Environmental Sciences Thematic Group, Ifakara Health Institute, Ifakara, Tanzania.
Malar J. 2012 Dec 19;11:425. doi: 10.1186/1475-2875-11-425.
Host responses are important sources of selection upon the host species range of ectoparasites and phytophagous insects. However little is known about the role of host responses in defining the host species range of malaria vectors. This study aimed to estimate the relative importance of host behaviour to the feeding success and fitness of African malaria vectors, and assess its ability to predict their known host species preferences in nature.
Paired evaluations of the feeding success and fitness of African vectors Anopheles arabiensis and Anopheles gambiae sensu stricto in the presence and limitation of host behaviour were conducted in a semi-field system (SFS) at Ifakara Health Institute, Tanzania. In one set of trials, mosquitoes were released within the SFS and allowed to forage overnight on a host that was free to exhibit a natural behaviour in response to insect biting. In the other, mosquitoes were allowed to feed directly on from the skin surface of immobile hosts. The feeding success and subsequent fitness of vectors under these conditions were investigated on six host types (humans, calves, chickens, cows, dogs and goats) to assess whether physical movements of preferred host species (cattle for An. arabiensis, humans for An. gambiae s.s.) were less effective at preventing mosquito bites than those of common alternatives.
Anopheles arabiensis generally had greater feeding success when applied directly to host skin than when foraging on unrestricted hosts (in five of six host species). However, An. gambiae s.s. obtained blood meals from free and restrained hosts with similar success from most host types (four out of six). Overall, the blood meal size, oviposition rate, fecundity and post-feeding survival of mosquito vectors were significantly higher after feeding on hosts free to exhibit behaviour, than those who were immobilized during feeding trials.
Allowing hosts to move freely during exposure to mosquitoes was associated with moderate reductions in mosquito feeding success, but no detrimental impact to the subsequent fitness of mosquitoes that were able to feed upon them. This suggests that physical defensive behaviours exhibited by common host species including humans do not impose substantial fitness costs on African malaria vectors.
宿主反应是影响外寄生虫和植食性昆虫宿主范围的重要选择因素。然而，关于宿主反应在确定疟疾传播媒介宿主范围方面的作用知之甚少。本研究旨在评估宿主行为对非洲疟疾传播媒介取食成功率和适合度的相对重要性，并评估其预测已知宿主物种偏好的能力。
在坦桑尼亚伊法卡拉卫生研究所的半野外系统（SFS）中，对非洲媒介按蚊属（Anopheles arabiensis）和按蚊属（Anopheles gambiae sensu stricto）的取食成功率和适合度进行了配对评估，在有无宿主行为限制的情况下进行。在一组试验中，将蚊子释放到 SFS 中，并允许它们在一个宿主上觅食过夜，该宿主可以自由地对昆虫叮咬做出自然反应。在另一种情况下，蚊子可以直接从固定不动的宿主的皮肤表面取食。在这些条件下，对六种宿主类型（人、小牛、鸡、牛、狗和山羊）进行了蚊子的取食成功率和后续适合度的研究，以评估牛（对于 An. arabiensis）和人类（对于 An. gambiae s.s.）等首选宿主的身体运动是否比常见替代物更能有效地防止蚊子叮咬。
与在不受限制的宿主上觅食相比，当直接应用于宿主皮肤时，An. arabiensis 通常具有更高的取食成功率（在六种宿主类型中的五种中）。然而，An. gambiae s.s. 从自由和受限的宿主中获得血液餐的成功率相似，从大多数宿主类型中（六种中的四种）。总体而言，与在喂食试验中被固定的宿主相比，当暴露于可以自由移动的宿主时，蚊子的血液餐大小、产卵率、繁殖力和取食后存活率显著更高。
允许宿主在暴露于蚊子时自由移动与适度降低蚊子取食成功率相关，但对能够取食的蚊子的后续适合度没有不利影响。这表明，包括人类在内的常见宿主物种表现出的身体防御行为不会对非洲疟疾传播媒介造成实质性的适合度成本。
