Genetic Evidence of FocalPlasmodium falciparumTransmission in a Pre-elimination Setting in Southern Province, Zambia

Abstract

Background. Southern Province, Zambia has experienced a dramatic decline in Plasmodium falciparum malaria transmission in the past decade and is targeted for elimination. Zambia's National Malaria Elimination Program recommends reactive case detection (RCD) within 140 m of index households to enhance surveillance and eliminate remaining transmission foci.Methods. To evaluate whether RCD captures local transmission, we genotyped 26 microsatellites from 106 samples collected from index (n = 27) and secondary (n = 79) cases detected through RCD in the Macha Hospital catchment area between January 2015 and April 2016.Results. Participants from the same RCD event harbored more genetically related parasites than those from different RCD events, suggesting that RCD captures, at least in part, infections related through local transmission. Related parasites clustered in space and time, up to at least 250 m from index households. Spatial analysis identified a putative focal transmission hotspot.Conclusions. The current RCD strategy detects focal transmission events, although programmatic guidelines to screen within 140 m of index households may fail to capture all secondary cases. This study highlights the utility of parasite genetic data in assessing programmatic interventions, and similar approaches may be useful to malaria elimination programs seeking to tailor intervention strategies to the underlying transmission epidemiology.

High genetic diversity of Plasmodium falciparum in the low transmission setting of the Kingdom of Eswatini

“…Samples were genotyped using microsatellite markers at 26 loci distributed across the P. falciparum genome [11,30,31] (Liu et al, in preparation). To minimize genotyping errors, strict thresholds were used to call alleles using a semi-supervised naïve Bayes classifier implemented in microSPAT software [32].…”

Spatial and genetic clustering of Plasmodium falciparum and Plasmodium vivax infections in a low-transmission area of Ethiopia

“…In this study, the prevalence and distribution of asymptomatic P. falciparum and P. vivax infections surrounding passively detected RDT-confirmed clinical malaria patients was assessed using RDT and quantitative PCR (qPCR) in Batu Degaga, Ethiopia. Spatial and temporal relatedness and clustering of infections within and between households of passively detected malaria infections and controls were investigated by genotyping 26 and 11 microsatellite loci for P. falciparum and P. vivax, respectively, which had been shown previously to be useful to describe population structure 12,[19][20][21][22][23][24][25] .…”

Confirmation of the absence of local transmission and geographic assignment of imported falciparum malaria cases to China using microsatellite panel

“…IBS was calculated based on the number of alleles shared between isolates, rather than of their haplotypes, allowing for the inclusion of mono-and poly-clonal samples. Pairwise IBS was determined as describe elsewhere [27,28]. Using this distance metric (1 -1/BS), a neighbor-joining tree and multidimensional scaling were calculated.…”