Fogging has unintended effect: Insecticide-resistant Aedes mosquitoes, warn experts

Malay Mail
Malay Mail

KUALA LUMPUR, Jan 2 — Two species of dengue virus mosquitoes — Aedes aegypti and Aedes albopictus — have recently been found to have developed a stronger resistance to insecticides, said researchers.

They said this added resistance contributes to the risk of a widespread dengue outbreak and must be taken into account when designing new measures to control mosquito populations and curb dengue fever.

“Genetic mutations in these mosquitoes in response to the widespread use of insecticides are likely the cause (of their heightened resistance),” epidemiologist and health informatician Professor Datuk Awang Bulgiba Awang Mahmud of Universiti Malaya was quoted as saying in the New Straits Times.

According to the report, a 2022 study in medical journal Parasites & Vectors confirmed that Aedes aegypti mosquitoes were highly resistant to current insecticides, while a 2021 paper in PLOS Neglected Tropical Diseases found that Senegal’s Aedes aegypti population had a high metabolic resistance to widely used insecticides.

“It is only natural for simple creatures like insects, such as mosquitoes, to evolve and adapt to a changing environment.

“For Aedes mosquitoes, this changing environment is mainly due to urbanisation and climate change. They have adapted to breed in discarded containers, small puddles of clean water, gutters and clogged drains in urban settings,” environmental health expert Professor Jamal Hisham Hashim was quoted as saying.

The researchers agreed that spraying fine insecticide is only an ineffective, short-term measure against the spread of dengue virus as it does not affect the mosquitoes’ breeding sites and larvae.

“Mosquito fogging has always been a short-term measure which targets only adult mosquitoes.

“It does not get rid of the larvae, nor does it get rid of mosquito breeding sites. So, while it does have its benefits, this is unsustainable nor an effective long-term vector-control strategy,” Awang Bulgiba said.

Meanwhile, former deputy health director-general and epidemiologist Professor Datuk Lokman Hakim Sulaiman was quoted as saying that while some dengue virus mosquitoes might die from fogging, there is “no evidence that fogging works”.

“I never believed that fogging was cost-effective. During my time (in office), I had even reduced fogging to once from twice for each reported case.

“To me, we continue doing it because it is the politically correct thing to do,” he said.

Studies have also shown that in addition to the adult mosquitoes, fogging with insecticide also unintentionally kills other insects and harms animals in the area.