25 April is World Malaria Day. As a major global infectious disease, malaria has always threatened human health and is one of the world's leading causes of death from infectious diseases.
According to WHO, there will be an estimated 241 million cases of malaria worldwide in 2020, with around 627 000 malaria deaths. Of the six regions in the world classified by WHO, africa is the most affected by malaria, accounting for 95% of the global total of malaria cases and 96% of malaria deaths in 2020. It is estimated that children under 5 years of age account for 80% of all malaria deaths in the region.
On 30 June 2021, the World Health Organization announced that the number of malaria infections in China had decreased from 30 million in the 1940s to zero, a remarkable feat that had officially been certified by WHO for malaria elimination.
Malaria is well known to be an infectious disease transmitted by Plasmodium through female Anopheles mosquitoes. Thanks to Mr. Tu's artemisinin, the global malaria mortality rate has fallen by half. However, scientists are still uncertain about how the parasite infects humans.
Recently, in a study published in Nature Communications, a team of researchers from the University of Edinburgh in the United Kingdom revealed the origin of zoonotic diseases from The African Plasmodium: about 5,000 years ago, in sub-Saharan Africa, a parasite infected with apes jumped into humans.
Six parasites of the Plasmodium genus are known to cause malaria in humans, including Plasmodium malariae and Plasmodium falciparum.
Plasmodium falciparum is the deadliest and is the cause of most malaria-related deaths. In contrast, the three-day malaria parasite usually causes only mild disease or even no disease, and often coexists with other malaria parasites in multi-species infections.
Although infection with the three-day malaria parasite may not appear to be life-threatening, if left untreated, the three-day malaria parasite may persist in the body for a long time and recur years or decades after the initial infection, or even last a lifetime.
As early as a century ago, scientists used microscopes to find that chimpanzees were infected with what appeared to be the same parasite as the three-day malaria parasite, and thought it belonged to the same species as the parasite that infected humans. But because genetic studies have not yet been conducted on the parasites in chimpanzees, this hypothesis is controversial.
In the new study, the researchers generated new sequences from DNA from feces and blood samples from wild and captive chimpanzees and gorillas infected with Plasmodium trichophyllum.
They found, in fact, that there were three different parasites of the genus Plasmodium that were once thought to be all Three-day Malaria Parasites. The three-day malaria parasite mainly infects humans; the other two parasites infect apes and gorillas, one of which is called P. celatum) is found in chimpanzees, gorillas, and bonobos in Central and West Africa, but it is only closely related to Plasmodium trichophyllum; another infected ape parasite, called P. praemariae, is more closely related to Plasmodium trichophyllum.
About 5,000 years ago, the researchers explain, the population of plasmodium infecting humans experienced a genetic bottleneck that led to a significant reduction in population size and the loss of much of the genetic variation, but that may have paved the way for the emergence of the three-day malaria parasite.
Study corresponding author Professor Paul Sharp, director of the Centre for Evolutionary Biology and Immunity, Infection and Evolution at the University of Edinburgh, said: "It appears that ape parasites cannot simply infect humans. This cross-species jump will most likely require a special mutation of the parasite, allowing it to infect humans. The first patient zero infected by mosquito bites will get only a small number of parasites, which contain only a small fraction of the genetic diversity of ape parasites, which is the bottleneck. ”
Thus, about 5,000 years ago, the three-day malaria parasite jumped from African apes into humans.
Modern humans evolved in Africa about 200,000 years ago, and out of Africa and into various parts of the world about 70,000 to 100,000 years ago.
Sharp said: "In this context, 5,000 years ago can be regarded as very modern in human history. ”
Taken together, the discovery provides important clues about how the three-day malaria parasite infects humans, helping scientists assess the likelihood of further spread of ape parasites into humans.
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