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

Abstract

Background Malaria in sub-Saharan Africa (sSA) is thought to be hugely caused by Plasmodium falciparum . Recently, growing reports of cases due to P. ovale , P. malariae , and P. vivax have been significantly reported to play a role in malaria epidemiology in sSA. This in fact is due to the usage of very sensitive diagnostic tools (e.g. PCR) which have highlighted the underestimation of non-falciparum malaria in this sub-region. P. vivax was historically thought to be absent in sSA due to the high prevalence of the Duffy null antigen in individuals residing in this sub-continent. For example, recent studies reporting the detection of vivax malaria in Duffy-negative individuals from Mali, Mauritania, Cameroon to mention a few challenges this notion.Methods Following our earlier report of P. vivax in Duffy-negative individuals, we have collected and assessed RDT and/or microscope malaria positive samples following the conventional PCR method and DNA sequencing to confirm both single/mixed infections as well as the Duffy status of the individuals.Results Amplification of Plasmodium gDNA was possible in 59.9% (145/242) of the evaluated isolates and as expected P. falciparum was the most predominant (91.7%) species identified. Interestingly, four P. vivax isolates were identified either as single (3) or mixed (1 – P. falciparum / P. vivax ) infection. Sequencing results confirmed, all vivax isolates as truly vivax malaria and their Duffy status to be that of the Duffy-negative genotype.Conclusion Identification of more vivax isolates among these Duffy-negative individuals from Nigeria, substantiate the expanding body of evidence on the ability of P. vivax to infect RBCs that do not express the DARC gene. Hence, such genetic-epidemiological study should be conducted at the national level in order to evaluate the actual burden of P. vivax in the country.