Efficacy of artemisinin-based combination therapies for the treatment of falciparum malaria in Pakistan (2007-2015): In vivo response and dhfr and dhps mutations

Artesunate + sulfadoxine-pyrimethamine (AS + SP) and artemether+ lumefantrine (AL) are the first- and second line treatments, respectively, for the treatment of falciparum infections and dihydroartemsinin + piperaquine (DHA+PPQ) is a potential candidate in case AS + SP or AL fails in Pakistan. The therapeutic efficacies of AS+SP (5 sites in 2007, 2 sites in 2011 and 2 sites in 2012), AL (2 sites in 2012) and DHA+PPQ (2 sites in 2015) were evaluated in seven sentinel sites. Clinical and parasito-logical outcomes were evaluated among eligible patients. Mutations of the P. falciparum dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) genes were investigated. After PCR correction, a 98.5-100% adequate clinical and parasitological response (ACPR) for AS + SP and a 98.8-100% ACPR for AL were observed by day 28, as well as a 100% ACPR by day 42 for DHA + PPQ. The prevalences of mutants dhfr S108N (100%) and C59R (98%-100%) reached or were near fixation. The double dhfr (C59R/S108N) mutant was dominant (96%-100%) at all sites. The triple dhfr (N51I/C5912/S108N) mutant was rare (1.1%-2.3%). The prevalence of dhps A437G varied between 38% and 70%. A combination of triple dhfr/dhps (C5912/S108N+A437G or N51I/S108N+A437G) mutants was observed (38%-69%). A quadruple dhfr/dhps (N51I/C59R/S108N+A437G) mutation was very rare and no quintuple (N51I/C59R/S108N+A437G/K540E) mutations were detected. AS+ SP remains highly effective in Pakistan. However, molecular data indicate that SP resistance is being established, although mutations that confer a high risk of SP treatment failure are rare or non-existent. This underscores the need for close monitoring of both in vivo AS + SP efficacy and dhfr and dhps mutations to inform national treatment policy. (C) 2016 Published by Elsevier B.V.