Sun. Apr 21st, 2019

'Human insecticides' against malaria | Future Planet

'Human insecticides' against malaria | Future Planet

What if the people themselves poison the mosquitoes when they are stung? This is an idea that has been around the head of researchers for several years. Dozens of experiments have already been done in the laboratory that show that it could be part of the solution. It consists of taking ivermectin, a medicine that works as a poison for the insect. The volunteers, after ingesting it, fed mosquitoes in laboratories (allowing themselves to be bitten, as can be seen in the photo that accompanies this text) and it has been proven how the faculties of the insects were reduced: they lost agility, their fertility was reduced and they lived less. The mosquito dies a few hours after biting someone who has recently ingested it. Its survival will increase as more time passes after the capture, but days after it is able to limit it to about a week, which does not allow time for the malaria parasite to develop within it, so it does not transmit it. .


Sources: Science and own elaboration.

The second step is more complicated. It consists in leaving the laboratory, checking if this works in real conditions and, what is more important, measuring if the incidence of malaria goes down, since this is the ultimate goal. Last March the results of a field experiment conducted in Burkina Faso were published: more than 2,700 people participated and in the populations where they took the medication, children (who are most vulnerable to the disease) presented 20% fewer cases.

The next is to take this test to a larger scale in real conditions. It will be done by researchers from the ISGlobal de Barcelona, ​​a health institute subsidized by "la Caixa". They have obtained financing from Unitaid of 25 million dollars (just over 22 million euros) to take the experiment to Mozambican and Tanzanian populations where 100,000 people live.

The project, called Bohemia, "Tries to demonstrate that this method can be a complement, not a substitution, to mosquito nets", says Regina Rabinovich, director of the initiative for the elimination of malaria in ISGlobal. "The fight against malaria is stagnant and we have to go against it with everything we have, it is a multidisciplinary battle. With this experiment we want to know how the mosquito reacts, the impact that the drug has on different species, how we administer it to so many people, how we work with the industry to manufacture it at low cost ", adds the researcher.

It will last two years, two phases in which three doses of ivermectin (one a month) will be administered to the population (except children under five years of age and pregnant women) and it will be studied if malaria cases are reduced. "The final objective, if it is shown to be effective, would be for the World Health Organization to recommend this practice in endemic malaria areas to continue reducing the deaths caused each year," explains Carlos Chaccour, who leads the project.

In red, areas where livestock has more influence on the transmission of malaria.
In red, areas where livestock has more influence on the transmission of malaria.

In addition to people, drugs will also be given to animals. The places in Africa most plagued by malaria are typically agricultural and livestock, where the population lives very close to livestock. Some species of mosquitoes feed on animals, especially when people are protected by mosquito nets. So they become another focus of malaria transmission. Last Tuesday, these same researchers they published an investigation (see map) showing which are the places that would benefit most from medicating cattle with ivermectin to fight malaria. To do this, they have taken into account the incidence of the disease, the abundance of animals and Anopheles arabiensis, mosquitoes that tend to alternate in their diet to humans with other mammals.

In total, in addition to the 100,000 people who will participate in the study, the drug will be administered to about 12,000 pigs and cows. But the biggest challenge, from the logistical point of view, is to reach a rural population, dispersed and with some customs and culture that has nothing to do with that of researchers. The experiment is far from being limited to distributing some pills and checking the results.

The first field experiment using ivermectin to kill mosquitoes after the bite has reduced malaria by 20% in children

The ISGlobal has experience in a similar company. In 2016, a program called Maltem was implemented in Mozambique. It was very similar: it consisted of administering a drug to the population, but instead of killing the mosquito, they wanted to put an end to the malaria parasite. The idea was that if people do not carry it, for many mosquitoes that bite them, they would have nothing to transmit. The results of this study are not yet public, but Rabinovich advances that "they are promising".

Researchers already know the enormous challenges of developing a mass drug administration (DMA). The social component is almost as crucial as the scientific one. It is necessary to go from village to village, gain the trust of its inhabitants, involve locals so that most of them take a dose of this drug, which although it is a poison for mosquitoes, they have been completely safe in humans. In fact, it is used regularly to treat other endemic diseases in Africa, such as onchocerciasis and the lymphatic filariasis. "We work with 400 micrograms per kilo of weight, which marks the European label. Experiments have been carried out with larger quantities, which are more effective and also theoretically safe, but are still experimental, "explains Chaccour. With such a large population they have preferred to be conservative to avoid side effects.

The DMA will not start until January 2021. In this year and a half, the researchers have the task of getting everything ready: from the permits to the protocols of action, through the hiring of local staff.

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