title: [Alteration in resistance of Plasmodium falciparum to chloroquine after cessation of chloroquine medication for twelve years].
abstract: In view of the fact the resistance of Plasmodium falciparum to chloroquine occurred extensively in Hainan, a decision was made in 1979 that the use of chloroquine should be quit in the whole province. A longitudinal survey on chloroquine-sensitivity of P. falciparum was carried out during 1981-1991 to observe the variation in resistance of the parasite after the cessation of the chloroquine medication for every 2-3 years. A tendency of progressive decline of resistance was revealed. By using in vitro test, the rate of chloroquine-resistant P. falciparum dropped from 97.9% in 1981 to 60.9% in 1991 (P < 0.001). The mean dosage of chloroquine for complete inhibition of schizont formation declined from 10.46 pmol/microliters in 1981 to 3.02 pmol/microliters in 1991 (P < 0.001). The percentage of population requiring larger dosage (6.4 pmol/microliters to completely inhibit schizont formation declined from 83.3% in 1981 to 17.4% in 1991 (P < 0.001); whereas those requiring small dosage (1.6 pmol/microliters), increased from 4.2% in 1981 to 60.8% in 1991 (P < 0.001). In in vivo test, the rate of chloroquine-resistant P. falciparum decreased from 84.2% in 1981 to 40% in 1991 (P < 0.001). The proportion of RII plus RIII cases of the total resistant cases dropped from 59.4% in 1981 to 37.5% in 1991 (0.02 > P > 0.01).
authors.affiliation: Institute of Parasitic Diseases, Chinese Academy of Preventive Medicine Shanghai.
authors.forename: D Q
authors.initials: DQ
authors.lastname: Liu
authors.forename: R J
authors.initials: RJ
authors.lastname: Liu
authors.forename: D X
authors.initials: DX
authors.lastname: Ren
authors.forename: D Q
authors.initials: DQ
authors.lastname: Gao
authors.forename: C Y
authors.initials: CY
authors.lastname: Zhang
authors.forename: C P
authors.initials: CP
authors.lastname: Qiu
authors.forename: X Z
authors.initials: XZ
authors.lastname: Cai
authors.forename: C F
authors.initials: CF
authors.lastname: Ling
authors.forename: A H
authors.initials: AH
authors.lastname: Liang
authors.forename: Y
authors.initials: Y
authors.lastname: Tang
mesh_terms: D000818:Animals; D002738:Chloroquine / Q000494:pharmacology* / Q000627:therapeutic use; D004351:Drug Resistance; D066298:In Vitro Techniques; D008137:Longitudinal Studies; D016778:Malaria, Falciparum / Q000188:drug therapy / Q000469:parasitology; D010963:Plasmodium falciparum / Q000187:drug effects*; D013997:Time Factors
chemical_list: D002738:Chloroquine