Environmental Science Thematic Group, Ifakara Health Institute, PO Box 53, Ifakara, Tanzania.
Proc Biol Sci. 2013 Jan 8;280(1754):20122823. doi: 10.1098/rspb.2012.2823. Print 2013 Mar 7.
Many malaria vector mosquitoes in Africa have an extreme preference for feeding on humans. This specialization allows them to sustain much higher levels of transmission than elsewhere, but there is little understanding of the evolutionary forces that drive this behaviour. In Tanzania, we used a semi-field system to test whether the well-documented preferences of the vectors, Anopheles arabiensis and Anopheles gambiae sensu stricto (s.s.) for cattle and humans, respectively, are predicted by the fitness they obtain from host-seeking on these species relative to other available hosts. Mosquito fitness was contrasted, when humans were fully exposed and when they were protected by a typical bednet. The fitness of both vectors varied between host species. The predicted relationship between host preference and fitness was confirmed in An. arabiensis, but not in An. gambiae s.s., whose fitness was similar on humans and other mammals. Use of typical, imperfect bednets generated only minor reductions in An. gambiae s.s. feeding success and fitness on humans, but was predicted to generate a significant reduction in the lifetime reproductive success of An. arabiensis on humans relative to cows. This supports the hypothesis that such human-protective measures could additionally benefit malaria control by increasing selection for zoophily in vectors.
在非洲，许多疟疾传播媒介蚊子对吸食人类血液有极强的偏好。这种特化使它们能够维持比其他地方更高水平的传播，但对于驱动这种行为的进化力量却知之甚少。在坦桑尼亚，我们使用半野外系统来测试蚊子（按蚊属）对牛和人类的偏好是否可以通过它们从这些宿主上寻找宿主时获得的适应性来预测，这些蚊子包括阿巴蚊和冈比亚按蚊（s.s.）。当人类完全暴露和被典型蚊帐保护时，对比了蚊子的适应性。在阿巴蚊中，宿主偏好和适应性之间的预测关系得到了证实，但在冈比亚按蚊 s.s.中则没有，因为它在人类和其他哺乳动物上的适应性相似。使用典型的、不完美的蚊帐仅能略微减少冈比亚按蚊 s.s.在人类身上的取食成功率和适应性，但预计会使阿巴蚊在人类身上的终生繁殖成功率相对于牛显著降低。这支持了这样一种假设，即这种对人类的保护措施可以通过增加媒介对动物血的偏好来额外有益于疟疾控制。
