Scientists have discovered two parasites similar to malaria parasites affecting humans in African great apes. It would seem that this discovery is thus the solution of the century-old enigma of how malaria infected humans.
Plasmodium is the parasite that causes malaria. It is neither a virus nor a bacterium, it is more like plants. There are six species of Plasmodium that can infect humans, but there are also several that can be present in the blood of mammals, reptiles or birds. Since most Plasmodium species that can infect humans do not infect other vertebrates, the question of their origin has always been a mystery to scientists.
Outraged P. falciparum which is the most widespread and dangerous species for humans, P. malariae is the least well characterized human parasite according to an article in Nature Communications.
Different species of Plasmodium
In the 1920s, parasites similar to P. malariae have been found in the blood of chimpanzees. The same parasite had been thought to infect humans and monkeys. Later we discovered P.brasilianuma form that seemed similar, and which infected monkeys in the Americas. However, following a comparison of the DNA of P. malariae with that of the parasites found in monkeys led by the team of Dr Lindsey Plenderleith, of the University of Edinburgh, it was found that there were three distinct species. One of the species discovered, named P.celatumis a species that is not at all genetically similar to human varieties.
On the other hand, the other parasite discovered is closer to P.malariae and was nicknamed P.malariae-like. The comparison between P.malariae-like et P.malariae allowed scientists to explore genetic history. They concluded that P. malariae evolved from a parasite infecting monkeys and underwent certain genetic transformations to become very rare, probably when it began to colonize humans.
This process is very similar to what must have happened to P. falciparum when it evolved from a parasite affecting only gorillas.
P. malariae is also dangerous
Unlike other malaria parasites, P. malariae has not been studied extensively, given the mild symptoms it causes. Yet this parasite is able to persist chronically and reappear years or decades following the initial infection. P. malariae may therefore represent a greater risk to health than we think.
According to Dr Plenderleith, they hope their results can provide vital clues as to how P.malariae was able to infect humans, and also help scientists assess whether further transmission of parasites from monkeys to humans is likely. Furthermore, knowledge of other malaria parasites might help us combat the dangerous P. falciparum.
SOURCE: IFLScience