Killeen Gerry F, Kihonda Japhet, Lyimo Edith, Oketch Fred R, Kotas Maya E, Mathenge Evan, Schellenberg Joanna A, Lengeler Christian, Smith Thomas A, Drakeley Chris J
Ifakara Health Research and Development Centre, Box 53, Ifakara, Morogoro, United Republic of Tanzania.
BMC Infect Dis. 2006 Nov 10;6:161. doi: 10.1186/1471-2334-6-161.
African malaria vectors bite predominantly indoors at night so sleeping under an Insecticide-Treated Net (ITN) can greatly reduce malaria risk. Behavioural adaptation by mosquitoes to increasing ITN coverage could allow vector mosquitoes to bite outside of peak sleeping hours and undermine efficacy of this key malaria prevention measure.
High coverage with largely untreated nets has been achieved in the Kilombero Valley, southern Tanzania through social marketing programmes. Direct surveys of nightly biting activity by An. gambiae Giles were conducted in the area before (1997) and after (2004) implementation of ITN promotion. A novel analytical model was applied to estimate the effective protection provided by an ITN, based on published experimental hut trials combined with questionnaire surveys of human sleeping behaviour and recorded mosquito biting patterns.
An. gambiae was predominantly endophagic and nocturnal in both surveys: Approximately 90% and 80% of exposure occurred indoors and during peak sleeping hours, respectively. ITNs consistently conferred >70% protection against exposure to malaria transmission for users relative to non-users.
As ITN coverage increases, behavioural adaptation by mosquitoes remains a future possibility. The approach described allows comparison of mosquito biting patterns and ITN efficacy at multiple study sites and times. Initial results indicate ITNs remain highly effective and should remain a top-priority intervention. Combined with recently developed transmission models, this approach allows rapid, informative and cost-effective preliminary comparison of diverse control strategies in terms of protection against exposure before more costly and intensive clinical trials.
非洲疟疾传播媒介主要在夜间于室内叮咬，因此睡在经杀虫剂处理的蚊帐（ITN）下可大幅降低疟疾风险。蚊子对ITN覆盖率增加的行为适应可能使媒介蚊子在睡眠高峰期之外叮咬，从而削弱这一关键疟疾预防措施的效果。
通过社会营销项目，坦桑尼亚南部的基洛梅罗山谷已实现了用大量未经处理的蚊帐实现高覆盖率。在推广ITN之前（1997年）和之后（2004年），对该地区冈比亚按蚊的夜间叮咬活动进行了直接调查。基于已发表的实验小屋试验，结合对人类睡眠行为的问卷调查和记录的蚊子叮咬模式，应用了一种新颖的分析模型来估计ITN提供的有效保护。
在两项调查中，冈比亚按蚊主要为室内栖息和夜间活动：分别约90%和80%的接触发生在室内和睡眠高峰期。相对于未使用ITN的人，ITN始终为使用者提供>70%的保护，使其免受疟疾传播。
随着ITN覆盖率的增加，蚊子的行为适应在未来仍有可能发生。所描述的方法允许在多个研究地点和时间比较蚊子叮咬模式和ITN功效。初步结果表明，ITN仍然非常有效，应继续作为首要干预措施。结合最近开发的传播模型，这种方法能够在进行成本更高、更密集的临床试验之前，就针对暴露的保护方面，对不同控制策略进行快速、信息丰富且具有成本效益的初步比较。
