title: Resistance of Plasmodium falciparum to antimalarial drugs in a highly endemic area of southern Viet Nam: a study in vivo and in vitro.
abstract: To assess the antimalarial sensitivity of Plasmodium falciparum in vivo and in vitro in a highly endemic area of southern Viet Nam, a field study was conducted (in 1999) at a rubber plantation in Binh Phuoc Province north of Ho Chi Minh City. Fifty patients were treated with either artesunate (4 mg/kg on day 0, then 2 mg/kg on day 1 to 4) or mefloquine (10 mg/kg at 0 h, then 5 mg/kg at 6 h), and their progress was followed for 28 days under standard WHO protocols. Blood spots were taken at baseline from all patients, as well as from those who redeveloped parasitaemia during follow-up, for polymerase chain reaction (PCR) determination of parasite genotypes to assist differentiation of re-infection from recrudescence. Both treatments cleared parasites within 5 days. Of the 25 mefloquine-treated patients, 2 (8%) re-presented with probable re-infections. For artesunate, 4 patients (16%) had re-infections and 5 (20%) had recrudescences. Sensitivity tests in vitro of pre-treatment P. falciparum isolates showed geometric mean IC50 values of 29, 38, 209 and 15 nmol/L for chloroquine (n = 32), mefloquine (n = 33), quinine (n = 31) and artemisinin (n = 31), respectively. There were significant correlations between IC50s for artemisinin and mefloquine (r = 0.72, P = 0.004), and chloroquine and quinine (r = 0.44, P = 0.05). These data show that, although mefloquine has been used for 10 years in Binh Phuoc Province, it remains fully effective, perhaps because an artemisinin derivative is commonly given at the same time. The recrudescence rate for artesunate is similar to those reported in other epidemiological contexts. The present in-vitro data imply that quinine remains effective and that reduced drug pressure has been associated with increased sensitivity of local strains of P. falciparum to chloroquine. Although from one hyperendemic area, these results may have implications for antimalarial prophylaxis and treatment strategies for residents and travellers to southern Viet Nam.
authors.affiliation: National Institute of Malariology, Parasitology and Entomology, Luong, Vinh Road, Hanoi, Viet Nam.
authors.forename: N M
authors.initials: NM
authors.lastname: Huong
authors.forename: S
authors.initials: S
authors.lastname: Hewitt
authors.forename: T M
authors.initials: TM
authors.lastname: Davis
authors.forename: L D
authors.initials: LD
authors.lastname: Dao
authors.forename: T Q
authors.initials: TQ
authors.lastname: Toan
authors.forename: T B
authors.initials: TB
authors.lastname: Kim
authors.forename: N T
authors.initials: NT
authors.lastname: Hanh
authors.forename: V N
authors.initials: VN
authors.lastname: Phuong
authors.forename: D H
authors.initials: DH
authors.lastname: Nhan
authors.forename: L D
authors.initials: LD
authors.lastname: Cong
mesh_terms: D000328:Adult; D000962:Antimalarials / Q000627:therapeutic use*; D037621:Artemisinins; D000077332:Artesunate; D004351:Drug Resistance; D019353:Endemic Diseases; D005260:Female; D006801:Humans; D016778:Malaria, Falciparum / Q000188:drug therapy*; D008297:Male; D015767:Mefloquine / Q000627:therapeutic use*; D008826:Microbial Sensitivity Tests; D012717:Sesquiterpenes / Q000627:therapeutic use*; D014744:Vietnam
chemical_list: D000962:Antimalarials; D037621:Artemisinins; D012717:Sesquiterpenes; D000077332:Artesunate; D015767:Mefloquine