GSG6-P1 salivary biomarker discriminates micro-geographical heterogeneity of human exposure to Anopheles bites in low and seasonal malaria areas

André Barembaye Sagna,Lobna Gaayeb,Papa Makhtar Drame,Jean Biram Sarr,Modou Seck,Emmanuel Hermann,Anne-Marie Schacht,Cheikh Sokhna,Cheikh Saya Sow,Ngor Faye,Simon Senghor,Anne Poinsignon,Mamadou Ousmane Ndiath,Gilles Riveau,Franck Remoue

doi:10.1186/1756-3305-6-68

Abstract

BackgroundOver the past decade, a sharp decline of malaria burden has been observed in several countries. Consequently, the conventional entomological methods have become insufficiently sensitive and probably under-estimate micro-geographical heterogeneity of exposure and subsequent risk of malaria transmission. In this study, we investigated whether the human antibody (Ab) response to Anopheles salivary gSG6-P1 peptide, known as a biomarker of Anopheles exposure, could be a sensitive and reliable tool for discriminating human exposure to Anopheles bites in area of low and seasonal malaria transmission.MethodsA multi-disciplinary survey was performed in Northern Senegal where An. gambiae s.l. is the main malaria vector. Human IgG Ab response to gSG6-P1 salivary peptide was compared according to the season and villages in children from five villages in the middle Senegal River valley, known as a low malaria transmission area.ResultsIgG levels to gSG6-P1 varied considerably according to the villages, discriminating the heterogeneity of Anopheles exposure between villages. Significant increase of IgG levels to gSG6-P1 was observed during the peak of exposure to Anopheles bites, and decreased immediately after the end of the exposure season. In addition, differences in the season-dependent specific IgG levels between villages were observed after the implementation of Long-Lasting Insecticidal Nets by The National Malaria Control Program in this area.ConclusionThe gSG6-P1 salivary peptide seems to be a reliable tool to discriminate the micro-geographical heterogeneity of human exposure to Anopheles bites in areas of very low and seasonal malaria transmission. A biomarker such as this could also be used to monitor and evaluate the possible heterogeneous effectiveness of operational vector control programs in low-exposure areas.

Highlights

Over the past decade, a sharp decline of malaria burden has been observed in several countries
The present study aims to assess if the gSG6-P1 salivary peptide could be a sensitive tool for discriminating human exposure to An. gambiae bites in a micro-geographical context of low and seasonal malaria transmission
Entomological and parasitological data Previous results indicated that malaria transmission in the study villages was low and seasonal with an EIR ranging from 0 to 0.059 [35]

Summary

Introduction

A sharp decline of malaria burden has been observed in several countries. The intensity of exposure to Anopheles bites, and the risk of malaria transmission, may be different from a local setting to another within a single micro-geographical region [5,6,7] and even between neighbouring villages or houses [8] This heterogeneity of exposure to Anopheles is important in areas of low malaria transmission, where only few infected mosquitoes are sampled and where focal hotspots of malaria transmission may exist [9]. The evaluation of the real exposure to Anopheles, and the risk of malaria transmission by the EIR, seems irrelevant and not adapted in these contexts because the number of collected mosquitoes are often below the detection limits of commonly used trapping methods [7,9] It has been shown there is significant malaria transmission in the Senegal River Basin, yet entomological data showed a very low exposure to Anopheles bites [12,13]. Those tools could be useful for targeting areas where the control should be strengthened

Methods

Results

Discussion

Conclusion