New Research Shows Deadliest Form of Malaria is Younger Than Previously Believed and Comes From a Single Parasite Ancestor
For immediate release: July 19, 2001
Boston, MA— Researchers from the Harvard-Oxford Malaria Genome Diversity Project studying the genome sequence of the most lethal strain of malaria, Plasmodium falciparum, have linked the origin of the parasite to a single progenitor of more recent origin than previously thought. The findings could help explain how malaria spread throughout the human population over the past several thousand years and pinpoint the source of the variety of genetic mutations that makes P.falciparum resistant to anti-malarial drugs. The findings appear in the July 20 issue of the journal Science.
Malaria is the world’s most serious parasitic tropical disease and kills more people than any other communicable disease except for tuberculosis. P.falciparum, the most lethal form of the disease accounts for the majority of infections, 200 to 300 million, resulting in 1 to 3 million deaths annually. Malaria is a curable disease if promptly diagnosed and adequately treated. Increased risk of the disease is associated with land use changes such as agricultural and irrigation projects in frontier areas like the Amazon, South East Asia and Sub-Saharan Africa and by the emergence and spread of drug resistant parasites.
The researchers examined and sequenced introns from the first completely sequenced parasite chromosomes covering wide-ranging geographic areas including Africa, Honduras, Thailand and Papua New Guinea. They were able to estimate that the most recent common ancestor of all P.falciparum in existence dates back between 3,000 and 10,000 years, a far more recent estimate than the previously believed ancient origins.
The estimate is supported by evidence from natural history dating back less than 6,000 years ago with the advent of slash and burn agricultural methods in African rainforests and recently discovered gene mutations in humans. The newly cleared sun-filled terrain, with pools and puddles of water, could have provided the ideal mosquito vector for P.falciparum.
With a sufficient human and vector populations large enough to maintain transmission of the parasite, the researchers suggest that two evolutionary courses for the single ancestor are possible. The sole ancestor of all existing P.falciparum established itself either from a single strain supplanting the others through superior strength or, less likely, by the chance coincidence to spread.
Dyann Wirth is Director of the Harvard Malaria Initiative and Professor of Immunology and Infectious Diseases in the Department of Immunology and Infectious Diseases at the Harvard School of Public Health, she said, “Our research suggests a new mechanism developed by the parasite to rapidly generate diversity in selected genes and has important implications for drug and vaccine development.”
The researcher was conducted by teams at the University of Oxford led by Professor Karen Day and at Harvard University led by Professors Daniel Hartl and Dyann Wirth. The research was funded by the National Institutes of Health, the Wellcome Trust and the Burroughs-Wellcome Fund.
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