Washington, Jan 20 (IANS) A malignant malaria parasite that infects humans comes from another closely related bug, found in equatorial African chimpanzees and gorillas, which could complicate its eradication, says a new study.
P. falciparum accounts for 85 percent of malignant malaria infections in humans and nearly all deaths from the disease, said University of California-Irvine (UC-I) biologist Francisco Ayala and colleagues.

“Hundreds of billions of dollars are spent each year toward ridding humans of malignant malaria. But success may be pyrrhic… because we could be re-infected by gorillas just as we were originally infected by chimpanzees a few thousand years ago,” said Ayala.

In August, Ayala and colleagues published a study reporting that P. falciparum had been transmitted to humans from chimpanzees perhaps as recently as 5,000 years ago - and possibly through a single mosquito. Before then, malaria’s origin had been unclear.

The researchers analysed faecal samples from 125 wild chimpanzees and 84 gorillas in Cameroon and tested blood samples of three gorillas in Gabon.

They identified two new closely related species of malaria parasites - Plasmodium GorA and Plasmodium GorB - that infect gorillas. The animals also were found to harbour P. falciparum, previously thought to only infect humans.

Researchers cautioned that increased contact between primates and humans, mostly because of logging and deforestation, creates a greater risk of new parasites being transmitted to humans.

Chimpanzees were known to carry the parasite Plasmodium reichenowi, but most scientists assumed the two parasites had existed separately in humans and chimpanzees for the last 5 million years.

The discovery could aid the development of a vaccine for malaria, which each year causes two million infant deaths and sickens about 500 million people, mostly in sub-Saharan Africa, said an UC-I release.

It also furthers understanding of how infectious diseases such as HIV, SARS, and avian and swine flu can be transmitted to humans from animals.

These findings were published in the Proceedings of the National Academy of Sciences.