Gorilla, the possible of the origin of human Malaria parasite P. falciparum

 

When the emergence of disease outbreak, first thing that in scientists or epidemiologists mind are the resources or disease reservoirs are from our phylogenetic closely related species, chimpanzees. But recently the scientists found the different story on the origin of human Malaria P.falciparum, which is from gorilla.

A research team led by virologist Beatrice Hahn of the University of Alabama, Birmingham, used the polymerase chain reaction to amplify Plasmodium DNA from a whopping 2739 fecal samples from chimpanzees,gorillas, and bonobos.

Using single-template amplification strategies and a much larger collection of ape specimens than previously analysed, the scientists show here that wild-living chimpanzees and western gorillas are naturally infected with at least nine plasmodium species. Among more than 1,100 SGA derived mitochondrial, apicoplast and nuclear gene sequences from 80 chimpanzee and 55 gorilla samples, they found a total of nine sequences that were related to P. malariae, P. ovale or P. vivax. All others grouped within one of six chimpanzee or gorilla-specific lineages representing distinct Plasmodium species,three of which had not previously been described. Significantly, all currently available human P. falciparum sequences constitute a single lineage nested within the G1 clade of gorilla parasites. This indicates that human P. falciparum is of gorilla origin, and not of chimpanzee , bonobo or ancient human origin, and that all known human strainsmay have resulted froma single cross-species transmission event.

From the finding, what is still unclear is when gorilla P. falciparum entered the human population and whether present-day ape populations represent a source for recurring human infection.(when date of the jump from gorillas to humans). Plasmodium does not mutate much, she explained, making it difficult to calibrate a so-called molecular clock that enables evolutionary biologists to back-calculate the timing of a pathogen moving from one species to another.

According to Ajit Varki, an evolutionary biologist at UC San Diego,  he believes a human gene mutation, CMAH, which arose about 2 million years ago, may provide a clue to how and when the jump occurred. The mutation changes sialic acid receptors on red blood cells, rendering them much less susceptible to P. reichenowi, and Varki suspects that the gorilla P. falciparum similarly would have great difficulty infecting human cells.

This is also support by Michael Worobey, an evolutionary biologist who has also focused on the origin of the AIDS epidemic, is similarly intrigued that gorilla P. falciparum has not repeatedly infected humans. The finding can help clarify the evolutionary history of P. falciparum.

(for more information please read the article on Natures magazines 23rd september 2010, "Origin of the human malaria parasite Plasmodium falciparum in gorillas")