High malaria transmission in a forested malaria focus in French Guiana: How can exophagic Anopheles darlingi thwart vector control and prevention measures?

Samuel B Vezenegho,Isabelle Dusfour,Sébastien Briolant,Romain Girod,Antoine Adde,Jean Issaly,Vincent Pommier De Santi,Romuald Carinci,Pascal Gaborit

doi:10.1590/0074-02760160150

Abstract

In French Guiana, malaria vector control and prevention relies on indoor residual spraying and distribution of long lasting insecticidal nets. These measures are based on solid epidemiological evidence but reveal a poor understanding of the vector. The current study investigated the behaviour of both vectors and humans in relation to the ongoing prevention strategies. In 2012 and 2013, Anopheles mosquitoes were sampled outdoors at different seasons and in various time slots. The collected mosquitoes were identified and screened for Plasmodium infection. Data on human behaviour and malaria episodes were obtained from an interview. A total of 3,135 Anopheles mosquitoes were collected, of which Anopheles darlingi was the predominant species (96.2%). For the December 2012-February 2013 period, the Plasmodium vivax infection rate for An. darlingi was 7.8%, and the entomological inoculation rate was 35.7 infective bites per person per three-month span. In spite of high bednet usage (95.7%) in 2012 and 2013, 52.2% and 37.0% of the participants, respectively, had at least one malaria episode. An. darlingi displayed heterogeneous biting behaviour that peaked between 20:30 and 22:30; however, 27.6% of the inhabitants were not yet protected by bednets by 21:30. The use of additional individual and collective protective measures is required to limit exposure to infective mosquito bites and reduce vector densities.

Highlights

A total of 24 anopheline species have been reported in French Guiana (Talaga et al 2015)
Distribution and human biting rates (HBR) of Anopheles species collected in Blondin village, Saint-Georges de l’Oyapock municipality, French Guiana, using human landing catches from
The current study was designed to unravel malaria transmission mechanisms and to determine whether the currently implemented malaria vector control strategies are tailored to the behaviour of the main vectors

Summary

Introduction

A total of 24 anopheline species have been reported in French Guiana (Talaga et al 2015) One of these is Anopheles (Nyssorhynchus) darlingi, known as the most common malaria vector in the Americas and, in the Amazon Region (Sinka et al 2010, Hiwat & Bretas 2011, Laporta et al 2015). In French Guiana, this species has been collected while biting humans outside houses in both the coastal region and in forested areas (Pajot et al 1977, Girod et al 2008, Dusfour et al 2010, 2013, Vezenegho et al 2014, 2015) These entomological observations should be considered in the light of human behaviour to define an efficient and sustainable malaria vector control strategy.

Methods

Results

Conclusion