Spatial and temporal dynamics of malaria in Madagascar

Abstract

BackgroundMalaria is one of the primary health concerns in Madagascar. Based on the duration and intensity of transmission, Madagascar is divided into five epidemiological strata that range from low to mesoendemic transmission. In this study, the spatial and temporal dynamics of malaria within each epidemiological zone were studied.MethodsThe number of reported cases of uncomplicated malaria from 112 health districts between 2010 and 2014 were compiled and analysed. First, a Standardized Incidence Ratio was calculated to detect districts with anomalous incidence compared to the stratum-level incidence. Building on this, spatial and temporal malaria clusters were identified throughout the country and their variability across zones and over time was analysed.ResultsThe incidence of malaria increased from 2010 to 2014 within each stratum. A basic analysis showed that districts with more than 50 cases per 1000 inhabitants are mainly located in two strata: East and West. Lower incidence values were found in the Highlands and Fringe zones. The standardization method revealed that the number of districts with a higher than expected numbers of cases increased through time and expanded into the Highlands and Fringe zones. The cluster analysis showed that for the endemic coastal region, clusters of districts migrated southward and the incidence of malaria was the highest between January and July with some variation within strata.ConclusionThis study identified critical districts with low incidence that shifted to high incidence and district that were consistent clusters across each year. The current study provided a detailed description of changes in malaria epidemiology and can aid the national malaria programme to reduce and prevent the expansion of the disease by targeting the appropriate areas.Electronic supplementary materialThe online version of this article (10.1186/s12936-018-2206-8) contains supplementary material, which is available to authorized users.

Risk Factors for Malaria Infection in Central Madagascar: Insights from a Cross-Sectional Population Survey

“…[23][24][25][26] The status of, and risk factors associated with, the parasite reservoir in Madagascar were not previously described, despite a national commitment to shift from malaria case control toward parasite pre-elimination by 2022. 1 Madagascar's volatile malaria epidemiology, 2,3,27 which has seen important fluctuations likely to be associated with political and financial uncertainties since 2009, includes important epidemic outbreaks, 28 the causes of which remain poorly defined. 29 The cross-sectional population survey described here identified malaria infection in the western foothills of central Madagascar to be almost exclusively asymptomatic and submicroscopic.…”

Variation in Anopheles distribution and predictors of malaria infection risk across regions of Madagascar

“…The overlap between larval sampling and RDT testing in the SE and SW differed by up to five and up to three months, respectively. The peak transmission period in these regions has been found to be from January to May or June [20], so all larvae were collected during the peak transmission season for each region. Thus, it is not expcted that the mismatched sampling times would bias the results (For further seasonal analysis, see Additional file 2: Table S2).…”

“…Nationally, large-scale anthropogenic deforestation and land-use change are widespread [13][14][15][16]; 63% of Madagascar's population of 26,262,368 lives in small farming communities in rural areas [17]. However, the distribution of land-use change rates, known malaria risk factors, and malaria prevalence patterns vary regionally in Madagascar [18][19][20][21]. Communities living in the central highlands, for example, experience unstable transmission and low prevalence coupled with a history of intense forest clearance and actively cultivated landscapes [16,22].…”

Variation in Anopheles distribution and predictors of malaria infection risk across regions of Madagascar

“…The overlap between larval sampling and RDT testing in the SE and SW differed by up to ve and up to three months, respectively. The peak transmission period in these regions has been found to be from January to May or June (20), so all larvae were collected during the peak transmission season for each region. Thus, we would not expect the mismatched sampling times to bias our results (For further seasonal analysis, see ESM2 Table 2).…”