Artemisinin-based 42 PCR-corrected ACPR was 99.5% in the AL

Artemisinin-based combination therapy (ACT) remains
the first line treatment strategy globally. The current first line treatment
regime in Kenya is artemether-lumefantrine (AL), recognized as the first line
ACT and dihydroartemisinin-piperaquine (DP), the second line drug.ACT resistant
parasites have been reported in southeast (SE) Asia where parasites here have been
shown to be resistant to artemisinin, its derivatives and partner. So far, ACT
resistance has not been reported in Kenya but since ACTs have been in use for
the last decade, there is need to monitor for ACT resistance in parasites
circulating in Kenya using the genetic markers associated with ACT resistant
parasites in SE. This study therefore sets 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 and DP, in Msambweni constituency, Kwale County, on
the coast of Kenya in 2013.

Parasite DNA was extracted for molecular genotyping
on days 0-3, 7, 14, 21, 28 and 42.The parasite DNA was used to: 1) genotype msp2
and glurp genes to differentiate new
infections from recrudescent by gel electrophoresis and to calculate the
PCR-corrected adequate clinical parasitological response (ACPR) and 2) genotype
the drug resistance markers by PCR and capillary sequencing.  

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363 patients were enrolled in the trial; 201 (55%)
and 162 (45%) receivingAL and DP respectively. 49 participants were malaria
slide-positive after treatment; 1 (0.3%), 1 (0.3%), 8 (2.5%), 13 (4.1%) and 26
(9%) on days 7, 14, 21, 28 and 42 respectively.Overall, 89.5% (17/162) by DP
and 95.5% (9/201) by AL, of the participants had an unadjusted ACPR over the 42
day period. The msp2and glurp genotype analysis performed on
samplesfrom 39 of the 49 participants with confirmed parasite positive slide
infection after treatment revealed 8 (20%) recrudescent infections and 31 (79.5%)
re-infections.The day 42 PCR-corrected ACPR was 99.5% in the AL arm and 97.5%
in the DP arm.

The Pfcrt76T
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%). Onthe 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 also due to
the PCR-corrected ACPR recorded in both AL and DP. The high re-infection rate
suggests a need for continued malaria prevention interventions.