Environmental, entomological, socioeconomic and behavioural risk factors for malaria attacks in Amerindian children of Camopi, French Guiana

Abstract

BackgroundMalaria is a major health issue in French Guiana. Amerindian communities remain the most affected. A previous study in Camopi highlighted the predominant role of environmental factors in the occurrence of malaria. However, all parameters involved in the transmission were not clearly identified. A new survey was conducted in order to clarify the risk factors for the presence of malaria cases in Camopi.MethodsAn open cohort of children under seven years of age was set up on the basis of biologically confirmed malaria cases for the period 2001-2009. Epidemiological and observational environmental data were collected using two structured questionnaires. Data were analysed with a multiple failures multivariate Cox model. The influence of climate and the river level on malaria incidence was evaluated by time-series analysis. Relationships between Anopheles darlingi human biting rates and malaria incidence rates were estimated using Spearman's rank correlation.ResultsThe global annual incidence over the nine-year period was 238 per 1,000 for Plasmodium falciparum, 514 per 1,000 for Plasmodium visa and 21 per 1,000 for mixed infections. The multivariate survival analysis associated higher malaria incidence with living on the Camopi riverside vs. the Oyapock riverside, far from the centre of the Camopi hamlet, in a home with numerous occupants and going to sleep late. On the contrary, living in a house cleared of all vegetation within 50 m and at high distance of the forest were associated with a lower risk. Meteorological and hydrological characteristics appeared to be correlated with malaria incidence with different lags. Anopheles darlingi human biting rate was also positively correlated to incident malaria in children one month later.ConclusionsMalaria incidence in children remains high in young children despite the appearance of immunity in children around three years of age. The closeness environment but also the meteorological parameters play an important role in malaria transmission among children under seven years of age in Camopi.

Mapping a Knowledge-Based Malaria Hazard Index Related to Landscape Using Remote Sensing: Application to the Cross-Border Area between French Guiana and Brazil

“…As in Stefani et al [46], the assumption is also made that the transmission is domiciliary, making it possible to link incidence rates to the dwellings and the environment features surrounding them; due to the small magnitude of the study area (15 km 2 ), the spatial disparity of the incidence rates cannot be explained by climatic and/or major environmental disparities in space; finally, the children in the cohort share similar immunity levels and genetic susceptibility to malaria transmission [10]. However, according to Stefani et al [10], the number of inhabitants in the home, the use of tropical repellents and domestic insecticides, the interventions of the county mosquito control services, and going to bed before 7:00 pm are protective factors against malaria transmission and can partially explain incidence rate disparities. In fact, we expect that the NLHI might predict the null or lower incidence rates with less accuracy than the higher ones, as the protective behaviors described above should make the incidence rates significantly lower, regardless of the landscape context.…”

“…and Stefani et al [10] for more details on this cohort). The P. falciparum incidence rates were computed for 28 of the 29 hamlets of the village of Camopi for the period of 2009-2013 (The P. falciparum incidence rates could not be computed for one hamlet because it did not include any children less than seven year old since 2009).…”

“…In Camopi, the annual incidence of malaria has exceeded 50% among children less than seven year old in the early 2000s [10], and has even reached 100% in 2006 [39]. From 2006 to 2012, the total number of reported malaria cases from Camopi and Trois-Sauts, a village in the municipality of Camopi, began to decrease, with a sharp reduction starting in 2009 [40,41].…”

“…All households in the village of Camopi were geolocalized with the global positioning system (GPS)-Magellan eXplorist™ 600-or by digitalization from the aerial photographs of BD-ORTHO ® [10,46]. For each NLHI candidate, the values were extracted for the locations of those households with at least one child less than seven year old included in the cohort, and then averaged at the hamlet level to explore the correlation between NLHI and P. falciparum incidence rates.…”

“…Moreover, the species shows a high efficiency in malaria transmission through high biting rates, susceptibility to Plasmodium infection and capacity to easily adapt to environmental changes due to human activities [5,9]. Natural and human-driven environmental changes, such as climate variability [10][11][12][13] and land use and land cover (LULC) changes [13][14][15][16][17][18][19], can determine the malaria distribution by influencing the habitats of adults and larvae. Prevention and treatment measures [20] and mobility of humans infected by Plasmodium [4,15] also influence such distribution.…”