title: Delayed Plasmodium falciparum clearance following artesunate-mefloquine combination therapy in Thailand, 1997-2007.
abstract: BACKGROUND
  There is concern that artesunate resistance is developing in Southeast Asia. The purpose of this study is to investigate the prevalence of parasitaemia in the few days following treatment with artesunate-mefloquine (AM), which is an indirect measure of decreased artesunate susceptibility.
  
  
  METHODS
  This is a retrospective analysis of 31 therapeutic efficacy studies involving 1,327 patients treated with AM conducted by the Thai National Malaria Control Programme from 1997-2007.
  
  
  RESULTS
  The prevalence of patients with parasitaemia on day 2 was higher in the east compared to the west (east: 20%, west: 9%, OR 2.47, 95% CI: 1.77, 3.45). In addition, the prevalence of day-2 parasitaemia increased over time (OR for each year = 1.10, 95% CI: 1.03, 1.19). After controlling for initial parasitaemia and age, year and region remained important determinants of day-2 parasitaemia (OR for region = 3.98, 95%CI 2.63, 6.00; OR for year = 1.28, 95%CI: 1.17, 1.39). The presence of parasitaemia on day 2 and day 3 were specific, but not sensitive predictors of treatment failure.
  
  
  CONCLUSIONS
  Delayed resolution of parasitaemia after AM treatment increased in eastern Thailand between 1997 and 2007, which may be an early manifestation of decreased artesunate susceptibility. However, clinical and parasitological treatment failure after 28 days (which is related to both mefloquine and artesunate decreased susceptibility) is not changing over time. The presence of parasitaemia on day 2 is a poor indicator of AM 28-day treatment failure.
authors.affiliation: Bureau of Vector Borne Diseases, Department of Diseases Control, Ministry of Public Health, Nonthaburi, Thailand.
authors.forename: Saowanit
authors.initials: S
authors.lastname: Vijaykadga
authors.forename: Alisa P
authors.initials: AP
authors.lastname: Alker
authors.forename: Wichai
authors.initials: W
authors.lastname: Satimai
authors.forename: John R
authors.initials: JR
authors.lastname: MacArthur
authors.forename: Steven R
authors.initials: SR
authors.lastname: Meshnick
authors.forename: Chansuda
authors.initials: C
authors.lastname: Wongsrichanalai
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000962:Antimalarials / Q000008:administration & dosage*; D037621:Artemisinins / Q000008:administration & dosage*; D000077332:Artesunate; D002648:Child; D002675:Child, Preschool; D004351:Drug Resistance; D004359:Drug Therapy, Combination / Q000379:methods; D005260:Female; D006801:Humans; D016778:Malaria, Falciparum / Q000188:drug therapy* / Q000469:parasitology; D008297:Male; D015767:Mefloquine / Q000008:administration & dosage*; D008875:Middle Aged; D018512:Parasitemia / Q000188:drug therapy* / Q000469:parasitology; D010963:Plasmodium falciparum / Q000302:isolation & purification*; D012189:Retrospective Studies; D013785:Thailand; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000962:Antimalarials; D037621:Artemisinins; D000077332:Artesunate; D015767:Mefloquine