International Centre of Insect Physiology and Ecology, P.O. Box 30772-00100, Nairobi, Kenya.
University of Nairobi, P.O. Box 30197-30100, Nairobi, Kenya.
Sci Rep. 2022 May 3;12(1):7131. doi: 10.1038/s41598-022-11333-2.
Outdoor biting by anopheline mosquitoes is one of the contributors to residual malaria transmission, but the profile of vectors driving this phenomenon is not well understood. Here, we studied the bionomics and genetically characterized populations of An. gambiae and An. funestus complexes trapped outdoors in three selected dryland areas including Kerio Valley, Nguruman and Rabai in Kenya. We observed a higher abundance of Anopheles funestus group members (n = 639, 90.6%) compared to those of the An. gambiae complex (n = 66, 9.4%) with An. longipalpis C as the dominant vector species with a Plasmodium falciparum sporozoite rate (Pfsp) of 5.2% (19/362). The known malaria vectors including An. funestus s.s. (8.7%, 2/23), An. gambiae (14.3%, 2/14), An. rivulorum (14.1%, 9/64), An. arabiensis (1.9%, 1/52) occurred in low densities and displayed high Pfsp rates, which varied with the site. Additionally, six cryptic species found associated with the An. funestus group harbored Pf sporozoites (cumulative Pfsp rate = 7.2%, 13/181). We detected low frequency of resistant 119F-GSTe2 alleles in An. funestus s.s. (15.6%) and An. longipalpis C (3.1%) in Kerio Valley only. Evidence of outdoor activity, emergence of novel and divergent vectors and detection of mutations conferring metabolic resistance to pyrethroid/DDT could contribute to residual malaria transmission posing a threat to effective malaria control.
户外按蚊叮咬是残留疟疾传播的原因之一，但驱动这一现象的媒介物特征尚不清楚。在这里，我们研究了在肯尼亚三个选定的旱地地区（包括凯里谷、恩古鲁曼和拉拜）户外捕获的冈比亚按蚊和芬按蚊复合体的生物学特性，并对其进行了基因特征分析。我们观察到，与冈比亚按蚊复合体（n=66，9.4%）相比，芬按蚊组（n=639，90.6%）成员的丰度更高，其中安氏长体按蚊 C 是优势媒介，疟原虫裂殖子率（Pfsp）为 5.2%（19/362）。已知的疟疾媒介包括芬按蚊 s.s.（8.7%，2/23）、冈比亚按蚊（14.3%，2/14）、里夫按蚊（14.1%，9/64）、阿巴依蚊（1.9%，1/52），它们的密度较低，但 Pfsp 率较高，且因地点而异。此外，与芬按蚊组相关的六种隐种也携带疟原虫裂殖子（累积 Pfsp 率=7.2%，13/181）。我们仅在凯里谷检测到芬按蚊 s.s.（15.6%）和安氏长体按蚊 C（3.1%）中对 119F-GSTe2 等位基因的抗性频率较低。户外活动的证据、新型和不同的媒介的出现以及对拟除虫菊酯/DDT 代谢抗性的突变的检测都可能导致残留疟疾传播，对有效疟疾控制构成威胁。
