Background: Insecticides used in vector control mostly rely on vectors being exposed through contact with treated surfaces, yet little is known about the amount picked up by the insect. Measuring this amount is relevant not only for determining the actual doses that are lethal to the mosquito, but also for understanding effects on the physiology and vector competence of mosquitoes. Insecticides at sub-lethal doses can affect both parasites developing inside mosquitoes and mosquito microbiota, hence it is important to understand the processes by which parasites are exposed to insecticide inside the insect. These doses will inevitably depend on the amount of insecticide that mosquitoes pick up when they come into contact with treated nets. Methods: Three to five days old non-blood fed female Anopheles coluzzii mosquitoes were exposed to a long-lasting insecticidal net (PermaNet 2.0 containing 55 mg/m² deltamethrin), using a wire ball frame, for 0.5-5.0 minutes. Our in-house developed colorimetric test was used to visually detect the amount of deltamethrin on different parts of the mosquito (legs, heads, thoraxes, abdomens) following exposure to the net. The amount of insecticide picked up by mosquitoes from the net over a range of exposure times was measured using a high-performance liquid chromatography with diode array detection (HPLC-DAD). Results: The colorimetric test, designed to only detect the type 2 pyrethroids (i.e deltamethrin, α-cypermethrin and λ-cyhalothrin) on fabrics (e.g. ITNs) and sprayed walls, was successfully used for the first time to detect deltamethrin on mosquitoes following exposure to the net. The confirmatory HPLC-DAD analysis determined that after 2 min exposure up to 12 ng of deltamethrin adhered to mosquitoes following exposure to PermaNet 2.0 (mean = 5.2 ng/mosquito, SE = 1.9) and that the final dose depends on the length of exposure time. Conclusions: This study demonstrated the potential of a screening (type 2 pyrethroid colorimetric test) and a confirmatory test (HPLC-DAD) to determine the amount of insecticide that adheres to mosquitoes on contact with treated surfaces. This has implications for a precise lethal dose determination and detection of specific insecticide that causes the greatest mosquito mortality in circumstances where mixtures of insecticides may be used to maximise effectiveness of interventions.

中文翻译：

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测定蚊子从处理过的蚊帐中吸收的杀虫剂数量

背景：用于媒介控制的杀虫剂主要依赖于通过与处理过的表面接触而暴露的媒介，但对昆虫吸收的量知之甚少。测量该量不仅与确定对蚊子致死的实际剂量有关，而且与了解对蚊子的生理和媒介能力的影响有关。亚致死剂量的杀虫剂可同时影响蚊子内部发育的寄生虫和蚊子微生物群，因此了解寄生虫暴露于昆虫内部的杀虫剂的过程非常重要。这些剂量不可避免地取决于蚊子与处理过的蚊帐接触时吸收的杀虫剂的量。方法：三到五天大的非血液喂养雌性按蚊蚊子暴露于持久的杀虫网（含55 mg / m ^2的PermaNet 2.0溴氰菊酯），使用金属丝球框架放置0.5-5.0分钟。我们内部研发的比色法用于肉眼观察蚊帐不同部位（腿，头，胸部，腹部）的溴氰菊酯含量。使用带有二极管阵列检测（HPLC-DAD）的高效液相色谱法，在一定的暴露时间范围内，蚊子从网上吸走的杀虫剂的量进行了测量。结果：比色法设计用于仅检测织物（例如ITN）和喷涂墙壁上的2型拟除虫菊酯（即溴氰菊酯，α-氯氰菊酯和λ-氯氟氰菊酯），首次成功用于暴露后蚊子上的溴氰菊酯的检测。到网上。验证性HPLC-DAD分析确定，在暴露2分钟后，暴露于PermaNet 2.0后高达12 ng溴氰菊酯附着在蚊子上（平均= 5.2 ng /蚊，SE = 1.9），最终剂量取决于暴露时间的长短。结论：这项研究证明了筛查（2型拟除虫菊酯比色法）和确证试验（HPLC-DAD）的潜力，可确定粘附在蚊子上的杀虫剂在与被处理表面接触时的数量。这对于精确的致死剂量测定和特定杀虫剂的检测具有重要意义，在杀虫剂混合物可用于最大程度地提高干预效果的情况下，该杀虫剂可导致最大的蚊子死亡率。9），最终剂量取决于暴露时间的长短。结论：这项研究证明了筛查（2型拟除虫菊酯比色法）和确证试验（HPLC-DAD）的潜力，可确定粘附在蚊子上的杀虫剂在与被处理表面接触时的数量。这对于精确的致死剂量测定和特定杀虫剂的检测具有重要意义，在杀虫剂混合物可用于最大程度地提高干预效果的情况下，该杀虫剂可导致最大的蚊子死亡率。9），最终剂量取决于暴露时间的长短。结论：这项研究证明了筛查（2型拟除虫菊酯比色法）和确证试验（HPLC-DAD）的潜力，可确定粘附在蚊子上的杀虫剂在与被处理表面接触时的数量。这对于精确的致死剂量测定和特定杀虫剂的检测具有重要意义，在杀虫剂混合物可用于最大程度地提高干预效果的情况下，该杀虫剂可导致最大的蚊子死亡率。