Molecular Analysis of Antimalarial Resistance Markers in Parasite Samples Obtained From Children Recruited Into a Drug Efficacy Trial in Kwale, Kenya, 2013.

Abstract

Artemisinin-based combination therapies (ACTs) have resulted to a significant drop in malaria incidences by 18% from 2010 to 2016. Unfortunately, ACT resistance reported in Western Cambodia in 2008 poses a consequential threat to the efficacy of artemisinin (ART). Furthermore, ART-resistance has sprouted in several countries in Southeast (SE) Asia. Thus far, ACT resistance has not been reported in Kenya but the main concern is the possible spread of resistant parasites from SE Asia to Sub-Saharan Africa. This study therefore set out to distinguish recrudescent from new infections and analyze known drug resistance markers, k13, Pfcrt and Pfmdr1 in pre- and post-treatment dried blood spot (DBS) samples, obtained from children, recruited into an antimalarial drug efficacy trial of AL (Artemether-lumefantrine) and DP (dihydroartemisinin-piperaquine), in Msambweni constituency, Kwale County, on the coast of Kenya in 2013. Parasite DNA was extracted for molecular genotyping on days 0, 1, 2, 3, 7, 14, 21, 28 and 42. The parasite DNA was used to: 1) genotype glurp and msp2 genes to differentiate re- from recrudescent-infections by gel electrophoresis and to calculate the PCRcorrected adequate clinical parasitological response (ACPR) and 2) genotype the drug resistance markers by PCR and capillary sequencing. In total, 363 children were recruited into the trial; 162 (45%) and 201 (55%) receiving AL and DP respectively. 49 participants were malaria slide-positive after treatment; 1, 1, 8, 13 and 26 on days 7, 14, 21, 28 and 42, respectively. The msp2 and glurp genotype analysis performed on samples from 39 of the 49 participants. This revealed 8 (20.5%) recrudescent infections and 31 (79.5%) re-infections. The day 42 PCR-corrected ACPR was 97.5% and 99.5% in the AL and DP arm respectively. The Pfcrt 76T mutation was seen to decrease from 27% (day 0) to 9.7% (day 42) as part of the CVIET haplotype. For Pfmdr1, there was a slight increase in the 86Y mutant frequency from 11% (day 0) to 12% (day 1), however, the mutant allele was cleared in all the subsequent days. The prevalence of the 184F mutation remained stable at 41% (day 0, n=208), 56% (day 1, n=116) and 40% (days 2 to 42, n=20) and the mutant 1246Y allele was observed only on day 0 (7%). In the k13 propeller domain only one synonymous mutation was observed on day 42 at codon 487 from a GTA -> GTG encoding the amino acid Valine. Our results suggest that ACTs were still effective at the study site in 2013, since no k13 mutations were observed and due to the high PCR-corrected ACPR recorded in both AL and DP. The high re-infection rate suggests a need for continued drug resistance surveillance.