Evolution of Plasmodium falciparum, Cause of Malignant Malaria
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Posted by Rosemary Drisdelle Aug 12, 2009 |
A recent scientific paper titled “The Origin of Malignant Malaria” (see full reference below) sheds light on how one of the worst parasites to infect humans evolved. Reports in the media paraphrase the paper as saying that Plasmodium falciparum transferred from chimpanzees to humans between 5000 and 10,000 years ago, and speculate on why the parasite causes such serious disease. The authors of the paper, however, make no conclusions about either of these things.
Stephen M, Rich and others conclude that the parasite P. falciparum evolved from the closely related chimpanzee parasite P. reichenowi relatively recently, and that the transfer happened only once. Both conclusions are supported by the fact that P. reichenowi has considerable genetic diversity while P. falciparum has very little (indicating that the chimpanzee species has been evolving much longer).
On the subject of when the transfer occurred, the authors comment that “considerable time, …many tens or hundreds of thousands of years, may have elapsed” (p. 4 of 6). They discuss the previous work of others, which indicates P. falciparum expanded and began causing serious widespread disease after the introduction of agriculture—perhaps between 5000 and 10,000 years ago. Its increased success was probably due to a combination of factors including deforestation, climate change, and the development of malaria-carrying mosquitoes that preferred human blood. It’s not clear whether P. falciparum caused serious disease before the expansion, or whether it underwent a genetic change that favored success and spread as well.
Read the paper by Rich, Leendertz, Xu, and others:
“The Origin of Malignant Malaria.” Rich, Stephen. M., Fabian H. Leendertz, Guang Xu et al. Proceedings of the National Academy of Sciences of the United States of America (PNAS early edition).
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The Origin of Plasmodium falciparum. Where Did Malignant Malaria Come From?
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