Abstract
Background In December 2010, a Plasmodium vivax malaria outbreak occurred among French forces involved in a mission to control illegal gold mining in French Guiana. The findings of epidemiological and entomological investigations conducted after this outbreak are presented here.MethodsData related to malaria cases reported to the French armed forces epidemiological surveillance system were collected during the epidemic period from December 2010 to April 2011. A retrospective cohort study was conducted to identify presumed contamination sites. Anopheles mosquitoes were sampled at the identified sites using Mosquito Magnet and CDC light traps. Specimens were identified morphologically and confirmed using molecular methods (sequencing of ITS2 gene and/or barcoding). Anopheles infections with Plasmodium falciparum and P. vivax were tested by both enzyme-linked immunosorbent assay and real-time PCR.ResultsSeventy-two P. vivax malaria cases were reported (three were mixed P. falciparum/P. vivax infections), leading to a global attack rate of 26.5 % (72/272). Lack of compliance with vector control measures and doxycycline chemoprophylaxis was reported by patients. Two illegal gold mining sites located in remote areas in the primary forest were identified as places of contamination. In all, 595 Anopheles females were caught and 528 specimens were formally identified: 305 Anopheles darlingi, 145 Anopheles nuneztovari s.l., 63 Anopheles marajoara and 15 Anopheles triannulatus s.l. Three An. darlingi were infected by P. falciparum (infection rate: 1.1 %) and four An. marajoara by P. vivax (infection rate: 6.4 %).DiscussionThe main drivers of the outbreak were the lack of adherence by military personnel to malaria prevention measures and the high level of malaria transmission at illegal gold mining sites. Anopheles marajoara was clearly implicated in malaria transmission for the first time in French Guiana. The high infection rates observed confirm that illegal gold mining sites must be considered as high level malaria transmission areas in the territory.ConclusionsIllegal gold mining activities are challenging the control of malaria in French Guiana. Collaboration with neighbouring countries is necessary to take into account mobile populations such as gold miners. Malaria control strategies in the French armed forces must be adapted to P. vivax malaria and sylvatic Anopheles species.
Highlights
In December 2010, a Plasmodium vivax malaria outbreak occurred among French forces involved in a mission to control illegal gold mining in French Guiana
Illegal gold mining activities are challenging the control of malaria in French Guiana
Malaria control strategies in the French armed forces must be adapted to P. vivax malaria and sylvatic Anopheles species
Summary
French Guiana is a French overseas entity and an Outermost Region of the European Union located on the northeast coast of South America (Fig. 1) It is a sparsely populated area—250,000 inhabitants in 2013—and 85 % of the territory is covered by the Amazon rainforest [1]. From 2005 to 2014, the number of malaria cases officially reported in French Guiana (all Plasmodium species) decreased from 4479 to 445 [3] Most of these officially-reported cases currently occur in villages located along the main rivers flowing through the territory, especially those bordering Suriname and Brazil [3]. This is partially offset by an increase in the number of cases related to transmission at illegal gold mining sites. Such sites located in forested inland French Guiana are probably areas of malaria transmission for Plasmodium vivax, Plasmodium falciparum and Plasmodium malariae [4,5,6,7]
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