Pesticides are used to prevent mosquito-borne diseases from spreading. Pesticide resistance has developed in mosquitos in recent decades, but it’s unclear how much of that is related to mosquito behavior.

According to a study published in Scientific Reports, female mosquitoes learn to avoid insecticides after a single exposure. Pesticides may become less effective against mosquitoes as a result, according to scientists.

To study this, Frederic Tripet and colleagues subjected female Aedes aegypti and Culex quinquefasciastus mosquitoes – which transmit dengue, Zika, and West Nile fever – to non-lethal doses of the commonly used anti-mosquito pesticides malathion, propoxur, deltamethrin, permethrin, and lambda-cyhalothrin. They then looked at whether mosquitoes were discouraged from feeding and resting after being exposed to the same pesticide, as well as whether this had an effect on mosquito survival.

The researchers found that mosquitoes that had been pre-exposed to a pesticide avoided passing through a pesticide-treated net in order to reach a food source at a higher rate than those who had not been pre-exposed.

Only 15.4% of A. aegypti and 12.1% of C. quinquefasciastus that had been pre-exposed passed through the net in order to feed, compared to 57.7% of A. aegypti and 54.4% of C. quinquefasciastus that had not been pre-exposed.

Subsequently, the survival rate of pre-exposed mosquitoes was more than double that of mosquitoes that had not been pre-exposed. 38.3% of A. aegypti and 32.1% of C. quinquefasciastus that had been pre-exposed and 11.5% of A. aegypti and 12.9% C. quinquefasciastus that had not been pre-exposed survived exposure to the pesticide-treated net.

The researchers also found that pre-exposed mosquitoes were more likely than mosquitoes that had not been pre-exposed to a pesticide to rest in a container that smelt of a control substance, rather than in a container that smelt of a pesticide.

75.7% of A. aegypti and 83.1% of C. quinquefasciastus that had been pre-exposed to a pesticide rested in the pesticide-free container, compared to 50.2% of A. aegypti and 50.4% of C. quinquefasciastus that had not been pre-exposed.

The findings suggest that mosquitoes that have been exposed to non-lethal doses of pesticides learn to avoid these pesticides and, as a result, may seek out safer food sources and resting sites, allowing them to survive to reproduce.

Source: 10.1038/s41598-022-05754-2

Image Credit: Getty

You were reading: These widely used anti-mosquito pesticides may not save you from mosquitoes bites