The malaria pathogen becomes resistant to the drugs used to treat the disease

BarcelonaMalaria is one of the most contagious diseases in the world. There are more than 200 million cases and up to half a million deaths each year, the vast majority of them children. Despite these numbers, little is said about them because developed countries have managed to eliminate them for decades and are now only endemic to central Africa and, to a lesser extent, Southeast Asia. Fortunately, there are effective treatments that prevent higher mortality rates. However, a recent study found that resistance to the main drugs used for treatment is spreading across Africa, which could make fighting the disease even more difficult.

Malaria is caused by a parasite called Plasmodium, which is transmitted by mosquitoes of the genus by the bite of females anopheles. Once in the blood, the plasmids go to the liver, where they multiply and then infect the red blood cells. Within these cells, the parasites multiply so strongly that they burst and are then released into the circulation. The process creates a range of symptoms, including high fever peaks (with chills and sweating), pain, and vomiting. Serious respiratory problems occur in a quarter of cases, and complications include encephalopathies and kidney problems, which can be fatal, especially in children under five.

Treating malaria before it gets complicated is effective 90% of the time. It is based on a family of drugs, artemisinin derivatives, made from a Chinese plant. Dr. Tu Youyou discovered her in the 1970s, for which she received the Nobel Prize in 2015. Current treatments usually include a derivative of artemisinin and another classic drug to reduce the chances of dangerous mutations sustaining (if one parasite is resistant to one drug, it probably won’t be resistant to the other). One of these “booster” antimalarial drugs is chloroquine, the drug that was believed to slow the rate of SARS-CoV-2 at the onset of the Covid-19 pandemic.

The discovery of artemisinin changed the prognosis of the disease as it is the most effective known drug against Plasmodium. In addition, since the 1950s, the parasite was found to have developed resistance to traditional antimalarials, which hampered their effectiveness. It was feared that this would end with artemisinin as well, as all microbes develop resistance over time.

Indeed, at the turn of the century, Cambodia began to show signs of resistance to this family of drugs. Over the next decade, they spread across Southeast Asia. Almost ten years ago, mutations of the malaria parasite were discovered in Rwanda, which led to the suspicion that it is becoming resistant to artemisinin in Africa too. This was of particular concern as more than 90% of malaria cases occur on this continent.

Resistance is advancing

Unfortunately, the effects of these mutations have now been confirmed. According to a study published in the journal a few weeks ago New England Journal of Medicine and under the direction of Dr. Toshihiro Mita, these plasmodium mutations are already so widespread in Africa that a certain loss of effectiveness of the most widespread antimalarials can be noticed. The clinical study shows that 14 of the 240 patients treated showed resistance to artemisinin and 20% of the analyzed plasmids had mutations related to this resistance. While the data has all triggered the alarms, the danger is not yet immediate: the study also found that the drugs are still working even though they take longer to cure infections.

With this in mind, one now hopes for the first malaria vaccine RTS, S, approved by the European Medicines Agency in 2015 million people). The results were so positive that a few weeks ago the WHO granted final approval of the vaccine, which is to be administered in all endemic areas. The problem is that RTS, S has very little potency (it only provides protection between 30 and 40% of those vaccinated), below the 50% threshold normally required for approval. With no better alternatives (not even in the medium term) and drug resistance increasing, it is considered the best weapon to reduce the impact of malaria on the world.

As with all infectious diseases, it is very important not to break the cycle of discovery and manufacture of treatments that fail in malaria. It’s not the only disease, drug-resistant tuberculosis is also one of the greatest threats to global health. In parallel with the development of vaccines, we must constantly invest in the search for antimicrobial drugs if we are to prevent the infections that we have more or less controlled from reoccurring strongly.

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