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[KAMPALA] New studies have found that one of the world’s most common malaria parasites — called Plasmodium vivax — that causes vivax malaria, is rapidly evolving and could overcome the natural resistance conferred by a blood type found in millions of people.
Researchers say this evolution could make malaria control and elimination more complicated, affect the treatment cost, increase drug resistance and make it harder to develop a malaria vaccine.
The research was released last month (19 November) at the American Society of Tropical Medicine and Hygiene annual meeting in Washington DC, United States.
“Health care providers need to be on the lookout for P. vivax, specifically, across Africa. At present, methods to diagnose it are neither specific nor sensitive enough.”
Peter Zimmerman, Case Western Reserve University
“Health care providers need to be on the lookout for P. vivax, specifically, across Africa. At present, methods to diagnose it are neither specific nor sensitive enough,” says Peter Zimmerman of the US-based Case Western Reserve University and a co-author of the two new studies that have been published in PLOS Neglected Tropical Diseases (21 November and 5 December).
Historically, P. vivax has been suggested to be nonthreatening and not cause the severe morbidity or mortality of Plasmodium falciparum, a common malaria parasite, but this notion is not correct,” says Zimmerman
In a multi-country study published on 21 November, the researchers used new genome sequence data from parasites collected from one patient in Madagascar in 2010 and isolates of the parasite in people with symptoms of vivax malaria returning to France from countries such as Cambodia, Madagascar and Sudan between 1997 and 2009.
They found several possible new biological mechanisms that could be giving P. vivax new ways to infect people who were previously considered to be naturally protected. These people lacked a protein called the Duffy binding protein, which hinders the vivax malaria parasites to enter red blood cells.
Madagascar was of particular interest because of the occurrence of high rates of Duffy-negative individuals, causing a surge of Duffy-negative infections among the populations, according to Zimmerman.
The other study, published on 5 December, focused on generating new genes of P. vivax from a Cambodian patient and comparing the outcome to a reference genome.
“Our analyses reveal many P. vivax DNA sequences that are absent from the reference genome and contain 792 predicted genes,” the researchers wrote in the journal.
In Cambodia they discovered a new way for P. vivax to invade red blood cells and a previously unknown gene that “harbours all the key features” of being able to invade red blood cells in a way that is similar to the deadlier malaria parasite — P. falciparum.
Zimmerman says it is necessary to perform more basic research to understand how the parasite infects red blood cells to better prepare a specific vaccine and to develop new drugs to kill the parasite at all stages of its life cycle in human infection.
Ibrahim Kasirye, principal researcher fellow with the Makerere University, Uganda, says that given 95 per cent of Africans were previously protected from this strain, the evolution of the parasite suggests a potential increase in the malaria burden across Africa.
He says very little research has been dedicated to the parasite but it should be treated with priority like the other malaria parasites.
Link to multi-country study in PLOS Neglected Tropical Diseases
Link to Cambodia study in PLOS Neglected Tropical Diseases
This article has been produced by SciDev.Net's Sub-Saharan Africa desk.
1. PLOS Neglected Tropical Diseases doi: 10.1371/journal.pntd.0002489 (2013)
2. PLOS Neglected Tropical Diseases doi: 10.1371/journal.pntd.0002569 (2013)