Adding liquid soap can boost the potency of some of the pesticides used on malaria-carrying mosquitoes. The discovery is detailed in a study published November 17 in the journal PLOS Neglected Tropical Diseases and offers a tool in the fight against the disease.
[Related: New four-dose malaria vaccine is up to 80 percent effective.]
Malaria is most prevalent in Asia, Latin America, and sub-Saharan Africa and is caused by several species of parasites that are transmitted by the bites of infected female Anopheles mosquitoes. It causes severe fatigue, fever, headaches, and chills and can be fatal. When it is treated with the right medication, such as artemether-lumefantrine, it can be cured and the malaria parasites can be completely cleared from the body. The United States Centers for Disease Control and Prevention estimates that there were 241 million cases of malaria worldwide and 627,000 deaths in 2020.
While the first malaria vaccines were approved and recommended in 2021, the mosquitoes that carry malaria are becoming more resistant to insecticides.
“Over the past two decades, mosquitoes have become strongly resistant to most insecticides,” study co-author and University of Texas at El Paso (UTEP) evolutionary biologist Colince Kamdem said in a statement. “It’s a race now to develop alternative compounds with new modes of action.”
Before coming to UTEP, Kamdem worked at Cameroon’s Centre for Research in Infectious Diseases, where he first saw soap’s potential potency during some routine insecticide testing. A special class of insecticide called neonicotinoids have shown to be a potential alternative that targets the mosquito populations that show resistance to current insecticides. However, they can have negative effects on bees if not used carefully and neonicotinoids do not kill some mosquito species unless their potency is boosted.
World Health Organization protocols recommend adding a seed-oil based product to insecticides to test a mosquito’s susceptibility. When the compound was added, Kamdem noticed that it was more effective than when the insecticide was used on its own.
“That compound belongs to the same class of substances as kitchen soap,” Kamdem said. “We thought, ‘Why don’t we test products that have same properties?’”
The team selected three inexpensive, linseed-oil based soaps that are readily available in sub-Saharan African countries. They added the soaps to four different neonicotinoids. In every case, the potency was increased.
[Related: Mosquitoes are becoming resistant to our best defenses.]
“All three brands of soap increase mortality from 30 percent to 100 percent compared to when the insecticides were used on their own,” study co-author Ashu Fred said in a statement. Fred is a PhD student at the University of Yaoundé I in Cameroon.
They also tested a class of insecticides called pyrethroids. This class did not see the added benefits of the boost from soap. They hope to conduct additional testing to see exactly how much soap is needed to enhance insecticides.
“We would love to make a soap-insecticide formulation that can be used indoors in Africa and be healthy for users,” Kamdem said. “There are unknowns as to whether such a formulation will stick to materials like mosquito nets, but the challenge is both promising and very exciting.”
Malaria was once endemic in the US, but was eradicated by the 1970s. However, the CDC issued a health advisory in June after at least four people in Florida and one in Texas contracted homegrown cases of malaria. The disease is most common in warm climates and some scientists worry that as global temperatures continue to rise, more regions will be affected by malaria. A 2022 study published in Nature found that climate change can exacerbate a full 58 percent of the infectious diseases that humans come in contact with worldwide.
