Presence of additional P. vivax malaria in Duffy negative individuals from Southwestern Nigeria

Abstract Malaria in sub-Saharan Africa (sSA) is thought to be hugely caused by Plasmodium falciparum and very infrequently by P. ovale, P. malariae, with P. vivax not even being considered to be of any significant role. However, with the availability of very sensitive diagnostic tool, it has become more clear that, the percentage of non-falciparum malaria in this sub-region has been underestimated. P. vivax was historically thought to be absent in sSA due to the high prevalence of the Duffy null antigen in individuals residing here. Nevertheless, recent studies reporting the detection of vivax malaria in Duffy-negative individuals challenges this notion. Following our earlier report of P. vivax in Duffy-negative individuals, we have re-assessed all previous samples following the classical PCR method and sequencing to confirm both single/mixed infections as well as the Duffy status of the individuals. Interestingly, fifteen additional Plasmodium infections were detected, representing 5.9% in prevalence from our earlier work. In addition, P. vivax represents 26.7% (4/15) of the new isolates collected in Nigeria. Sequencing results confirmed, all vivax isolates as truly vivax malaria and their Duffy status to be that of the Duffy-negative genotype. The identification of more vivax isolates among these Duffy-negative individuals from Nigeria, substantiate the expanding body of evidence of the ability of P. vivax to infect RBCs that do not express the DARC gene. Hence, such geno-epidemiological study should be conducted at the national level in order to evaluate the actual burden of P. vivax in the country.