Abstract
BackgroundMalaria elimination efforts can be undermined by imported malaria infections. Imported infections are classified based on travel history.MethodsA genetic strategy was applied to better understand the contribution of imported infections and to test for local transmission in the very low prevalence region of Richard Toll, Senegal.ResultsGenetic relatedness analysis, based upon molecular barcode genotyping data derived from diagnostic material, provided evidence for both imported infections and ongoing local transmission in Richard Toll. Evidence for imported malaria included finding that a large proportion of Richard Toll parasites were genetically related to parasites from Thiès, Senegal, a region of moderate transmission with extensive available genotyping data. Evidence for ongoing local transmission included finding parasites of identical genotype that persisted across multiple transmission seasons as well as enrichment of highly related infections within the households of non-travellers compared to travellers.ConclusionsThese data indicate that, while a large number of infections may have been imported, there remains ongoing local malaria transmission in Richard Toll. These proof-of-concept findings underscore the value of genetic data to identify parasite relatedness and patterns of transmission to inform optimal intervention selection and placement.
Highlights
Malaria elimination efforts can be undermined by imported malaria infections
Rapid diagnostic tests (RDTs) used to diagnose malaria cases detected through facility-based passive case detection (PCD) or during reactive case detection (RACD) were used to genotype all malaria infections
All individuals with RDT-positive malaria infection diagnosed at a health facility were followed up within 3 days by a community team that conducted detailed case investigation with RACD that involved visiting the index case household, where all individuals at least 6 months of age were tested by RDT, and the five closest neighbouring households
Summary
Malaria elimination efforts can be undermined by imported malaria infections. Imported infections are classified based on travel history. Senegal is characterized by distinct malaria transmission zones, ranging from very low in the North (incidence < 1/1000) to moderately high in the South (incidence > 400/1000). Understanding the risk and pattern of malaria transmission in a given geographical area provides the foundation for intervention selection and targeting to decrease malaria burden, eliminate transmission, and prevent re-establishment of malaria. The risk of malaria transmission is the product of the risk of local spread, rate of importation, and infectivity, and is referred to as the malariogenic potential [6]. The World Health Organization (WHO) recommends that these parameters inform the selection and targeting of interventions for eliminating malaria transmission [7]. Metrics that better identify and quantify the rate of importation and risk of local spread of malaria infections are required for successful malaria elimination
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