Tuesday, March 16, 2010

Duffy negative

"In a paradigm changing discovery," malaria illness "has been identified in a population historically thought to be resistant to the disease." The Duffy blood group protein, located on the surface of red blood cells, acts as a receptor for the malaria parasite and facilitates malaria illness in humans. Duffy-negative population groups (people who do not have the Duffy antigen) were considered resistant to malaria because their blood cells lacked the receptor through which malaria invades.

However, "according to researchers from Case Western Reserve University School of Medicine, Pasteur Institute, and the Madagascar Ministry of Health", Duffy-negative individuals may experience illness from malaria. "In a study of more than 600 individuals from eight communities covering the main malaria transmission areas of Madagascar, the researchers found that 10 percent of people experiencing clinical malaria were Duffy-negative and infected with P. vivax."

"Since the early 1920s, it has been widely accepted that people of African ancestry are resistant to P. vivax blood-stage infection and clinical malaria. The Duffy-negative blood group, one of the more than 30 blood types, is predominant in most African ethnic groups" (Case). "Duffy-negative people usually have relatively recent ancestors from historically malaria prone regions. The highest concentration of Duffy-negative people in the world is in West Africa, where more than 95% of people are missing the protein on their red blood cells. Reflecting their African ancestry, 68% of African-Americans are also Duffy-negative" (23andme).

Malaria parasites are changing. Mutations allow the parasite population to become resistant to commonly-used drugs, develop in areas of high altitude, and now may enable them to cause illness in Duffy-negative people.

People with "this blood type, can have P. vivax living dormant in their liver cells where it does not make people sick." What "distinguished Duffy-negatives from all others was that the malaria parasite was unable to cross the threshold from liver cells to blood cells." However, during this study the team documented "photographic evidence of the parasite's presence within red blood cells of many Duffy-negative people experiencing malarial illness."

"The study confirms that P. vivax is not dependent on the Duffy antigen for establishing blood-stage infection and disease in Madagascar. Evolution of new parasite strains, infiltrating a new group of people who are Duffy-negative, seems to be occurring within a population of people from different ethnic backgrounds," says Peter A. Zimmerman, Ph.D., the study's senior author and Professor of International Health, Genetics and Biology in the Center for Global Health and Diseases at Case Western Reserve University School of Medicine. "These findings will have a major impact on efforts to eliminate malaria worldwide, particularly in large regions of Duffy-negative west, central and southern Africa."

"In Madagascar, malaria is endemic to more than three-quarters of the island. With almost one million clinical cases reported each year, this disease is a major public health problem" (Case).


23andMe. "Malaria resistance." https://www.23andme.com/health/Malaria-Resistance-Duffy-Antigen/howitworks/ [Image]

Case Western Reserve University. "Duffy-Negative Blood Types No Longer Protected from P. Vivax Malaria." ScienceDaily 15 March 2010. 16 March 2010 .

Horuk et al. (1993) . “A receptor for the malarial parasite Plasmodium vivax: the erythrocyte chemokine receptor.” Science 261(5125):1182-4.

Kasehagen et al. (2007) . “Reduced Plasmodium vivax erythrocyte infection in PNG Duffy-negative heterozygotes.” PLoS ONE 2(3):e336.

Michon et al. (2001) . “Duffy-null promoter heterozygosity reduces DARC expression and abrogates adhesion of the P. vivax ligand required for blood-stage infection.” FEBS Lett 495(1-2):111-4.

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