Pyrethroid insecticides maintain repellent effect on knock-down resistant populations of Aedes aegypti mosquitoes

Abstract

Pyrethroid-treated clothing is commonly worn for protection against mosquitoes; pyrethroids are both insecticides and repellents. Pyrethroid resistance has become increasingly common in Aedes aegypti, the vector of dengue, Zika, and other arboviruses, but it is not clear whether resistance is associated with reductions in repellency. In order to determine whether long-lasting permethrin impregnated (LLPI) clothing is protective, we used Aedes aegypti from New Orleans, LA (pyrethroid-sensitive) and San Juan, PR (resistant) to measure both lethality and repellency. PCR and Sanger sequencing were used to confirm resistance status by detecting mutations in the kdr gene at positions 1016 and 1534. Arm-in-cage trials of 100 Aedes aegypti females from both populations were performed for 10 minutes to bare arm or an arm clothed in untreated military camouflage or military camouflage impregnated with deltamethrin, permethrin, or etofenprox. Trials were repeated 4–5 times on different days. Number of landings, number of blood meals, and immediate and 24-hour mortality were recorded. Mortality was extremely low in all trials. Compared to untreated cloth, mosquitoes demonstrated a trend towards a 2%-63% reduction in landings and a statistically significant 78–100% reduction in blood feeding on pyrethroid-treated cloth for most insecticides. Effects were observed in both pyrethroid-sensitive and pyrethroid-resistant mosquito populations. Our data show that kdr mutations are associated with pyrethroid resistance but are likely not the only contributors. Pyrethroids appear to maintain repellent effect against resistant mosquitoes. This finding suggests that even in places where pyrethroid resistance is widespread, permethrin still has a role for use as a repellent on clothing to protect against mosquito bites.

Reduced effectiveness of repellents in a pyrethroid‐resistant strain of Aedes aegypti (Diptera: culicidae) and its correlation with olfactory sensitivity

“…This result is similar to the lower repellency resistance observed in the PR strain to transfluthrin compared to metofluthrin observed in the present study. In contrast to these findings, a recent paper by Bowman et al . found that a Puerto Rico strain of Ae.…”

“…32 This result is similar to the lower repellency resistance observed in the PR strain to transfluthrin compared to metofluthrin observed in the present study. In contrast to these findings, a recent paper by Bowman et al 22 found that a Puerto Rico strain of Ae. aegypti similar to the one used here carried kdr mutations, but showed no cross-resistance to repellency in arm-biting tests with permethrin, wileyonlinelibrary.com/journal/ps deltamethrin, and etofenprox, compounds acting via contact irritancy and not spatial repellency.…”

“…A recent study by Bowman et al ., however, reported that pyrethroids maintained their repellent properties in knockdown resistant populations of Ae. aegypti mosquitoes from San Juan, Puerto Rico that showed high resistance when measured as mortality …”

“…aegypti mosquitoes from San Juan, Puerto Rico that showed high resistance when measured as mortality. 22 In related studies, Mengoni and Alzogaray claimed that two deltamethrin-resistant strains of German cockroach, Blattella germanica (L.) (Blattodea: Blattellidae), had decreased sensitivity to N,N-diethyl-3-methylbenzamide (DEET) and ethyl 3-[acetyl(butyl)amino] propanoate (IR3535). 23 According to their statistical analysis, both strains had reduced responses to IR3535, while only one strain showed about 2-fold resistance to DEET, even though both strains were highly resistant to deltamethrin (RR > 677).…”

High level of resistance in the mosquito Anopheles arabiensis to pyrethroid insecticides from low malaria transmission zone of Moroto district, Karamoja region, Uganda: Implication for malaria vector control

“…This translates into about 33 % disease prevalence and may be linked to factors such as pyrethroid resistance that might be impeding efficacy of the LLINs Pyrethroids exert their insecticidal effect on the voltage-gated sodium channel (VGSC) located on the membrane of neurons [14]. When pyrethroids bind an open channel, they block its closure, thus extending the action potential and resulting in the insect's rapid paralysis, a phenomenon known as "knockdown" (kdr) [15]. However, mosquito resistance to pyrethroids is an emerging challenge to efficacy of otherwise successful insecticide-treated nets (ITN) based malaria control intervention against adult vector [16].…”