Via Xinhua, a fascinating report: U.S. researchers trace malaria in humans to one infected gorilla. Excerpt:
To investigate the connections between parasite species, Beatrice Hahn of the University of Alabama, Birmingham and colleagues isolated malaria parasites from primate feces specimens the researchers had collected for their work on the origins of HIV. More than 1,000 chimpanzee samples, 805 gorilla samples and 107 bonobo samples were tested, making this the largest study of its kind.
Based on the testing, the researchers estimate that between 32 percent and 48 percent of wild chimpanzees and western gorillas are infected with malaria parasites. Samples from eastern gorillas and bonobos did not show any infection.
A genetic analysis showed that none of the chimpanzee malaria parasites were closely related to human P. falciparum. However, one subtype of gorilla parasite was nearly identical to the human strain. The genetic lineage of the parasite suggests that it evolved after making a single jump from gorilla to human.
"When you take all the sequences that have been published for all human Plasmodium falciparum worldwide, and when you put it in this family tree analysis, you see that they all have one single common ancestor," Hahn said in remarks published by LiveScience on Wednesday. "That tells you that this was the result of a single cross-species transmission event."
Researchers can't say exactly when the parasite first infected humans, because little is known about the rate of evolution for P. falciparum. However, the leap probably occurred between 5,000 and 300,000 years ago, Hahn said.
An estimated 250 million people become infected with malaria each year and nearly a million die from it, according to the World Health Organization.
Nature News has a story about this, with a link to the original report.
