Laboratório de Mosquitos Transmissores de Hematozoários, Instituto Oswaldo Cruz, Fiocruz, Brazil.
Laboratório de Biologia Molecular de Flavivírus, Instituto Oswaldo Cruz, Fiocruz, Brazil.
Biomed Res Int. 2018 Oct 9;2018:6257860. doi: 10.1155/2018/6257860. eCollection 2018.
Chemical control is still a major strategy to constrain vector density and mitigate pathogen transmission. However, insecticide overuse poses a high selective pressure, favouring the spread of resistance alleles in natural populations. In an insecticide-free environment, a fitness cost is expected in resistant insects when compared to susceptible counterparts. This study investigates whether insecticide resistance to an organophosphate (temephos) and a pyrethroid (deltamethrin) is associated with fitness traits in four wild populations sampled every three months over one year.
We measured development time from larvae to adult, female survival, wing length, fecundity, and adult resistance to starvation in field insecticide resistant populations four times over a year. These results were confronted with resistance levels to temephos and deltamethrin and with potentially related mechanisms, including a mutation in the pyrethroid target site. No differences in fitness cost were found after contrasting mosquitoes from the same population collected throughout a year, irrespective of differences in insecticide resistance levels. Additionally, significant differences were not observed among field populations. However, compared to the reference strain Rockefeller, field females survived significantly less. Moreover, larval development was equal or slower in three out of four field populations. In no case differences were evidenced in starvation tolerance, wing length, and fecundity.
Overall, field resistant mosquitoes seemed to have a slight fitness disadvantage when compared with the Rockefeller susceptible strain which might represent a potential fitness cost of insecticide resistance. However, after comparing from the same population but sampled at different moments, or from different field populations, mosquito life-history traits varied independently of resistance ratios. The metabolic deviations necessary to overcome the adverse effects of insecticides may cause an energy trade-off that affects energy allocation and ultimately basic demands of insect biology. The extent of fitness cost due to insecticide resistance is critical information to delay the evolution of resistance in wild vector populations.
化学防治仍然是控制病媒密度和减轻病原体传播的主要策略。然而，杀虫剂的过度使用带来了很高的选择压力，有利于抗性等位基因在自然种群中的传播。在没有杀虫剂的环境中，与敏感个体相比，抗性昆虫预计会有适应性成本。本研究调查了在一年中每三个月采样一次的四个野生种群中，对有机磷（灭蚊灵）和拟除虫菊酯（溴氰菊酯）的杀虫剂抗性是否与适应性特征有关。
我们在一年中四次测量了野外抗杀虫剂种群从幼虫到成虫的发育时间、雌虫存活率、翅长、繁殖力以及对饥饿的成虫抗性。这些结果与灭蚊灵和溴氰菊酯的抗性水平以及可能相关的机制进行了对比，包括拟除虫菊酯靶标位点的突变。无论杀虫剂抗性水平如何，在同一地点全年收集的蚊子之间进行对比时，没有发现适应性成本的差异。此外，在野外种群之间也没有观察到显著差异。然而，与参考品系洛克菲勒相比，野外雌虫的存活率明显较低。此外，在四个野外种群中有三个种群的幼虫发育时间相等或更慢。在任何情况下，都没有证据表明在饥饿耐受力、翅长和繁殖力方面存在差异。
总的来说，与洛克菲勒敏感品系相比，野外抗性蚊子似乎略有适应性劣势，这可能代表了杀虫剂抗性的潜在适应性成本。然而，在比较同一地点但在不同时间采样的蚊子，或来自不同野外种群的蚊子时，蚊子的生活史特征与抗性比无关。克服杀虫剂不利影响所需的代谢偏差可能会导致能量权衡，从而影响能量分配，并最终影响昆虫生物学的基本需求。由于杀虫剂抗性导致的适应性成本的程度是延迟野生病媒种群中抗性进化的关键信息。
