title: Sustained efficacy of artesunate-sulfadoxine-pyrimethamine against Plasmodium falciparum in Yemen and a renewed call for an adjunct single dose primaquine to clear gametocytes.
abstract: In Yemen, artesunate plus sulfadoxine-pyrimethamine (AS + SP) has been used as first-line treatment for uncomplicated falciparum malaria, which accounts for about 99 % of malaria cases. There is evidence that resistance to SP is increasing, with potential negative impact on efficacy, and in particular on curbing transmission. This study aims: (a) to evaluate the therapeutic efficacy of AS + SP treatment for uncomplicated falciparum malaria in Yemen; (b) to investigate the frequency of mutations in Plasmodium falciparum genes associated with resistance to AS (Kelch 13 propeller domain, pfK13) and SP (dihydrofolate reductase, pfdhfr, and dihydropteroate synthase, pfdhps); and (c) to assess the adequacy of this ACT to clear gametocytes.
  
  
  
  A 28-day in vivo evaluation of the clinical and parasitological response to three-day course of AS + SP was carried out in two areas of high endemicity (Hodeidah and Al-Mahwit provinces, Tehama region) in Yemen according to standard WHO protocol 2009. Clinical and parasitological indices were monitored over a 28-day follow-up, and the outcome was PCR-corrected. The frequencies of mutations in the pfdhfr, pfdhps, and pfK13 genes were obtained by sequencing following amplification.
  
  
  
  Eighty-six patients completed the study, with a cure rate of 96.5 % (94.2 % PCR-uncorrected). Whereas four (4.7 %) patients still showed parasitaemia on day 2 post-treatment, all were found negative for asexual malaria stages on days 3 and 7. The efficacy of gametocyte clearance was poor (14.5, 42.5 and 86.0 % on days 7, 14 and 28, respectively), with gametocytes persisting throughout the study in some patients. All the isolates sequenced had the pfk13 propeller domain wild-type allele, and mutations associated with SP failure were observed only for pfdhfr with the double mutation (S108N + N51I) found in 65.4 % of the isolates sequenced.
  
  
  
  In Yemen, AS + SP therapy remains effective for the treatment of uncomplicated falciparum malaria. Mutations were not detected in pfk13 or pfdhps, though double mutations were observed for pfdhfr. The observed persistent gametocytaemia re-enforces calls to add a single dose primaquine to this ACT in order to minimizes the potential for transmission and enhance regional efforts to eliminate malaria.
authors.affiliation: Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia.|Department of Microbiology and Parasitology, Faculty of Medicine and Health Sciences, University of Aden, Aden, Yemen.
authors.forename: Wahib M
authors.initials: WM
authors.lastname: Atroosh
authors.affiliation: Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia. halmekhlafi@yahoo.com.|Endemic and Tropical Diseases Unit, Medical Research Center, Jazan University, Jazan, Kingdom of Saudi Arabia. halmekhlafi@yahoo.com.|Department of Parasitology, Faculty of Medicine and Health Sciences, Sana'a University, Sana'a, Yemen. halmekhlafi@yahoo.com.
authors.forename: Hesham M
authors.initials: HM
authors.lastname: Al-Mekhlafi
authors.affiliation: UPMC Université Paris 06, Inserm (Institut National de la Santé et de la Recherche Medicale), Centre d'Immunologie et des Maladies Infectieuses (Cimi-Paris), UMR 1135, ERL CNRS 8255 (Centre National de la Recherche Scientifique), Sorbonne Universités, 91 Boulevard de l'Hôpital, F-75013, Paris, France. georges.snounou@upmc.fr.
authors.forename: Georges
authors.initials: G
authors.lastname: Snounou
authors.affiliation: National Malaria Control Programme, Ministry of Public Health and Population, Sana'a, Yemen.
authors.forename: Adel
authors.initials: A
authors.lastname: Al-Jasari
authors.affiliation: Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia.
authors.forename: Hany
authors.initials: H
authors.lastname: Sady
authors.affiliation: Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia.
authors.forename: Nabil A
authors.initials: NA
authors.lastname: Nasr
authors.affiliation: Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia.
authors.forename: Yee-Ling
authors.initials: YL
authors.lastname: Lau
authors.affiliation: Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia.|Centre for Research and Innovation, Taylor's University, 47500, Subang Jaya, Selangor, Malaysia.
authors.forename: Johari
authors.initials: J
authors.lastname: Surin
mesh_terms: D000293:Adolescent; D000328:Adult; D000962:Antimalarials / Q000494:pharmacology / Q000627:therapeutic use*; D037621:Artemisinins / Q000494:pharmacology / Q000627:therapeutic use*; D000077332:Artesunate; D002648:Child; D002675:Child, Preschool; D004338:Drug Combinations; D005260:Female; D005787:Gene Frequency; D006801:Humans; D007223:Infant; D016778:Malaria, Falciparum / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000235:genetics; D011319:Primaquine / Q000494:pharmacology / Q000627:therapeutic use*; D015800:Protozoan Proteins / Q000235:genetics; D011739:Pyrimethamine / Q000494:pharmacology / Q000627:therapeutic use*; D013413:Sulfadoxine / Q000494:pharmacology / Q000627:therapeutic use*; D016896:Treatment Outcome; D015006:Yemen; D055815:Young Adult
chemical_list: D000962:Antimalarials; D037621:Artemisinins; D004338:Drug Combinations; D015800:Protozoan Proteins; C001205:fanasil, pyrimethamine drug combination; D000077332:Artesunate; D013413:Sulfadoxine; D011319:Primaquine; D011739:Pyrimethamine
keywords: Artemisinin-based combination therapy; Drug resistance; Gametocytaemia; Kelch 13-propeller; Malaria; Plasmodium falciparum; Sulfadoxine-pyrimethamine; Yemen