Epidemiological and entomological studies of a malaria outbreak among French armed forces deployed at illegal gold mining sites reveal new aspects of the disease’s transmission in French Guiana

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.

Identification of French Guiana anopheline mosquitoes by MALDI-TOF MS profiling using protein signatures from two body parts

“…Anopheles adult female mosquitoes were selected from field mosquito collections done in 6 distinct sites from French Guiana, during entomological surveys, using different collection methods, over different sampling periods (Figure 1) [3,39–41]. After collections, mosquitoes were sorted by genera and Anopheles mosquitoes were morphologically identified under a binocular loupe at a magnification of ×56 (Leica M80, Leica, Nanterre, France) using standard taxonomic keys for the region (Floch and Abonnenc 1951, Forattini 1962, Faran and Linthicum 1981).…”

Contribution of the French army health service in support of expertise and research in infectiology in Africa

“…Vector-borne diseases constitute a major threat to the operational capacity of armed forces personnel operating outside or stationed overseas. In past years, the military health service participated in monitoring the entomologic status of French military bases in sub-Saharan Africa (Gabon, Ivory Coast, Republic of Central Africa, Senegal, Djibouti) and focused on French Guiana [2] , [3] , [4] , [5] , [6] , [7] , [8] . This surveillance included the identification of vectors, the study of behaviour and the evaluation of insecticide resistance and enabled the development or improvement of new tools for vector trapping [9] , [10] , vector identification such as molecular and proteomic methods [11] , [12] , pathogen identification in vectors [13] , [14] or identification of markers of resistance to insecticides [2] , [3] .…”

“…In order to better characterize the risk of naturally acquired infections, epidemiologic studies are conducted in French armies and their neighbourhood. For example, investigations have been conducted after the occurrence of malaria outbreaks among French forces involved in missions to control illegal gold mining in French Guiana [7] . The epidemiologic and entomologic studies conducted in these remote and dangerous areas have demonstrated that illegal gold mining sites must be considered to be high-level malaria transmission areas.…”

Dynamical Mapping of Anopheles darlingi Densities in a Residual Malaria Transmission Area of French Guiana by Using Remote Sensing and Meteorological Data

“…Plasmodium vivax is the predominant malaria parasite species and was responsible for 80% of the diagnosed cases in 2015, with the remainder mainly due to P . falciparum [ 21 – 24 ]. Most malaria cases are reported in villages located along the main rivers flowing through the territory and in illegal gold mining areas, which are propitious places for malaria transmission [ 23 – 25 ].…”