Anopheles fauna of coastal Cayenne, French Guiana: modelling and mapping of species presence using remotely sensed land cover data

Little is known about the Anopheles species of the coastal areas of French Guiana, or their spatiotemporal distribution or environmental determinants. The present study aimed to (1) document the distribution of Anopheles fauna in the coastal area around Cayenne, and (2) investigate the use of remotely sensed land cover data as proxies of Anopheles presence. To characterise the Anopheles fauna, we combined the findings of two entomological surveys that were conducted during the period 2007-2009 and in 2014 at 37 sites. Satellite imagery data were processed to extract land cover variables potentially related to Anopheles ecology. Based on these data, a methodology was formed to estimate a statistical predictive model of the spatial-seasonal variations in the presence of Anopheles in the Cayenne region. Two Anopheles species, known as main malaria vectors in South America, were identified, including the more dominant An. aquasalis near town and rural sites, and An. darlingi only found in inland sites. Furthermore, a cross-validated model of An. aquasalis presence that integrated marsh and forest surface area was extrapolated to generate predictive maps. The present study supports the use of satellite imagery by health authorities for the surveillance of malaria vectors and planning of control strategies.

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

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.

Malaria on the Guiana Shield: a review of the situation in French Guiana

In a climate of growing concern that Plasmodium falciparum may be developing a drug resistance to artemisinin derivatives in the Guiana Shield, this review details our current knowledge of malaria and control strategy in one part of the Shield, French Guiana. Local epidemiology, test-treat-track strategy, the state of parasite drug resistance and vector control measures are summarised. Current issues in terms of mobile populations and legislative limitations are also discussed.

Incrimination of Anopheles (Anopheles) intermedius Peryassú, An. (Nyssorhynchus) nuneztovari Gabaldón, An. (Nys.) oswaldoi Peryassú as natural vectors of Plasmodium falciparum in French Guiana

Anopheles darlingi Root is the major vector of human malaria in the Neotropics and has been considered to be the sole malaria vector in French Guiana. The presence of other potential vectors suggests that malaria may be transmitted by other species under certain conditions. From 2006-2011, all anopheline specimens collected from 11 localities were assayed to determine if the Plasmodium circumsporozoite protein was present. In addition to An. darlingi, we found Anopheles oswaldoi, Anopheles intermedius and Anopheles nuneztovari specimens that were infected with Plasmodium sp. Further investigations on the behaviour and ecology of An. oswaldoi, An. intermedius and An. nuneztovari are necessary to determine their role in malaria transmission in French Guiana.

Multiple insecticide resistance in Aedes aegypti (Diptera: Culicidae) populations compromises the effectiveness of dengue vector control in French Guiana

In French Guiana, pyrethroids and organophosphates have been used for many years against Aedes aegypti. We aimed to establish both the resistance level of Ae. aegypti and the ultra low volume spray efficacy to provide mosquito control services with practical information to implement vector control and resistance management. Resistance to deltamethrin and fenitrothion was observed. In addition, the profound loss of efficacy of AquaK'othrine® and the moderate loss of efficacy of Paluthion® 500 were recorded. Fenitrothion remained the most effective candidate for spatial application in French Guiana until its removal in December 2010. Further investigation of the mechanism of resistance to deltamethrin demonstrated the involvement of mixed-function oxidases and, to a lesser extent, of carboxylesterases. However, these observations alone cannot explain the level of insecticide resistance we observed during tube and cage tests.

Anopheles darlingi bionomics and transmission of Plasmodium falciparum, Plasmodium vivax and Plasmodium malariae in Amerindian villages of the Upper-Maroni Amazonian forest, French Guiana

French Guiana is one of the areas in South America most affected by malaria and where the disease has become a serious public health problem. In spite of this situation, little recent entomological data are available from the main localities where the disease occurs, even though they are crucial for development of an effective vector control strategy. A longitudinal entomological survey was carried out from March 2000-February 2002 in three Amerindian villages, namely Twenké, Taluène and Cayodé, located in the Amazonian forest of the Upper-Maroni area, to assess anopheline mosquitoes and malaria transmission dynamics. Anopheles darlingi (Diptera: Culicidae) was the most abundant mosquito species caught during the study. This efficient American malaria vector was active the entire year, but showed an evident peak of abundance during the main rainfall season, from April-June, with an average human biting rate of 255.5 bites per person per night. Parity rates were homogeneous all year, indicating no significant seasonal variability in female survival rates. Estimated vectorial capacity indices were higher during the rainy season, even though the risk of transmission was present throughout the year (VCI > 1). A total of 14 An. darlingi were found infected with Plasmodium falciparum, Plasmodium vivax or Plasmodium malariae. The annual circumsporozoite indices were 0.15, 0.14 and 0.05, and the entomological inoculation rates were 22.8, 27.4 and 14.4 infected bites per person per year in Twenké, Taluène and Cayodé, respectively. An. darlingiwas endo-exophagic and rather exophilic in these localities. The species was collected throughout the night but was more aggressive between 21:30-03:30 h and after 05:30 h. Parity rates were homogeneous during the entire night. Impregnated hammock and/or bed nets, coupled with the use of mosquito repellents, as well as the early treatment of malarial cases, appear to be the most suitable tools for fighting...