Deadly Malaria Came To Humans From Gorillas, Not Chimps
US-led study of malaria parasites in wild apes in Africa showed that the parasite that causes the most deadly form of the disease in humans, Plasmodium tropical, not from chimpanzees, as first thought, but from the gorillas.
You can read how lead researcher Dr. Beatrice Hahn of the University of Alabama at Birmingham in the U.S., and colleagues from the United States, the Republic of the Congo, Republic of Cameroon, France and Britain, came to this conclusion in a paper published online in the journal Nature on September 23.
Of the five species of human malaria parasites by causing mosquitoes, P. Falciparum is the most common and most deadly, it causes hundreds of millions of malaria cases and over one million deaths a year. However, its evolutionary roots are much discussed topic.
Prior to this study it was thought that AP was the closest relative of the tropical P. reichenowi, which infects chimpanzees, but it is based on small studies that included only a few monkeys, and even fewer in the wild.
For their study, Han and his colleagues analyzed DNA samples of thousands of litters of African wild life, monkeys and found that the Plasmodium parasite is most closely related to the human one, can be found in western gorillas rather than chimpanzees or bonobos.
Their results also show that all existing strains of the human form evolved from a single transition from one species to another.
Dr. Daniel Jeffares, an evolutionary biologist at University College London, UK, who was not one of the authors of this document, told Nature News that it will take more samples than the number used in this study to confirm that this is a one-time events which are transmitted from infected gorillas to humans.
Nevertheless, he described the results of the study as "eyes", and that this document is a "game changer" in terms of what we know about the parasites.
Evolutionary biologist Paul Sharp, University of Edinburgh, United Kingdom, one of the authors, said that they are "interested in whether the interspecies jump like this could happen in the future."
This can be a very topical issue in the campaign against malaria today, as this study also suggests there are potential reservoirs Plasmodium monkeys living in the wild today.
In their study, Khan, Sharp and colleagues have identified and characterized Plasmodium species in nearly 3000 fecal samples from wild monkeys living in Central Africa. For their analysis they developed a "one-genome amplification strategy that allowed them to search for specific DNA sequences of the parasite Plasmodium.
They found evidence of Plasmodium infection in chimpanzees (Pan troglodytes) and western gorillas (Gorilla gorilla), but not in Eastern gorilla (Gorilla beringei) or bonobos (Pan paniscus).
"Monkey plasmodial infections were widespread, common and almost always of mixed species of parasites," they wrote.
The researchers analyzed more than 1100 mitochondria, apicoplast (the type of cellular organelle found in some species of Plasmodium) and nuclear DNA sequences of chimps and gorillas, and found that 99 percent of them were "grouped into one of the six host-specific lines from different Plasmodium species within the subgenus" Laverania.
One species of Plasmodium, of the western gorillas were almost identical to P. falciparum.
When they compared the sequences of the full-length human mitchondrial P. falciparum with views of the gorilla samples, they found that they formed "monophyletic line" indicating their same recent ancestor (in other words, they are adjacent branches on the same branch of the evolutionary tree).
Khan and colleagues concluded that:
"These results indicate that SP has a tropical origin of the gorillas, but not chimpanzees, bonobos, or ancient human origins."
"The origin of the human malaria parasite Plasmodium Tropical gorillas." Liu Weimin, Yingying Li, Gerald H. Read, Rebecca S. Rudicell, Joel D. Robertson, Brandon F. Keele, Jean-Bosco N. Ndjango, Crickette M. Sanz, David B. Morgan, Sabrina Locatelli, Mary K. Gonder Philip J. Kranzusch, Peter D. Walsh, Eric Delaporte, Eitel Mpoudi-Ngole, A. Georgiev, N., Martin Muller, George M. Shaw, Martin Peters, Paul M. Sharp, Julian C. Rayner and Beatrice H. Hahn. Nature, Volume 467, pages 420-425, published on 23 September 2010. DOI: 10.1038/nature09442