Illustration of malaria merozoite entering a red blood cell. The malaria parasite spends this part of its life-cycle in red blood cells, the parasite digests haemoglobin to obtain amino acids for protein synthesis. The World Health Organization has estimated that in 2010, there were 219 million documented cases of malaria with as many as 1.2 million deaths. To date no effective vaccine exists for malaria.

Source: BBC

Malaria is one of several deadly diseases that has jumped the species barriers from animals into humans.

It kills almost half a million people per year, and can be transmitted into humans by a single mosquito bite.

The most deadly form of malaria is caused by the Plasmodium falciparum protozoan parasite, one of several malaria-causing parasites.

But mosquitoes are simply the carriers, not the source. This has made tracing the parasite’s origin challenging.

In order to understand how a disease evolves, it is crucial to know where and when it began affecting humans. This can help scientists unpick the miniscule genetic changes that could have made it so deadly.

African apes harbour at least six Plasmodium species (Credit: Anup Shah/Naturepl.com)

In 2010 scientists made a breakthrough. By analysing western gorilla faecal samples that contained Plasmodiumparasites, they found the human version – P. falciparum – was closely related to one of the three Plasmodium parasites that gorillas host.

It was not clear when the gorilla parasite jumped into humans

It revealed, for the first time, that the deadliest form of human malaria came from gorillas, not chimps or other species of early-humans as others had previously proposed.

This is how it started: a mosquito bit an infected gorilla and then transmitted the parasite to a human with another bite. Once it was in humans it could then spread rapidly, as long as there were enough mosquitoes to pass the parasite from person to person.

But the story was still incomplete. In particular, it was not clear when the gorilla parasite jumped into humans.

The problem was that the faecal samples contained only snippets of the gorilla Plasmodium DNA. To get full genome sequences that would help pin down the time of transmission, the researchers needed blood.

Read more