Changes in the treatment responses to artesunate-mefloquine on the northwestern border of Thailand during 13 years of continuous deployment.
BACKGROUND
Artemisinin combination treatments (ACT) are recommended as first line treatment for falciparum malaria throughout the malaria affected world. We reviewed the efficacy of a 3-day regimen of mefloquine and artesunate regimen (MAS(3)), over a 13 year period of continuous deployment as first-line treatment in camps for displaced persons and in clinics for migrant population along the Thai-Myanmar border.


RESULTS
3,264 patients were enrolled in prospective treatment trials between 1995 and 2007 and treated with MAS(3). The proportion of patients with parasitaemia persisting on day-2 increased significantly from 4.5% before 2001 to 21.9% since 2002 (p<0.001). Delayed parasite clearance was associated with increased risk of developing gametocytaemia (AOR = 2.29; 95% CI, 2.00-2.69, p = 0.002). Gametocytaemia on admission and carriage also increased over the years (p = 0.001, test for trend, for both). MAS(3) efficacy has declined slightly but significantly (Hazards ratio 1.13; 95% CI, 1.07-1.19, p<0.001), although efficacy in 2007 remained well within acceptable limits: 96.5% (95% CI, 91.0-98.7). The in vitro susceptibility of P. falciparum to artesunate increased significantly until 2002, but thereafter declined to levels close to those of 13 years ago (geometric mean in 2007: 4.2 nM/l; 95% CI, 3.2-5.5). The proportion of infections caused by parasites with increased pfmdr1 copy number rose from 30% (12/40) in 1996 to 53% (24/45) in 2006 (p = 0.012, test for trend).


CONCLUSIONS
Artesunate-mefloquine remains a highly efficacious antimalarial treatment in this area despite 13 years of widespread intense deployment, but there is evidence of a modest increase in resistance. Of particular concern is the slowing of parasitological response to artesunate and the associated increase in gametocyte carriage.
Carrara
Verena Ilona
VI
Shoklo Malaria Research Unit, Tak, Thailand.
Zwang
Julien
J
Ashley
Elizabeth A
EA
Price
Ric N
RN
Stepniewska
Kasia
K
Barends
Marion
M
Brockman
Alan
A
Anderson
Tim
T
McGready
Rose
R
Phaiphun
Lucy
L
Proux
Stephane
S
van Vugt
Michele
M
Hutagalung
Robert
R
Lwin
Khin Maung
KM
Phyo
Aung Pyae
AP
Preechapornkul
Piyanuch
P
Imwong
Mallika
M
Pukrittayakamee
Sasithon
S
Singhasivanon
Pratap
P
White
Nicholas J
NJ
Nosten
François
F
D000293:Adolescent; D000962:Antimalarials / Q000627:therapeutic use; D037621:Artemisinins / Q000627:therapeutic use*; D000077332:Artesunate; D002986:Clinical Trials as Topic; D004351:Drug Resistance; D005260:Female; D006801:Humans; D016778:Malaria, Falciparum / Q000188:drug therapy* / Q000453:epidemiology; D008297:Male; D015767:Mefloquine / Q000627:therapeutic use*; D012189:Retrospective Studies; D013785:Thailand; D016896:Treatment Outcome
D000962:Antimalarials; D037621:Artemisinins; D000077332:Artesunate; D015767:Mefloquine