Distribution of Duffy Phenotypes among Plasmodium vivax Infections in Sudan

Negative Duffy expression on the surface of human red blood cells was believed to be a barrier for Plasmodium vivax infection in most Africans. However, P. vivax has been demonstrated to infect Duffy-negative individuals in several Central and East African countries. In this study, we investigated the distribution of Duffy blood group phenotypes with regard to P. vivax infection and parasitemia in Sudan. Out of 992 microscopic-positive malaria samples, 190 were identified as P. vivax positive infections. Among them, 186 were P. vivax mono-infections and 4 were mixed P. vivax and Plasmodium falciparum infections. A subset of 77 samples was estimated with parasitemia by quantitative real-time PCR. Duffy codons were sequenced from the 190 P. vivax positive samples. We found that the Duffy Fy(a-b+) phenotype was the most prevalent, accounting for 67.9% of all P. vivax infections, while homozygous Duffy-negative Fy(a-b-) accounted for 17.9% of the P. vivax infections. The prevalence of infection in Fy(a-b+) and Fy(a+b-)were significantly higher than Fy(a-b-) phenotypes (p = 0.01 and p < 0.01, respectively). A significantly low proportion of P. vivax infection was observed in Duffy negative individuals Fy(a-b-). This study highlights the prevalence of P. vivax in Duffy-negatives in Sudan and indicates low parasitemia among the Duffy-negative individuals.