Kenya Medical Research Institute (KEMRI), Centre for Geographic Medicine Research Coast, P,O, Box 42880108, Kilifi, Kenya.
Parasit Vectors. 2013 Apr 20;6:114. doi: 10.1186/1756-3305-6-114.
The scaling up of malaria vector control efforts in Africa has resulted in changing the malaria vectorial systems across different ecological settings. In view of the ongoing trends in vector population dynamics, abundance, species composition and parasite infectiousness, there is a need to understand vector distribution and their contribution to malaria transmission to facilitate future planning of control strategies. We studied indoor and outdoor malaria transmission dynamics and vector population variability of Anopheles mosquitoes in Taveta district along the Kenyan Coast.
Anopheles mosquitoes were collected indoors and outdoors in 4 ecologically different villages using CDC light traps (both indoor and outdoor) and aspiration method (day resting indoors; DRI) methods. Mosquitoes were examined for infection with P. falciparum sporozoites and blood feeding preferences using enzyme linked immunosorbent assay (ELISA). The An. gambiae and An. funestus complexes were identified by PCR technique to determine the sibling species composition.
A total of 4,004 Anopheles mosquitoes were collected consisting of 34.9%% (n = 1,397) An. gambiae s.1., 28.1% (n = 1,124) An. funestus s.l., 33.5% (n = 1,340) An. coustani and 3.6% (n = 143) An. pharoensis. A total of 14,654 culicine mosquitoes were collected, mainly Cx. quinquefasciatus. Of the total Anopheles collected, 3,729 were tested for P. falciparum sporozoite infection. The sporozoite transmission was found to be occurring both indoors and outdoors. The overall sporozoite infectivity was 0.68% (n = 2,486) indoors and 1.29% (n = 1,243) outdoors. Indoor and outdoor sporozoite infectivity and the vectorial systems varied across the 4 ecological villages. Entomological inoculation rates for the 4 villages indicate that there was site-to-site variation. In the 4 villages, Mwarusa had the highest EIRs with An. arabiensis, An. funestus and An. coustani contributing to 23.91, 11.96 and 23.91 infectious bites per person per year ib/p/year respectively. In Kiwalwa and Njoro outdoor EIR was significantly higher than indoors.
This study shows that malaria transmission is occurring both indoors and outdoors. The main vectors are An. arabiensis, An. funestus and An. coustani indoors while An. coustani is playing a major role in outdoor transmission. Effective malaria control programmes, should therefore include tools that target both indoor and outdoor transmission.
非洲疟疾媒介控制工作的扩大导致不同生态环境中的疟疾媒介系统发生变化。鉴于当前媒介种群动态、丰度、物种组成和寄生虫感染力的趋势，有必要了解媒介的分布及其对疟疾传播的贡献，以促进未来控制策略的规划。我们研究了肯尼亚沿海塔韦塔地区室内外疟疾传播动态和按蚊种群变异性。
使用 CDC 诱蚊灯（室内外）和吸蚊法（白天室内休息；DRI）在 4 个生态环境不同的村庄室内外收集按蚊。用酶联免疫吸附试验（ELISA）检测疟原虫孢子感染和血液摄食偏好。通过 PCR 技术鉴定冈比亚按蚊和芬按蚊复合体，以确定姐妹种组成。
共收集 4004 只按蚊，其中 34.9%（n=1397）为冈比亚按蚊 s.1.，28.1%（n=1124）为芬按蚊 s.l.，33.5%（n=1340）为库蚊，3.6%（n=143）为 pharoensis。共收集 14654 只库蚊，主要为 Cx. quinquefasciatus。在所收集的总按蚊中，有 3729 只为检测疟原虫孢子感染。发现室内外均有孢子传播。总孢子感染率为 0.68%（n=2486），室内为 1.29%（n=1243）。4 个生态村的室内外孢子感染力和媒介系统各不相同。4 个村庄的昆虫学接种率表明存在站点间的差异。在这 4 个村庄中，姆瓦鲁萨的 EIRs 最高，阿拉伯按蚊、芬按蚊和库蚊分别造成 23.91、11.96 和 23.91 人/年的感染性叮咬。在 Kiwalwa 和 Njoro，户外 EIR 明显高于室内。
本研究表明疟疾的传播既发生在室内也发生在室外。主要的媒介是室内的阿拉伯按蚊、芬按蚊和库蚊，而库蚊在室外传播中起着主要作用。因此，有效的疟疾控制计划应包括针对室内外传播的工具。
