Scientists propose a novel method to treat mosquitoes for Malaria control

Malaria is a mosquito-borne parasitic disease that can cause serious illness and death. It is caused by a parasite called Plasmodium and is transmitted through the bite of infected female Anopheles mosquitoes. 

Symptoms can range from mild fever, chills, and headache to severe complications like cerebral malaria, leading to seizures, coma, and death. 

Malaria parasites, which kill nearly 600,000 people a year, mostly children, are spread when female mosquitos sucking blood from a human body.

Current efforts aim to kill mosquitoes with insecticide rather than curing them of malaria.

In 2023, the World Health Organization (WHO) reported that Nigeria had the highest number of malaria deaths among all countries, with 30.9% of the deaths occurring there. Over half of the malaria deaths globally were concentrated in just four countries which were Nigeria, the Democratic Republic of the Congo, Niger, and the United Republic of Tanzania. 

The West African nation accounts for almost a third of those who die from malaria each year.

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The vaccines that were introduced, called R21/Matrix-M, are the second to be approved by the World Health Organisation (WHO) and are being given to children between five and 15 months old.

And researchers say it is 75% effective, but health experts recommend using it alongside other malaria prevention tools, such as mosquito nets and insecticides.

All the efforts to prevent the spread of the parasitic disease have played a pivotal role in reducing the number of those who are infected by the disease.

But a team at Harvard University has found a pair of drugs that can successfully rid the insects of malaria when absorbed through their legs. Coating bed nets with the drug cocktail is the long-term aim.

Sleeping under a bed net has been one of the most successful ways of preventing malaria, as the main malaria-spreading mosquitoes hunt at night. Every family member is advised by the Ministry of Health to sleep under a treated mosquito net to reduce the spread.

Vaccines to protect children living in high-risk malaria areas have also been recommended as another way of reducing the risk of being infected.

Nets are both a physical barrier and also contain insecticides that kill mosquitoes that land on them.

But mosquitoes have become resistant to insecticides in many countries, so the chemicals no longer kill the insects as effectively as they used to.

“We haven't tried to directly kill parasites in the mosquito before this, because we were just killing the mosquito,” says researcher Dr Alexandra Probst, from Harvard.

However, Dr Probst says that the approach is no longer cutting it.

The researchers had to analyse malaria's DNA to find possible weak spots while it is infecting mosquitoes.

They took a large library of potential drugs and narrowed it down to a shortlist of 22. These were tested when female mosquitoes were given a blood meal contaminated with malaria.

In their article published in a journal called Nature, the scientists describe two highly effective drugs that killed 100% of the parasites.

The drugs were tested on material similar to bed nets.

“Even if that mosquito survives contact with the bed net, the parasites within are killed, and so it's still not transmitting malaria,” said Dr Probst.

“I think this is a really exciting approach, because it's a new way of targeting mosquitoes themselves.”

She says the malaria parasite is less likely to become resistant to the drugs as there are billions of them in each infected person, but fewer than five in each mosquito.

The effect of the drugs lasts for a year on the nets, potentially making it a cheap and long-lasting alternative to insecticide, the researchers say.

This approach has been proven in the laboratory. The next stage is already planned in Ethiopia to see if the anti-malarial bed nets are effective in the real world.

It will take at least six years before all the studies are completed to know if this approach will work.

But the vision is to have bed nets treated with both anti-malaria drugs and insecticide so that if one approach doesn't work, then the other will.

In 2023, the World Health Organisation reported 263 million malaria cases and 597,000 malaria deaths worldwide. The WHO African Region continued to bear the greatest burden, accounting for approximately 94% of all malaria cases and 95% of deaths. Children under 5 years old were disproportionately affected, with 76% of global malaria deaths in this age group.