New Study Answers Key Public Health Question in Battle Against Malaria
Plasmodium falciparum research finds that malaria parasites are unlikely to jump to humans
In recent years, public health experts have increasingly explored the idea of eliminating the most dangerous malaria-causing parasite. But they have questioned whether getting rid of this species, called Plasmodium falciparum, would allow other species of the parasite to jump in and start infecting humans with malaria.
A new study led by a University of Maryland School of Medicine researcher indicates it is very unlikely that Plasmodium species that infect other animals—such as apes, birds and reptiles—would cross over easily to humans. Using sophisticated genetic analysis, researchers found evidence showing that five other common Plasmodium species have not changed which animals they infect for at least 3 million years.
Malaria is a leading cause of disease and death throughout the world; every year it infects over 200 million people, and causes more than half a million deaths. In parts of sub-Saharan Africa and South Asia, the disease is common and causes enormous suffering and hardship.
The new study was published online last month in the journal Molecular Biology and Evolution. The research team included scientists and statisticians from the National Center for Biotechnology Information at the National Institutes of Health and the Applied Mathematics & Statistics, and Scientific Computation program at the University of Maryland, College Park (UMCP).
“This is a key question – how likely are these parasite species to jump to humans?” says the study’s lead author Joana C. Silva, an assistant professor in the Department of Microbiology and Immunology and at the Institute for Genome Sciences at the UM SOM. “And according to our results, 'host switching' by malaria-causing parasites is not at all a common event, on an evolutionary time scale.”
More than 200 Plasmodium species have been identified. Plasmodium falciparum is the most lethal of the five that are known to infect humans. Researchers are examining new approaches to reduce or eliminate Plasmodium falciparum by developing vaccines against it, for example, or spreading a bacterium that kills the mosquitoes that carry it. But some scientists have expressed concern that Plasmodium falciparum’s ecological niche might be quickly filled by other Plasmodium species.
The research team looked at hundreds of genes spread across five different species of Plasmodium. Their goal was to discover how closely related the genes were—in effect, how long ago they had diverged from each other. If they had separated recently, it was more likely that they could jump from infecting one species to another.
To get their results, the researchers developed a new statistical approach to determine when Plasmodium species split off from one another. The new method uses molecular data from thousands of genes; current techniques, by contrast, use at most sequences from dozens. This new approach is not only more reliable, but also faster.
David Harris—a Ph.D. student in the UMCP Applied Mathematics & Statistics, and Scientific Computation program—developed the statistical methods used in this research.
“This is an exciting integration of mathematics and genetics,” says Harris. “It’s great to be able to use mathematics in a way that has the potential to inform practical policy decisions.”
The research was supported by the National Institute of Allergy and Infectious Diseases (NIAID) at the National Institutes of Health, and by the Intramural Research Program of the National Library of Medicine.
The research paper, “A new method for estimating species age supports the co-existence of malaria parasites and their mammalian hosts,” Joana C. Silva, Amy Egan, Cesar Arze, John L. Spouge and David G. Harris, was published online Jan. 13, 2015 in the journal Molecular Biology and Evolution.
Media Relations Contact: (UM SOM) 410-706-5260; (UMCP) Abby Robinson, 301-405-5845, email@example.com
Writer: David Kohn/UM SOM
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