[National Malaria Day] After malaria is eliminated, will the malarial parasite disappear from the earth?

April 26, 2024 is the 17th "National Malaria Day" and the publicity theme is "Preventing the re-transmission of malaria and continuing to consolidate the elimination results."

Malaria is one of the three major infectious diseases in the world. It has long caused great harm to human health. Eliminating malaria is the common wish of people all over the world. On June 30, 2021, the World Health Organization officially announced that my country has eliminated malaria, which is a great feat!

Q: Does malaria elimination mean that the malarial parasite has disappeared from the earth and we can rest easy?

A: The answer is no .

First, malaria elimination is regional, and no local malaria transmission has been achieved in a certain area . However, there are huge differences in the malaria epidemic situation, health facilities and economic conditions of each country, so the time process to achieve the goal of malaria elimination is different. In 2022, malaria is still prevalent in 85 countries and regions in the world. Due to cross-border personnel movement and other reasons, it still poses a serious threat to the health of people in countries and regions that have eliminated malaria.

Secondly, the elimination of malaria is aimed at the transmission of Plasmodium in the human population, and the cross-species transmission of Plasmodium in non-human primates still persists . Nearly 300 species of Plasmodium have been discovered, which can be divided into four major categories. The first category is Plasmodium that mainly parasitizes humans, including Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae and Plasmodium ovale; the second category is Plasmodium that mainly parasitizes other non-human primates, with more than 30 species; the third and fourth categories are Plasmodium that parasitize rodents and birds, respectively. Since they do not infect humans, these Plasmodium will not pose a threat to public health.

Many malaria parasites that parasitize primates are zoonotic . Plasmodium falciparum is a parasite that has successfully adapted to humans from parasitizing great apes. There are multiple reports of Plasmodium vivax and Plasmodium ovale infecting apes, monkeys, or orangutans under natural conditions. Plasmodium malariae and Plasmodium brasiliensis have been reported to infect humans naturally. Plasmodium malariae and Plasmodium brasiliensis are genetically identical and can even be considered synonyms. Plasmodium knowlesi and Plasmodium howler monkeys have adapted to develop in humans and non-human primates, and their impact on human health may even affect global strategies for malaria elimination.

All malarial parasites that infect humans are found in nonhuman primates, which in turn can serve as reservoirs for transmission to humans. In addition, new malarial parasites that infect nonhuman primates could emerge and jump to humans if some parasites acquire mutations that allow them to bind to human receptors.

It can be seen from this that Plasmodium will not disappear from the earth just because the goal of eliminating malaria is achieved. Its potential threat to people in areas where malaria has been eliminated and even to the health of all mankind will be long-term, and we must not take it lightly .

However, malaria parasites can only be spread through Anopheles mosquitoes, with which they have evolved and adapted over a long period of time. Therefore, malaria epidemics are regionally limited by the host. In non-epidemic areas and areas where malaria has been eliminated, the chance of being infected by malaria parasites is zero. At the same time, as eukaryotic single-cell microorganisms, malaria parasites mainly live in the red blood cells of warm-blooded animal hosts. Under normal circumstances, they can be identified under an ordinary optical microscope using 10 microliters of peripheral blood, and the current variety of nucleic acid detection technologies can promptly and accurately identify the parasite species, thereby achieving precision treatment.

Potential transmission of Plasmodium between humans and non-human primates

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Source: Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention