In the current hunt for more effective weapons against malaria, international researchers said on Thursday they were studying the pathway that has so far been little explored – killing parasites in the liver before the disease.
"It is very difficult to work on the liver stage," says Elizabeth Winkler, professor of pharmacology and drug discovery at California University in California.
"We have traditionally looked for medicines that will cure malaria," she told AFP.
For the latest research published in the journal Science, scientists have split hundreds of thousands of mosquitoes to remove parasites in them.
Each parasite was then isolated in a tube and treated with another compound – a total of 500,000 experiments.
Researchers find that some molecules have succeeded in killing the parasites.
After about six years of work, 631 candidate molecules have been identified for a "chemical vaccine" – a normal vaccine that will allow the body to make antibodies.
"If you can find a drug that you give in one day at the same time, it will kill all parasites of malaria in the face both in the liver and in the blood and lasts for three to six months. there is no such medication right now, "says Larry Slutzker, leader of the PATH Malaria and Negative Tropical Diseases (PAD) program.
Reducing the number of doses is crucial.
This is because many drugs available today should be taken for three days, said David Reddy, CEO of Medicines for Malaria Ventures.
But often, after the first dose, the child begins to feel better and the fever decreases. Thereafter, the parents retain the remaining two doses in case another of their children becomes ill.
"This has two effects: First, the child is not treated properly, and secondly it builds up drug resistance," said Reddy.
The disease develops
Malaria is caused by a miniature parasite called Plasmodium.
Female mosquitoes transmit the parasite when they bite people for food from blood (men do not bite).
Then the parasite is in the liver and multiplied. Within a few weeks, the population explodes and the parasites break down in the blood.
At this stage, fever, headache and muscle pain begin, followed by cold sweating and trembling. No treatment, anemia, breathing difficulties and even death may follow, in the case of Plasmodium falciparum, which is dominant in Africa.
The study, published Thursday, offers a "promising path, as long as it lasts several months," said Jean Gaugard, professor of public health at the University of Marseilles.
Gautthart said that new approaches are needed as resistance is growing in Asia against the most effective treatment using artemisin from a Chinese plant.
"We really need new connections," he said.
Researchers now have to confirm which of the 631 molecules identified have a real shot at destroying this global disaster.
The World Health Organization said last year that global efforts to fight malaria hit the plateau, with two million cases of the killer disease in 2017 – 219 million – compared to the previous year.
Malaria killed 435,000 people last year, most of them children under five in Africa.
The first vaccine against malaria for children – called RTS, S – will be spread in African countries in 2019, although it only reduces the risk of malaria by 40% after four doses.
Although billions of dollars have been spent, the world has not yet found a real effective solution to malaria.