SA scientists have found that perfume holds the answer to the growing threat of outdoor mosquito-repellent resistance.
They created a mixture that is a negative pseudo-azeotrope, which is used in perfumes because it retain the same composition in vapour and liquid states. It also evaporates slowly, making it long-lasting on skin.
“We took nonanoic acid – a compound which is used as an additive in the food industry – and added it to a compound used in most repellents: ethyl butylacetylaminopropionate, more commonly known as IR3535,” lead scientist Walter Focke, a professor at the department of chemical engineering, wrote in The Conversation.
The scientists tested the formula on a volunteer’s arm with 20 very hungry females of the Anopheles Arabiensis mosquito in a cup.
A second cup was placed against a person’s arm that didn’t have the repellent on it.
After three minutes they counted how many times the mosquitoes had bitten the respective arms.
The new formula not only prevented bites, but lasted up to six hours. It also killed most mosquitoes that encountered it.
The compound, the scientists say, can be developed into a commercially-viable repellent that can protect people when they are outside.
It comes in the nick of time as mosquitoes are developing resistance to topical repellents.
While tired-and-tested methods recommended by the World Health Organization, like insecticide-treated nets and indoor spraying, combat the main malaria threats indoors, they fail to treat a growing number of mosquitos species that bite people while they are outside.
Such outdoor exposure to mosquitos undermines all efforts at malaria prevention.
The most common repellent on the market is N,N-diethyl-meta-toluamide – more commonly known as DEET, which has a strong odour, high adsorption rate, an oily feel and can irritate the skin.
There were 216 million malaria cases worldwide in 2016.