The hide and seek of Plasmodium vivax in West Africa: report from a large-scale study in Beninese asymptomatic subjects.

Philippe Poirier,André Bigot,Elodie Haar,Lydia Arnoux,Casimir D Akpovi,Nicodeme W Chabi,Marie-Louise Coquelin De L’Isle,Denis Filisetti,Sylvie Perrotey,Jean-Philippe Lemoine,Ambaliou Sanni,Pascal S Atchade,Ahmed Abou-Bacar,Alexander W Pfaff,Julie Brunet,Cécile Doderer-Lang,Ludovic Anani,Ermanno Candolfi

doi:10.1186/s12936-016-1620-z

Abstract

Background Plasmodium vivax is considered to be absent from western Africa, where the prevalence of Duffy-negative red blood cell phenotype proves to be high. Several studies have, however, detected P. vivax infection cases in this part of Africa, raising the question of what is the actual prevalence of P. vivax in local populations. MethodsThe presence of P. vivax was investigated in a large population of healthy blood donors in Benin using microscopy, serology and molecular detection. The seroprevalence was measured with species-specific ELISA using two recombinant P. vivax proteins, namely rPvMSP1 and rPvCSP1. Specific molecular diagnosis of P. vivax infection was carried out using nested-PCR. The performances and cut-off values of both rPvCSP1 and rPvMSP1 ELISA were first assessed using sera from P. vivax-infected patients and from non-exposed subjects.ResultsAmong 1234 Beninese blood donors, no parasites were detected when using microscopy, whereas 28.7% (354/1234) of patients exhibited had antibodies against rPvMSP1, 21.6% (266/1234) against rPvCSP1, and 15.2% (187/1234) against both. Eighty-four samples were selected for nested-PCR analyses, of which 13 were positive for P. vivax nested-PCR and all Duffy negative. ConclusionThe results of the present study highlight an unexpectedly high exposure of Beninese subjects to P. vivax, resulting in sub-microscopic infections. This suggests a probably underestimated and insidious parasite presence in western Africa. While the vaccination campaigns and therapeutic efforts are all focused on Plasmodium falciparum, it is also essential to consider the epidemiological impact of P. vivax.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-016-1620-z) contains supplementary material, which is available to authorized users.

Highlights

Plasmodium vivax is considered to be absent from western Africa, where the prevalence of Duffy-nega‐ tive red blood cell phenotype proves to be high
Assessment of rPvMSP1 and rPvCSP1 ELISA The assay sensitivity was first evaluated on 41 sera from P. vivax-positive febrile patients diagnosed using microscopy and confirmed by species-specific PCR
Specificity was subsequently evaluated on 280 sera from non-exposed-to-malaria French blood donors

Summary

Introduction

Plasmodium vivax is considered to be absent from western Africa, where the prevalence of Duffy-nega‐ tive red blood cell phenotype proves to be high. While the overall P. vivax prevalence in Africa remains low, the parasite is considered to be present in the Horn of Africa, yet almost absent in West Africa To date, this has been mainly accounted for by the absence of the red blood cell surface Duffy antigen among Africans living in this area [4]. P. vivax infections were documented in Duffy-negative subjects in Brazil [5, 6], Ethiopia [7, 8], Madagascar [9], and in West African countries, such as Mauritania [10], Cameroon [11, 12], Equatorial Guinea, and Angola [13] According to these different studies, the prevalence of P. vivax in West-Africa is probably underestimated and large-scale epidemiological studies are required to investigate the burden of P. vivax infections [3]. For epidemiological studies to assess P. vivax infections, molecular biology has been commonly used and shown to be more sensitive than microscopy [3, 15]

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