Molecular evidence of Plasmodium vivax infection in Duffy negative symptomatic individuals from Dschang, West Cameroon

Abstract

Background: Plasmodium vivax infection is known to be rare in West/Central Africa, the most accepted explanation being the lack of expression of erythroid Duffy antigen in the local human populations. Duffy negativity prevents the parasite to exploit the entry mechanism on the red blood cell surface. However, there are a growing number of reported vivax infections in Duffy-negative individuals. Data on P. vivax circulation in Cameroon are limited. The aim of the study was to evaluate the P. vivax presence, and its association with the Duffy genotype in West Cameroon.

Results: Overall, 484 blood samples were collected consecutively from febrile outpatients attending the Dschang's Hospital (West Cameroon) during a 3-months period. Plasmodium vivax infection was detected by PCR in 5.6% (n = 27/484) of the cases, representing 38.6% (n = 27/70) of all Plasmodium infections detected. All P. vivax infected individuals showed a Duffy-negative genotype, and the frequency of Duffy-positive individuals in the whole tested population was 1.7%.

Conclusions: The results of this study confirm the circulation of P. vivax in Cameroon, as well as that the lack of expression of Duffy-antigen does not confer full protection against vivax malaria acquisition.

Keywords: Cameroon; Duffy antigen genotype; Malaria; Plasmodium vivax.

Fig. 1

Plasmodium vivax (a) and Plasmodium spp. (b) sequence alignment* DNA sequence alignment of the four reference species (P. vivax, an. U03079; P. malariae, an. M54897; P. ovale an. L48987; P. falciparum, an. JQ627152) with four P. vivax positive amplicons (n. 424, 455, 452, 457) sequenced (A) and three Plasmodium spp. positive samples (n. 455, 365, 483) sequenced according to Rougemont et al. [26] (B). *Identical nucleotides are shown as dots, mismatches and gaps are highlighted in gray

Fig. 2

Duffy antigen genotyping (SNP -33T>C in GATA box, DARC gene) by melting curve analysis. a Chromatogram of the Caucasian Duffy-positive phenotype (-33TT genotype), reference sample. b Chromatogram of the Cameroonian Duffy-negative phenotype (-33CC genotype), reference sample. c Melting curve analysis of the two reference samples: melting temperatures of 60.5 and 64.5 °C for Duffy-positive (Caucasian) and Duffy-negative (Cameroonian), respectively. d Melting curve analysis of a representative group of samples, including the two reference samples. Two heterozygous samples (thick red and blue lines) are also shown. Negative controls are in the lower part of the melting curves of c, d

Fig. 3

Plasmodium vivax infection in Cameroon. Cameroonian regions: FN Far North, N North, A Adamaoua, NW North-West, SW South-West, W West, L Littoral, C Centre, S South, E East. Study sites: 1 Bolifamba village (South-West Region): 13/269 (4.8%) P. vivax infections [18]; 2 Douala (Littoral Region): 2/52 (3.8%) [16] and 6/60 (10%) [17] P. vivax infections; 3 Ebolowa (South Region): 3/60 (5%) P. vivax infections [16]; 4 Yaoundé (Centre Region): 1/29 (3.4%) P. vivax infection [16]; 5 Bertoua (East region): 2/25 (8%) P. vivax infections [16]; 6 Dschang (West Region): 27/484 (5.6%) P. vivax infections (present study)