Amazing Science

Several million years ago, Plasmodium falciparum – the parasite that causes most cases of human malaria – jumped into humans from other apes. We’ve known as much for decades but for all this time, we’ve pinned the blame on the wrong species. A new study reveals that malaria is not, as previously thought, a disease that came from chimpanzees; instead it’s an unwanted gift from gorillas.

Until now, the idea of chimps as the source of human malaria seemed like a done deal. Just last year, I covered a study which said that a related chimp parasite called Plasmodium reichenowi is the ancestor of P.falciparum.According to Stephen Rich from the University of Massachussetts,P.reichenowi crossed the species barrier from chimps to humans just once in history – a defining moment that gave rise to P.falciparum.

But to Weimin Liu from the University of Alabama, something wasn’t quite right. People seemed to have settled on a chimpanzee conclusion without thoroughly testing for Plasmodium in other apes. Fortunately, Liu’s team was well placed to fill in those blanks. For their research, they had already amassed a massive collection of ape faeces: an unenviable collection of 1,827 samples from chimps, 805 from gorillas and 107 from bonobos. Virtually all of these samples came from wild apes with little human contact; only 28 came from a habituated group of gorillas.

Liu scoured all of these samples for Plasmodium DNA, sequenced what he could find, and built a family tree that charted the evolutionary relationships between them. His results were very clear. For a start, Plasmodium parasites don’t infect either eastern gorillas or bonobos, but they do infect chimpanzees and western gorillas. That narrows down the source of human malaria to these two apes.

Liu also found that all of the samples of P. falciparum taken from humans were most closely related to a single lineage of gorilla parasites. P.reichenowiis an exclusively chimp parasite, belonging to a different branch of thePlasmodium family tree. The answer was clear: P.falciparum did not evolve from P.reichenowi and it didn’t come from chimpanzees. Instead, it jumped into humans from western gorillas.

Imagine an insect repellant that not only is thousands of times more effective than DEET – the active ingredient in most commercial mosquito repellants – but also works against all types of insects, including flies, moths and ants. That possibility has been created by the discovery of a new class of insect repellant made in the laboratory of Vanderbilt Professor of Biological Sciences and Pharmacology Laurence Zwiebel and published iit in Proceedings of the National Academy of Sciences.

In preliminary tests with mosquitoes, the researchers found the new class of repellant,  called Vanderbilt University Allosteric Agonist or VUAA1, to be thousands of times more effective than DEET. The compound works by affecting insects’ sense of smell through a newly discovered molecular channel.

“If a compound like VUAA1 can activate every mosquito odorant receptor at once, then it could overwhelm the insect’s sense of smell, creating a repellant effect akin to stepping onto an elevator with someone wearing too much perfume, except this would be far worse for the mosquito,” said Patrick Jones, a post-doctoral fellow who conducted the study with graduate students David Rinker and Gregory Pask.