Exploring the heterogeneity of human exposure to malaria vectors in an urban setting, Bouaké, Côte d’Ivoire, using an immuno-epidemiological biomarker

Abstract

BackgroundIn some African cities, urban malaria is a threat to the health and welfare of city dwellers. To improve the control of the disease, it is critical to identify neighbourhoods where the risk of malaria transmission is the highest. This study aims to evaluate the heterogeneity of malaria transmission risk in one city (Bouaké) in a West African country (Côte d’Ivoire) that presents several levels of urbanization.MethodsTwo cross-sectional studies were conducted in three neighbourhoods (Dar-es-Salam, Kennedy and N’gattakro) in Bouaké during both the rainy and dry seasons. Data on insecticide-treated net (ITN) use and blood samples were collected from children aged between 6 months and 15 years to determine the parasite density and the prevalence of Plasmodium falciparum and the level of IgG against the Anopheles gSG6-P1 salivary peptide, used as the biomarker of Anopheles bite exposure.ResultsThe specific IgG levels to the gSG6-P1 salivary peptide in the rainy season were significantly higher compared to the dry season in all neighbourhoods studied (all p < 0.001). Interestingly, these specific IgG levels did not differ between neighbourhoods during the rainy season, whereas significant differences in IgG level were observed in the dry season (p = 0.034). ITN use could be a major factor of variation in the specific IgG level. Nevertheless, no difference in specific IgG levels to the gSG6-P1 salivary peptide was observed between children who declared “always” versus “never” sleeping under an ITN in each neighbourhood. In addition, the prevalence of P. falciparum in the whole population and immune responders was significantly different between neighbourhoods in each season (p < 0.0001).ConclusionThis study highlights the high risk of malaria exposure in African urban settings and the high heterogeneity of child exposure to the Anopheles vector between neighbourhoods in the same city. The Anopheles gSG6-P1 salivary peptide could be a suitable biomarker to accurately and quantitatively assess the risk of malaria transmission in urban areas.Electronic supplementary materialThe online version of this article (10.1186/s12936-019-2696-z) contains supplementary material, which is available to authorized users.

Preliminary validation of the use of IgG antibody response to Anopheles gSG6-p1 salivary peptide to assess human exposure to malaria vector bites in two endemic areas of Cameroon in Central Africa

“…This data suggest the use of this specific antibody response to gSG6-P1 peptide as a pertinent marker to assess human exposure to Anopheles mosquitoes in Cameroon. This finding is similar to those reported in other regions in Africa [ 23 – 29 , 33 , 34 , 36 – 40 ], Americas [ 30 ] and Asia [ 31 , 32 ],where it was shown that the IgG response to the saliva peptide was associated to the level of exposure to mosquito bites [ 25 , 27 , 28 , 30 , 37 ] and to malaria infectious status [ 23 , 32 , 40 ]. Together, our data and from these previous studies confirm the relevance of this candidate biomarker to be used to assess human exposure to malaria vectors worldwide.…”

“…More specifically, IgG antibody response to the gSG6-P1 salivary peptide ( An . gambiae Salivary Gland Protein-6 peptide 1) has been validated as a relevant biomarker of Anopheles bites in various settings including West and East Africa [ 23 – 29 ], America [ 30 ] and Asia [ 31 , 32 ]. Moreover, in Africa, antibody response to gSG6-P1 salivary peptide was also found relevant for detecting human exposure to malaria vectors in the context of low and seasonal mosquito densities [ 24 , 26 , 27 – 29 ].…”

“…gambiae Salivary Gland Protein-6 peptide 1) has been validated as a relevant biomarker of Anopheles bites in various settings including West and East Africa [ 23 – 29 ], America [ 30 ] and Asia [ 31 , 32 ]. Moreover, in Africa, antibody response to gSG6-P1 salivary peptide was also found relevant for detecting human exposure to malaria vectors in the context of low and seasonal mosquito densities [ 24 , 26 , 27 – 29 ]. Interestingly, immune specific response to this biomarker was reported to be a pertinent tool to assess the efficacy of malaria vector control strategies in several countries in West and East Africa [ 24 , 33 , 34 ].…”

Pattern of antibody responses to Plasmodium falciparum antigens in individuals differentially exposed to Anopheles bites

“…gambiae Salivary Gland Protein-6 peptide 1) of An. gambiae saliva has been identified and validated as a pertinent biomarker of Anopheles bites [36][37][38]. It represents a proxy of human exposure to Anopheles bites and is a reliable tool for assessing spatial and temporal heterogeneity of exposure at the individual level [35].…”

Spatial Assessment of Contact Between Humans and Anopheles and Aedes Mosquitoes in a Medium-Sized African Urban Setting, Using Salivary Antibody–Based Biomarkers

“…Furthermore, hot spots of Anopheles bite exposure inside neighborhoods were located in the northern part of GND and NDI and in the southern part of PSD. The presence of these hot spots could be explained by several individual and/or household factors, distance from breeding sites [43], and vegetation cover [44]. For instance, the particularly low dispersion of adult mosquitoes in urban areas could lead to high exposure among children living near Anopheles breeding sites, compared with exposure among those who live further away [36,45,46].…”