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Contrasting Epidemiology and Genetic Variation of Plasmodium vivax Infecting Duffy Negatives across Africa.

OBJECTIVES
Plasmodium vivax malaria was thought to be rare in Africans who lack the Duffy blood group antigen expression. However, recent studies indicate that P. vivax can infect Duffy-negative individuals and has penetrated into areas of high Duffy-negativity across Africa. This study compares epidemiological and genetic features of P. vivax between African regions.


METHODS
We utilized a standardized approach to identify and quantify P. vivax from Botswana, Ethiopia, and Sudan, where Duffy-positive and Duffy-negative individuals coexist. We sequenced Duffy Binding Protein (DBP) gene and inferred genetic relationships among all Africa P. vivax.


RESULTS
Among 1,215 febrile patients, the proportions of Duffy negativity range from 20-36% in East Africa to 84% in Southern Africa. P. vivax prevalence among Duffy-negative populations ranging from averaged 9.2% in Sudan to 86% in Botswana. Parasite density in Duffy-negative is significantly lower than in Duffy-positive infections. P. vivax in Duffy-negative populations were not monophyletic. Duffy-negative and Duffy-positive P. vivax shared similar DBP haplotypes and occurred in multiple well-supported clades.


CONCLUSIONS
Duffy-negative Africans are not resistant to P. vivax and the public health significance should not be neglected. This study highlights need for standardized approach and more resources/training to diagnosis of vivax malaria in Africa.