Abstract
BackgroundThe Northern part of Senegal is characterized by a low and seasonal transmission of malaria. However, some Plasmodium falciparum infections and malaria clinical cases are reported during the dry season. This study aims to assess the relationship between IgG antibody (Ab) responses to gSG6-P1 mosquito salivary peptide and the prevalence of P. falciparum infection in children during the dry season in the Senegal River Valley. The positive association of the Ab response to gSG6-P1, as biomarker of human exposure to Anopheles vector bite, and P. falciparum infectious status (uninfected, infected-asymptomatic or infected-symptomatic) will allow considering this biomarker as a potential indicator of P. falciparum infection risk during the dry season.MethodsMicroscopic examination of thick blood smears was performed in 371 and 310 children at the start (January) and at the end (June) of the dry season, respectively, in order to assess the prevalence of P. falciparum infection. Collected sera were used to evaluate IgG response to gSG6-P1 by ELISA. Association between parasitological and clinical data (infected-asymptomatic or infected-symptomatic) and the anti-gSG6-P1 IgG levels were evaluated during this period.ResultsThe prevalence of P. falciparum infection was very low to moderate according to the studied period and was higher in January (23.5%) compared to June (3.5%). Specific IgG response was also different between uninfected children and asymptomatic carriers of the parasite. Children with P. falciparum infection in the dry season showed higher IgG Ab levels to gSG6-P1 than uninfected children.ConclusionsThe results strengthen the hypothesis that malaria transmission is maintained during the dry season in an area of low and seasonal transmission. The measurement of IgG responses to gSG6-P1 salivary peptide could be a pertinent indicator of human malaria reservoir or infection risk in this particular epidemiological context. This promising immunological marker could be useful for the evaluation of the risk of P. falciparum exposure observed during dry season and, by consequences, could be used for the survey of potential pre-elimination situation.
Highlights
The Northern part of Senegal is characterized by a low and seasonal transmission of malaria
The prevalence of P. falciparum infection was higher in January 2009 (23.5%) than in June 2009 (3.5%) (p < 0.001, Chi2 Test)
During the low-transmission season, P. falciparum infections were observed in the Northern Senegal River Valley
Summary
The Northern part of Senegal is characterized by a low and seasonal transmission of malaria. Malaria transmission in the Northern part of Senegal is low and occurs mainly between August and October due to a single rainy season from July to October [1] This situation creates breeding sites for two members of the Anopheles gambiae complex (An. gambiae s.s. and Anopheles arabiensis) and for Anopheles funestus, which breed in fresh water and in swampy habitats with much vegetation, respectively. In Northern Senegal, the construction of two dams on the Senegal River has enabled the enlargement of irrigated areas and the expansion of rice growing, providing breeding sites for mosquitoes. This situation could contribute to the maintenance of malaria transmission during the dry season [7]. The identification of P. falciparum carriers in human populations and the evaluation of their risks of exposure to malaria vectors are needed to carry out an effective malaria control in this particular area, considered suitable for malaria pre-elimination by the NMCP
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