[Reading Science] Discovered Microorganism That Controls Malaria Causing 500,000 Annual Deaths

US National Institutes of Health Research Team Identifies Bacteria That Capture Malaria Parasites

Malaria is a major infectious disease that causes more than 500,000 deaths worldwide each year. It is especially deadly to children under the age of five. However, scientists have attracted attention by developing a new weapon to fight malaria using microorganisms.

The U.S. National Institutes of Health (NIH) published experimental results containing this information in the international academic journal Science on the 3rd (local time). The study reported that feeding mosquitoes with bacteria found in nature had the effect of eradicating malaria parasites (Plasmodium parasites).

Efforts to prevent various infectious diseases transmitted by mosquitoes using bacteria have existed before. The bacteria Wolbachia pipientis, which counteracts viruses, is already being used in some countries to prevent dengue fever. Bacteria have also been utilized to block malaria parasites. The problem was that these bacteria were created through genetic modification, which involved technology and costs, as well as considerable public resistance, making widespread adoption difficult.

The research team accidentally discovered bacteria that can suppress malaria parasites without genetic modification by humans. Researchers from the global pharmaceutical company GlaxoSmithKline, participating in the study using mosquitoes for malaria control, noticed that some mosquitoes were becoming increasingly resistant to malaria parasite infection.

Upon closer examination, the team confirmed that this phenomenon occurred because the mosquitoes were infected with an unexpected specific bacterium. They later identified this bacterium as Delftia tsuruhatensis TC1. This bacterium is found not only in the intestines of mosquitoes and some insects but also in water, soil, and hospital-acquired infections.

The researchers found that feeding this bacterium to mosquitoes inhibited the growth of malaria parasites while they were still in the mosquito’s gut before migrating to the salivary glands. Mosquitoes harboring this bacterium had over 75% fewer malaria parasite eggs compared to those without it. The effect was also confirmed in experiments with mice. While mice bitten by normal mosquitoes were 100% infected with malaria, only one-third of mice bitten by mosquitoes carrying this bacterium contracted malaria.

The specific mechanism of action was also revealed. This bacterium secretes Harman, a plant compound used as a traditional remedy in some cultures, which attacks the malaria-causing parasites. The research team confirmed that feeding mosquitoes this substance or having them walk on it disrupted parasite development. This suggests that Harman could potentially be used as a malaria control drug.

Field experiments in natural environments were also successful. In Burkina Faso, mosquito nets about 5 to 10 meters wide were set up around areas where plants were growing, and cotton soaked with sugar and this bacterium was fed to mosquitoes. Within one night, about three-quarters of the mosquitoes were infected with the bacterium. The team then fed these mosquitoes blood from people infected with malaria and confirmed that, as in the laboratory, the bacteria blocked the growth of malaria parasites.

A representative of the research team explained, "These results could be an effective means of malaria control," adding, "The bacteria inside the mosquitoes continuously block malaria parasites without affecting their reproduction."