were captured daily using window traps at 30 sentinel sites in Rio Muni, from December 2006 to July 2007. The mosquitoes were identified to species and their sporozoite rates, knockdown resistance (kdr) and acetylcholinesterase (AChE) sensitivity measured, to define the role of vector species in malaria transmission and their potential susceptibility to insecticides.
A total of 6,162 Anopheles mosquitoes were collected of which 4,808 were morphologically identified as Anopheles gambiae s.l., 120 Anopheles funestus, 1,069 Anopheles moucheti, and 165 Anopheles nili s.l.. Both M and S molecular forms of Anopheles gambiae s.s. and Anopheles melas were identified. Anopheles ovengensis and Anopheles carnevalei were the only two members of the An. nili group to be identified. Using the species-specific sporozoite rates and the average number of mosquitoes per night, the number of infective mosquitoes per trap per 100 nights for each species complex was calculated as a measure of transmission risk. Both kdr-w and kdr-e alleles were present in the S-form of An. gambiae s.s. (59% and 19% respectively) and at much lower frequencies in the M-form (9.7% and 1.8% respectively). The kdr-w and kdr-e alleles co-occurred in 103 S-form and 1 M-form specimens. No insensitive AChE was detected.
Anopheles gambiae s.s, a member of the Anopheles gambiae complex was shown to be the major vector in Rio Muni with the other three groups playing a relatively minor role in transmission. The demonstration of a high frequency of kdr alleles in mosquito populations before the onset of a malaria control programme shows that continuous entomological surveillance including resistance monitoring will be of critical importance to ensure the chosen insecticide remains effective.
在比奥科岛疟疾控制干预措施取得成功之后，使用室内滞留喷洒（IRS）和长效驱虫蚊帐（LLITN）进行的疟疾控制工作扩展到了赤道几内亚大陆部分的里奥木尼。本手稿报告了该项目启动前当地存在的疟疾病媒以及杀虫剂抗性等位基因的发生率。
2006年12月至2007年7月期间，在里奥木尼的30个哨点每天使用窗式诱捕器捕获按蚊。对捕获的蚊子进行种类鉴定，并测量其孢子体率、击倒抗性（kdr）和乙酰胆碱酯酶（AChE）敏感性，以确定病媒种类在疟疾传播中的作用及其对杀虫剂的潜在敏感性。
共收集到6162只按蚊，其中4808只在形态上被鉴定为冈比亚按蚊复合种，120只为富氏按蚊，1069只为穆氏按蚊，165只为尼罗按蚊复合种。鉴定出了冈比亚按蚊指名亚种和梅拉斯按蚊的M和S分子型。奥温按蚊和卡氏按蚊是尼罗按蚊复合种中仅有的两个被鉴定的成员。利用特定种类的孢子体率和每晚平均蚊子数量，计算每个种类复合体每100夜每个诱捕器中感染性蚊子的数量，以此作为传播风险的衡量指标。kdr-w和kdr-e等位基因在冈比亚按蚊指名亚种的S型中均有出现（分别为59%和19%），在M型中的频率则低得多（分别为9.7%和1.8%）。kdr-w和kdr-e等位基因在103个S型和1个M型标本中共存。未检测到不敏感的AChE。
冈比亚按蚊指名亚种，即冈比亚按蚊复合种的一个成员，被证明是里奥木尼的主要病媒，其他三个群体在传播中起相对较小的作用。在疟疾控制项目启动前，蚊子种群中kdr等位基因的高频率表明，持续的昆虫学监测，包括抗性监测，对于确保所选杀虫剂保持有效性至关重要。
