Tchouakui Magellan, Fossog Billy Tene, Ngannang Brigitte Vanessa, Djonabaye Doumani, Tchapga Williams, Njiokou Flobert, Wondji Charles S
Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, Yaoundé, P.O. Box 812, Cameroon.
Department of Medical Entomology, Centre for Research in Infectious Diseases, Younde, 13591, Cameroon.
Wellcome Open Res. 2019 Mar 21;4:13. doi: 10.12688/wellcomeopenres.15013.2. eCollection 2019.
Metabolic resistance is a serious challenge to current insecticide-based interventions. The extent to which it affects natural populations of mosquitoes including their reproduction ability remains uncharacterised. Here, we investigated the potential impact of the glutathione S-transferase L119F-GSTe2 resistance on the mating competitiveness of male , in Cameroon. Swarms and indoor resting collections took place in March, 2018 in Tibati, Cameroon. WHO tube and cone assays were performed on F mosquitoes from indoor collected females to assess the susceptibility profile of malaria vectors. Mosquitoes mated and unmated males collected in the swarms were genotyped for the L119F metabolic marker to assess its association with mating male competitiveness. : Susceptibility and synergist assays, showed that this population was multiple resistant to pyrethroids, DDT and carbamates, likely driven by metabolic resistance mechanisms. Cone assays revealed a reduced efficacy of standard pyrethroid-nets (Olyset and PermaNet 2.0) with low mortality (<25%) whereas synergist PBO-Nets (Olyset Plus and PermaNet 3.0) retained greater efficacy with higher mortality (>80%). The L119F-GSTe2 mutation, conferring pyrethroid/DDT resistance, was detected in this population at a frequency of 28.8%. In addition, a total of 15 mating swarms were identified and 21 couples were isolated from those swarms. A comparative genotyping of the L119F-GSTe2 mutation between mated and unmated males revealed that heterozygote males 119L/F-RS were less able to mate than homozygote susceptible (OR=7.2, P<0.0001). Surprisingly, heterozygote mosquitoes were also less able to mate than homozygote resistant (OR=4.2, P=0.010) suggesting the presence of a heterozygote disadvantage effect. Overall, mosquitoes bearing the L119-S susceptible allele were significantly more able to mate than those with 119F-R resistant allele (OR=2.1, P=0.03). This study provides preliminary evidences that metabolic resistance potentially exerts a fitness cost on mating competiveness in resistant mosquitoes.
代谢抗性是当前基于杀虫剂的防治措施面临的严峻挑战。其对包括蚊子繁殖能力在内的自然种群的影响程度仍未明确。在此，我们在喀麦隆研究了谷胱甘肽S - 转移酶L119F - GSTe2抗性对雄性蚊子交配竞争力的潜在影响。2018年3月在喀麦隆的蒂巴蒂进行了蚊群和室内静息采集。对从室内采集的雌蚊所产的F代蚊子进行了世卫组织试管和锥形试验，以评估疟疾病媒的易感性特征。对在蚊群中采集的已交配和未交配的雄性蚊子进行L119F代谢标记基因分型，以评估其与交配雄性竞争力的关联。结果表明：易感性和增效剂试验显示，该种群对拟除虫菊酯、滴滴涕和氨基甲酸酯具有多重抗性，可能是由代谢抗性机制驱动的。锥形试验表明，标准拟除虫菊酯蚊帐（Olyset和PermaNet 2.0）的效果降低，死亡率较低（<25%），而增效剂PBO蚊帐（Olyset Plus和PermaNet 3.0）的效果更好，死亡率更高（>80%）。在该种群中检测到赋予拟除虫菊酯/滴滴涕抗性的L119F - GSTe2突变，频率为28.8%。此外，共识别出15个交配蚊群，并从这些蚊群中分离出21对蚊子。对已交配和未交配雄性蚊子的L119F - GSTe2突变进行比较基因分型发现，杂合子雄性119L/F - RS比纯合子易感雄性交配能力更弱（OR = 7.2，P < 0.0001）。令人惊讶的是，杂合子蚊子比纯合子抗性蚊子交配能力也更弱（OR = 4.2，P = 0.010），表明存在杂合子劣势效应。总体而言，携带L119 - S易感等位基因的蚊子比携带119F - R抗性等位基因的蚊子交配能力明显更强（OR = 2.1，P = 0.03）。这项研究提供了初步证据，表明代谢抗性可能对抗性蚊子的交配竞争力产生适应性代价。
