Unexpected high circulation of Plasmodium vivax in asymptomatic children from Kédougou, southeastern Senegal

Abstract

BackgroundMalaria in Senegal is due essentially to infections by Plasmodium falciparum and, to a lesser extent to Plasmodium malariae and Plasmodium ovale. By the use of molecular methods, detection of Plasmodium vivax has been recently reported in the region of Kedougou, raising the question of appraisal of its potential prevalence in this setting.MethodsA retrospective serological study was carried out using 188 samples taken from 2010 to 2011 in a longitudinal school survey during which 48 asymptomatic children (9–11 years) were recruited. Four collections of samples collected during two successive dry and rainy seasons were analysed for antibody responses to P. vivax and P. falciparum. Recombinant P. falciparum and P. vivax MSP1 antigens and total P. falciparum schizont lysate from African 07/03 strain (adapted to culture) were used for ELISA. Nested PCR amplification was used for molecular detection of P. vivax.ResultsA surprising high prevalence of IgG responses against P. vivax MSP1 was evidenced with 53% of positive samples and 58% of the individuals that were found positive to this antigen. There was 77% of responders to P. falciparum outlined by 63% of positive samples. Prevalence of responders did not differ as function of seasons. Levels of antibodies to P. falciparum fluctuated with significant increasing between dry and rainy season (P < 0.05), contrary to responses to P. vivax. There was a significant reciprocal relationship (P < 10−3) between antibody responses to the different antigens, but with weak coefficient of correlation (Rho around 0.3) underlining a variable profile at the individual level. Clear molecular signature was found in positive IgG to P. vivax msp1 samples by PCR.ConclusionThis cross-sectional longitudinal study highlights the unexpected high circulation of P. vivax in this endemic area. Sero-immunology and molecular methods are powerful additive tools to identify endemic sites where relevant control measures have to be settled and monitored.

Presence of additionalP. vivaxmalaria in Duffy negative individuals from Southwestern Nigeria

“…https://doi.org/10.1101/19009837 doi: medRxiv preprint (100% similarity) with their references as expected (Figur 2-for P. vivax and supplementary Figures 1, 2 and 3). This is not unexpected as cases of P. vivax have been identified in many countries in sSA (3)(4)(5)29,33,(39)(40)(41)(42) including Nigeria (6), where it was thought to be absent due to the non-expression of the DARC gene on the RBC of majority of the population.Thus, this is adding to the growing evidence of the proposed gradual incursion of P. vivax into sSA sub-region (data unpublished). The identification of more P. 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.…”

“…In some of these studies, such as in those conducted in Angola, Cameroon , Kenya, Madagascar, Mali and Mauritania, the Duffy status of the infected individuals was characterized and they were found to be mostly Duffy negative (3,4,(27)(28)(29)(30). In others, however, the investigators just stopped at identification of P. vivax without stating the Duffy status of the infected individuals (5,(31)(32)(33). Interestingly, all studies were carried out amongst indigenous individuals with little or no travel history to vivax endemic areas, ruling out the possibility of imported infection.…”

Analysis of anti-Plasmodium IgG profiles among Fulani nomadic pastoralists in northern Senegal to assess malaria exposure

“…In Mali, where P. vivax was considered absent, recent studies have indicated its presence in the country [40]. A recent study showed an unexpectedly high seroprevalence of P. vivax in a small sample of asymptomatic children from Kédougou in the southeastern Senegal, with a seroprevalence of 58% by ELISA [41]. Additional investigations are needed to provide clearer information, as the presence of P. vivax, especially in the northern areas where the NMCP is conducting pre-elimination strategies for malaria, would require diagnostic tools capable of detecting non-falciparum malaria and mixed infections, as well as updated treatment recommendations for non-falciparum malaria.…”

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

“…In sub-Saharan Africa (sSA), majority (99%) of the infections is thought to be due to Plasmodium falciparum and rarely by P. ovale, P. malariae, with P. vivax not even being considered in the picture as one of the players [1] of malaria infection. With the availability of tools that are more sensitive, the detection of non-falciparum and even vivax human malaria parasites has gained more attention in sSA [2][3][4][5][6].…”

“…In some of these studies, such as in those conducted in Angola, Cameroon, Kenya, Madagascar, Mali and Mauritania, the Duffy status of the infected individuals was characterized and they were found to be mostly Duffy negative [3,4,[27][28][29][30]. In others, however, the investigators were concerned with the identification of P. vivax without stating the Duffy status of the infected individuals [5,[31][32][33]. Interestingly, all studies were carried out amongst indigenous individuals with little or no travel history to vivax endemic areas, thus ruling out the possibility of imported infection.…”