The World Health Organization, recommends the use of insecticide treated nets and indoor spraying as the main malaria vector control interventions. However, the main limitation to this is that most malaria infections in Africa, may be due to people being exposed to outdoor vectors. Thus, the current vector control measures needed to be updated to match these specific conditions.
In recent years, topical mosquito repellents have grown in popularity, since they prevent contact with the blood seeking female (anopheles mosquito) malaria vectors.
Though there are a couple of mosquito repellents available in the market, the most widely used would be N,N-diethyl-meta-toluamide – more commonly known as DEET.
While DEET has enjoyed long term popularity and effectiveness, it would appear that vectors are now beginning to develop resistance to the chemical, and consumers have also complained about it’s odour,
high adsorption rate, oily feel and the skin irritation it causes. Hence, the search for a substitute began.
Because if the rigorous nature and high cost of finding new active compounds, some scientists began to look into the viability of combining mixtures of approved repellents.
The result was a novel repellent that had a longer lifespan than commercially available repellents. It also had the added benefit of not only repelling mosquitoes but killing them too if they make contact with it.
The result of their findings produced a new compound that can be developed into a commercially viable repellent that can protect people when they are outside.
Most repellents are made up of compounds that are mixed with carrier oils. But they evaporate quickly and need to be reapplied often.
To solve this problem they proposed to create a mixture that was a negative pseudo-azeotrope just like the ones used in perfumes. A pseudo-azeotrope is a mixture of substances that retains the same composition in vapour and liquid states. In particular, a negative pseudo-azeotrope evaporates slower and this makes it last longer.
They took nonanoic acid – a compound which is used as an additive in the food industry – and added it to a compound used in most repellants: ethyl butylacetylaminopropionate, more commonly known as IR3535.
After mixing the formula, it was tested by applying it to someone’s forearm and then placing a cup with 20 hungry, female Anopheles arabiensis mosquitoes against it. A control was also set up by placing another cup with mosquitoes against a person’s arm that didn’t have the repellent on it.
After three minutes they checked to see how many times the mosquitoes had bitten the respective arms.
Results of the experiment showed that the new formula was better at repelling the mosquito throughout the three minutes and that the effect lasted for up to six hours on the skin. The result also showed that most mosquitoes that came into contact with our formula died.
The spread of malaria is dependent on a number of factors. These include how many mosquito vectors there are in a particular area, how susceptible they are to the malaria parasite, what hosts the mosquitoes are feeding off, and the survival period of the mosquito.
Two big challenges have developed that are making the elimination of malaria difficult. The first is that the vectors have started developing resistance against the main control method: insecticides. The second is that the parasite that spreads malaria Plasmodium falciparum has developed resistance to anti-malarials.
What this means is that malaria won’t be eliminated with the use of one type of control method. An integrated multi and trans-disciplinary approach is needed.
New, innovative, safe and sustainable methods need to be researched and developed to overcome current resistance trends and prevent transmission of malaria from all angles.
This research opens the door to a new mosquito repellent formulation that improves the armoury against malaria.
Source: The Conversation
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