Genetic evidence for imported malaria and local transmission in Richard Toll, Senegal

Abstract

Background: Malaria elimination efforts can be undermined by imported malaria infections. Imported infections are classified based on travel history.Methods: We applied a genetic strategy to better understand the contribution of imported infections and to test for local transmission in the very low prevalence region of Richard Toll, Senegal.Results: Genetic 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-travelers compared to travelers.Conclusions: These 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. This work was supported by the Bill & Melinda Gates Foundation, Grant Number OPP1156051

Modeling the levels, trends, and connectivity of malaria transmission using genomic data from a health facility in Thiès, Senegal

“…Malaria parasite molecular data have been utilized for a wide set of research and programmatic questions beyond drug and diagnostic resistance detection. Molecular data enables the identification of different malaria species [9, 10] providing especially helpful information in regions where malaria infections were either absent or considered completely imported [11]. An extensive library of parasite genetic samples can also help researchers and programmatic investigators during an out-break to help determine the geographic origin, rate of importation, and subsequent level of local transmission [12, 13, 11].…”

“…Molecular data enables the identification of different malaria species [9, 10] providing especially helpful information in regions where malaria infections were either absent or considered completely imported [11]. An extensive library of parasite genetic samples can also help researchers and programmatic investigators during an out-break to help determine the geographic origin, rate of importation, and subsequent level of local transmission [12, 13, 11]. More broadly, genetic similarity between samples has been used to identify the parasite connectivity between human populations [14, 15, 16, 17, 18, 19], which may provide a pragmatic and cost-effective tool to inform control programs as they plan local elimination efforts [20].…”

Plasmodium falciparum genomic surveillance reveals spatial and temporal trends, association of genetic and physical distance, and household clustering

“…Unscheduled visits in which study subjects had Re-infected participants were all from the same household (MS). Parasite genotypes from the first infection were genetically distinct from the re-infected parasites ( Figure 4), and three of them (U5, U6 and U7) represented genotypes which had not been previously described, either in Thiès or in multiple regions of Senegal from 2006-present 14,16,21 .…”

“…Having such different parasites in the same household could be the result of a hotspot of local intense transmission 17 , coupled with genetic recombination (outcrossing) within the Anopheles mosquito 26 , and the subsequent transmission of new genetic combinations 17 . An alternative could be the importation of diverse genotypes due to human or mosquito mobility 21,[27][28][29][30] . A similar study of malaria incidence and prevalence has demonstrated the existence of malaria transmission hotspots at the village level in Senegal 7,8 .…”