International Centre of Insect Physiology and Ecology (icipe), Nairobi, Kenya.
School of Biological Sciences, University of Nairobi, Nairobi, Kenya.
Parasit Vectors. 2018 Nov 6;11(1):577. doi: 10.1186/s13071-018-3171-3.
Most malaria vectors belong to species complexes. Sibling species often exhibit divergent behaviors dictating the measures that can be deployed effectively in their control. Despite the importance of the Anopheles funestus complex in malaria transmission in sub-Saharan Africa, sibling species have rarely been identified in the past and their vectoring potential remains understudied.
We analyzed 1149 wild-caught An. funestus (senso lato) specimens from 21 sites in Kenya, covering the major malaria endemic areas including western, central and coastal areas. Indoor and outdoor collection tools were used targeting host-seeking and resting mosquitoes. The identity of sibling species, infection with malaria Plasmodium parasites, and the host blood meal sources of engorged specimens were analyzed using PCR-based and sequencing methods.
The most abundant sibling species collected in all study sites were Anopheles funestus (59.8%) and Anopheles rivulorum (32.4%) among the 1062 successfully amplified specimens of the An. funestus complex. Proportionally, An. funestus dominated in indoor collections whilst An. rivulorum dominated in outdoor collections. Other species identified were Anopheles leesoni (4.6%), Anopheles parensis (2.4%), Anopheles vaneedeni (0.1%) and for the first time in Kenya, Anopheles longipalpis C (0.7%). Anopheles funestus had an overall Plasmodium infection rate of 9.7% (62/636), predominantly Plasmodium falciparum (59), with two infected with Plasmodium ovale and one with Plasmodium malariae. There was no difference in the infection rate between indoor and outdoor collections. Out of 344 An. rivulorum, only one carried P. falciparum. We also detected P. falciparum infection in two non-blood-fed An. longipalpis C (2/7) which is the first record for this species in Kenya. The mean human blood indices for An. funestus and An. rivulorum were 68% (93/136) and 64% (45/70), respectively, with feeding tendencies on a broad host range including humans and domestic animals such as cow, goat, sheep, chicken and pig.
Our findings underscore the importance of active surveillance through application of molecular approaches to unravel novel parasite-vector associations possibly contributed by cryptic species with important implications for effective malaria control and elimination.
大多数疟疾媒介属于种复合体。同属种通常表现出不同的行为，这决定了在控制它们时可以采取哪些有效措施。尽管在撒哈拉以南非洲，冈比亚按蚊复合体在疟疾传播中非常重要，但过去很少鉴定出同属种，其媒介潜力仍未得到充分研究。
我们分析了来自肯尼亚 21 个地点的 1149 只野生捕获的按蚊（广义）标本，这些地点涵盖了包括西部、中部和沿海地区在内的主要疟疾流行地区。使用室内和室外采集工具针对寻找宿主和休息的蚊子进行采集。使用基于 PCR 的和测序方法分析了同属种的身份、疟原虫寄生虫感染情况以及饱血标本的宿主血液来源。
在所研究的所有地点中，在成功扩增的 1062 只按蚊复合体标本中，最丰富的同属种是冈比亚按蚊（59.8%）和雷氏按蚊（32.4%）。按比例计算，冈比亚按蚊在室内采集标本中占主导地位，而雷氏按蚊在室外采集标本中占主导地位。其他鉴定出的种包括曼氏疟蚊（4.6%）、暗腹按蚊（2.4%）、须喙按蚊（0.1%），以及肯尼亚首次发现的长角按蚊 C 型（0.7%）。冈比亚按蚊的总体疟原虫感染率为 9.7%（62/636），主要是恶性疟原虫（59%），有两例感染卵形疟原虫，一例感染间日疟原虫。室内和室外采集标本的感染率没有差异。在 344 只雷氏按蚊中，只有一只携带恶性疟原虫。我们还在两只未吸血的长角按蚊 C 型（2/7）中检测到恶性疟原虫感染，这是该种在肯尼亚的首次记录。冈比亚按蚊和雷氏按蚊的平均人类血液指数分别为 68%（93/136）和 64%（45/70），它们的摄食倾向于广泛的宿主范围，包括人类和牛、山羊、绵羊、鸡和猪等家畜。
我们的发现强调了通过应用分子方法进行主动监测的重要性，这可以揭示可能由隐性种引起的新型寄生虫-媒介关联，这对有效控制和消除疟疾具有重要意义。
