How parasite successfully evades malaria elimination efforts worldwide

Washington : Scientists have discovered that Plasmodium vivax – the parasite that causes the most common form of malaria – share the same genetic variations, even when the organisms are separated across continents.

The discovery raises concerns that mutations to resist existing medications could spread worldwide, making global eradication efforts even more difficult.

The researchers, including Cleveland-based David Serre and Peter Zimmerman, Didier Menard (Institut Pasteur-Cambodia) and Arsene Ratsimbasoa (Madagascar National Malaria Control Program) are the first to sequence the genome of the parasite Plasmodium vivax, taken from patients at coverage needed to verify genome-wide DNA sequence variation.

The genome contains all of the organism”s inheritable information.

The ability to sequence is crucial to understanding the hard-to-study parasite, which annually causes up to 250 million cases of malaria and places an economic burden, mostly on the poor.

The scientists at first were surprised to find little genetic variation specific to different locations among the samples, which came from humans in Madagascar and Cambodia and South America.

“The parasite’s life cycle enables P. vivax to be a microbial globe-trotter,” said Peter Zimmerman, professor of international health, genetics and biology in the Center for Global Health and Diseases at Case Western Reserve University School of Medicine.

In parts of the world where Plasmodium vivax malaria is endemic, the primary infection gets into the red blood cells and makes people sick, he explained. When they feel better, people resume their normal activities and travel.

But a portion of the infectious form can remain in their liver, where it may lay dormant for months or a year, then re-emerges into the blood when that person is in a different place.

“In that new place, local mosquitoes bite, become infected, and start spreading the P. vivax parasite and its genome in locations that can be a long distance away from where the original human infection occurred,” Zimmerman, a senior author of the new study, said.

This ability for worldwide travel raises concerns among the researchers.

Serre said “Our work provides the first report on genome-wide variation of this malaria parasite and provides the malaria research community with more than 80,000 genetic markers that can now be used for trait mapping or population monitoring.”

“This is a critical step to understand the biology of this parasite that cannot be studied in the laboratory yet affects millions of people each year.”

“These studies will help advance the understanding of P. vivax biology and how the parasite successfully evades malaria elimination efforts worldwide,” he added.

The researchers report their findings in the online journal PLoS Neglected Tropical Diseases.