Deforestation, agriculture and farm jobs: a good recipe for Plasmodium vivax in French Guiana

BackgroundMalaria risk can vary markedly between households in the same village, or between villages, but the determinants of this “micro-epidemiological” variation in malaria risk remain poorly understood. This study aimed to identify factors that explain fine-scale variation in malaria risk across settings and improve definitions and methods for malaria micro-epidemiology.MethodsA systematic review of studies that examined risk factors for variation in malaria infection between individuals, households, clusters, hotspots, or villages in any malaria-endemic setting was conducted. Four databases were searched for studies published up until 6th October 2015. Crude and adjusted effect estimates for risk factors for malaria infection were combined in random effects meta-analyses. Bias was assessed using the Newcastle–Ottawa Quality Assessment Scale.ResultsFrom 743 retrieved records, 51 studies were selected, representing populations comprising over 160,000 individuals in 21 countries, in high- and low-endemicity settings. Sixty-five risk factors were identified and meta-analyses were conducted for 11 risk factors. Most studies focused on environmental factors, especially increasing distance from a breeding site (OR 0.89, 95% CI 0.86–0.92, 10 studies). Individual bed net use was protective (OR 0.63, 95% CI 0.52–0.77, 12 studies), but not household bed net ownership. Increasing household size (OR 1.08, 95% CI 1.01–1.15, 4 studies) and household crowding (OR 1.79, 95% CI 1.48–2.16, 4 studies) were associated with malaria infection. Health seeking behaviour, medical history and genetic traits were less frequently studied. Only six studies examined whether individual-level risk factors explained differences in malaria risk at village or hotspot level, and five studies reported different risk factors at different levels of analysis. The risk of bias varied from low to high in individual studies. Insufficient reporting and comparability of measurements limited the number of meta-analyses conducted.ConclusionsSeveral variables associated with individual-level malaria infection were identified, but there was limited evidence that these factors explain variation in malaria risk at village or hotspot level. Social, population and other factors may confound estimates of environmental risk factors, yet these variables are not included in many studies. A structured framework of malaria risk factors is proposed to improve study design and quality of evidence in future micro-epidemiological studies.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-017-1792-1) contains supplementary material, which is available to authorized users.

Section: Resultsmentioning

confidence: 99%

Defining micro-epidemiology for malaria elimination: systematic review and meta-analysis

Bannister-Tyrrell

Verdonck

Hausmann-Muela³

et al. 2017

“…Therefore, the question remains whether symptomatic or asymptomatic cases are the main reservoir of the P. falciparum parasite in a low-endemic Southeast Asian malaria setting. For P. vivax , there has been less effort in identifying transmission hotspots, and as far as we know, all but one [ 15 ] spatial and temporal analyses have been restricted to symptomatic or microscopically confirmed cases [ 16 – 25 ]. Spatial heterogeneity of symptomatic vivax malaria has been linked to environmental disturbances [ 16 , 18 ], distance to breeding sites [ 16 , 17 ], soil occupation [ 19 , 26 ], or forest coverage [ 18 ].…”

Section: Introductionmentioning

confidence: 99%

Identification and characterization of areas of high and low risk for asymptomatic malaria infections at sub-village level in Ratanakiri, Cambodia

Durnez

Pareyn

Mean

et al. 2018

BackgroundMalaria elimination needs a concentration of activities towards identification of residual transmission foci and intensification of efforts to eliminate the last few infections, located in so-called ‘malaria hotspots’. Previous work on characterizing malaria transmission hotspots has mainly focused on falciparum malaria and especially on symptomatic cases, while the malaria reservoir is expected to be mainly concentrated in the asymptomatic human population when transmission is low. For Plasmodium vivax, there has been less effort in identifying transmission hotspots. The main aim of this study was to uncover micro-epidemiological mechanisms of clustering of malaria infections at a sub-village level, based on geographical or behavioural features.MethodsA cross-sectional survey was performed in three villages within the highest malaria endemic province of Cambodia. The survey took place in the dry season, when the malaria reservoir is expected to be low and residing in the asymptomatic part of the population. Village and field locations of households were georeferenced, blood samples were taken from as many residents as possible and a short questionnaire probing for individual risk factors was taken. Asymptomatic malaria carriers were detected by PCR, and geographical clustering analysis (SaTScan) as well as risk factor analysis were performed.ResultsA total of 1540 out of 1792 (86%) individuals were sampled. Plasmodial DNA was detected in 129 individuals (8.4%). P. vivax was most prevalent (5.5%) followed by Plasmodium malariae (2.1%) and Plasmodium falciparum (1.6%). Mixed infection occurred in 12 individuals. In two out of three villages geographical clustering of high and low malaria infection risk was clearly present. Cluster location and risk factors associated with the infection differed between the parasite species. Age was an important risk factor for the combined Plasmodium infections, while watching television at evenings was associated with increased odds of P. vivax infections [OR (CI): 1.86 (0.95–3.64)] and bed net use was associated with reduced odds of P. falciparum infections [OR (CI): 0.25 (0.077–0.80)].ConclusionsClusters of malaria carriers were malaria species specific and often located remotely, outside village centres. As such, at micro-epidemiological level, malaria is not a single disease. Further unravelling the micro-epidemiology of malaria can enable programme managers to define the interventions likely to contribute to halt transmission in a particular hotspot location.Electronic supplementary materialThe online version of this article (10.1186/s12936-017-2169-1) contains supplementary material, which is available to authorized users.

“…In Latin America but French Guiana, primaquine is prescribed for every patient infected with P. vivax without looking for G6PDd or ethnicity assignment [ 17 ]. In French Guiana, P. vivax has become the dominant malaria species with more than 60 % of attacks with a substantial increase of cases since mid-2001, mostly observed in children [ 18 ], Amerindian populations [ 19 ], gold panners, French armed forces [ 20 ], Hmong [ 21 ], and to a lesser extent, in the Noir Marron community [ 22 ]. Most of the malaria transmission occurs along the two frontier rivers.…”

Section: Introductionmentioning

confidence: 99%

Sub-Saharan red cell antigen phenotypes and glucose-6-phosphate dehydrogenase deficiency variants in French Guiana

Petit

Bailly

Chiaroni

et al. 2016

Background The treatment of Plasmodium vivax infections requires the use of primaquine, which can lead to severe haemolysis in glucose-6-phosphate dehydrogenase (G6PD)-deficient individuals. However, most of the Latin American countries, which are still endemic for vivax malaria, lack information on the distribution of G6PD deficiency (G6PDd). No survey has been performed so far in French Guiana. Herein, 80 individuals of the French Guianan Noir Marron population were scrutinized for red cell surface antigens of six blood group systems (ABO, Rh, Kell, Kidd, Duffy and MNS) and G6PD genetic polymorphisms. First, the sub-Saharan origin of the red cell phenotypes was assessed in relation with the literature. Then, given that the main sub-Saharan G6PDd variants are expected to be encountered, only the G6PD sequences of exons 4, 5, 6 and 9 were screened. This work aims at appraising the G6PD gene variation in this population, and thus, contributing to the G6PD piecemeal information in Latin America.ResultsNinety-seven percent (97 %) of the red cells are Fy(a− b−), either D+ C− E− c+ e+ or D+ C+ E− c+ e+ and 44 % exhibited the Fya−/Jkb−/S− combined phenotype. Noteworthy is the detection of the G6PD(Val68Met) variant characterized by c.202G > A transition, G6PD(Asn126Asp) variant characterized by c.376A>G transition and G6PD(Asp181Val) variant characterized by c.542A>T transversion of the G6PD gene in 22.5 % of the sample, characteristic of the A−(202), A and Santamaria G6PDd variants, respectively.ConclusionsFrench Guianan Noir Marron population represents a pool of Rh-D antigen positive, Duffy-negative and G6PD-deficient erythrocytes, the latter accounting for one in every eight persons. The present study provides the first community-based estimation of the frequency of G6PDd polymorphisms in French Guiana. These results contribute to the G6PD genetic background information puzzle in Latin America.