Abstract
With support from the Global Fund, the United States President's Malaria Initiative (PMI) and other cooperating partners, Malawi is implementing a comprehensive malaria control programme involving indoor residual spraying in targeted districts, universal coverage with insecticide-treated bed nets, use of rapid diagnostic tests to confirm the clinical diagnosis of malaria and use of the highly effective artemisinin-based combination therapy, artemether-lumefantrine (AL), as the first-line treatment for malaria. We genotyped 24 genome-wide single nucleotide polymorphisms (SNPs) in Plasmodium falciparum infections (n=316) sampled from a single location in Malawi before (2006 and 2007) and after enhanced intervention (2008 and 2012). The SNP data generated were used to examine temporal changes in the proportion of multiple-genotype infections (MIs), mean number of heterozygous SNPs within MIs, parasite genetic diversity (expected heterozygosity and genotypic richness), multilocus linkage disequilibrium and effective population size (Ne). While the proportion of MIs, expected heterozygosity, genotypic richness, multilocus linkage disequilibrium and Ne were unchanged over time, the mean number (±standard deviation) of heterozygous SNPs within MIs decreased significantly (p=0.01) from 9(±1) in 2006 to 7(±1) in 2012. These findings indicate that the genetic diversity of P. falciparum malaria parasites in this area remains high, suggesting that only subtle gains, if any, have been made in reducing malaria transmission. Continued surveillance is required to evaluate the impact of malaria control interventions in this area and the rest of Malawi, and to better target control interventions.
Highlights
Malaria-endemic countries are rapidly scaling up malaria control interventions to reduce the burden of malaria
We might expect to see significant reductions in malaria transmission partly because, unlike SP, which has weak activity against transmissible stages of the parasite, AL is highly active against both asexual parasites and gametocytes (Okell et al, 2008; Sutherland et al, 2005)
We successfully genotyped 295 out of 316 parasite infections sampled from children less than 5 years old presenting to Ndirande Health Centre with uncomplicated P. falciparum malaria before and after enhanced intervention
Summary
Malaria-endemic countries are rapidly scaling up malaria control interventions to reduce the burden of malaria. This has led to significant reductions in the numbers of malaria cases and malaria-related deaths in several countries (Chizema-Kawesha et al, 2010; O’meara et al, 2010; World Health Organization, 2013a, T.J. Sisya et al / Acta Tropica 142 (2015) 108–114 are limited and conflicting data on the impact of this programme. While some reports indicate a significant decrease in malaria burden in response to enhanced intervention in Malawi (Feng et al, 2010; Mathanga et al, 2005; World Health Organization, 2013a), others show no effect (Roca-Feltrer et al, 2012; Bennett et al, 2013; Okiro et al, 2013). Its potency against gametocytes could directly reduce malaria transmission in this setting, and lead to detectable changes in P. falciparum genetic structure
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