title: The return of chloroquine-susceptible Plasmodium falciparum malaria in Zambia.
abstract: BACKGROUND
  Plasmodium falciparum resistance to anti-malarial drugs remains a major obstacle to malaria control and elimination. The parasite has developed resistance to every anti-malarial drug introduced for wide-scale treatment. However, the spread of resistance may be reversible. Malawi was the first country to discontinue chloroquine use due to widespread resistance. Within a decade of the removal of drug pressure, the molecular marker of chloroquine-resistant malaria had disappeared and the drug was shown to have excellent clinical efficacy. Many countries have observed decreases in the prevalence of chloroquine resistance with the discontinuation of chloroquine use. In Zambia, chloroquine was used as first-line treatment for uncomplicated malaria until treatment failures led the Ministry of Health to replace it with artemether-lumefantrine in 2003. Specimens from a recent study were analysed to evaluate prevalence of chloroquine-resistant malaria in Nchelenge district a decade after chloroquine use was discontinued.
  
  
  METHODS
  Parasite DNA was extracted from dried blood spots collected by finger-prick in pregnant women who were enrolling in a clinical trial. The specimens underwent pyrosequencing to determine the genotype of the P. falciparum chloroquine resistance transporter, the gene that is associated with CQ resistance.
  
  
  RESULTS
  Three-hundred and two specimens were successfully analysed. No chloroquine-resistant genotypes were detected.
  
  
  CONCLUSIONS
  The study found the disappearance of chloroquine-resistant malaria after the removal of chloroquine drug pressure. Chloroquine may have a role for malaria prevention or treatment in Zambia and throughout the region in the future.
authors.affiliation: Tropical Diseases Research Centre (TDRC), 6th and 7th Floors, Ndola Central Hospital Building, P.O. Box 71769, Ndola, Zambia.
authors.forename: Sydney
authors.initials: S
authors.lastname: Mwanza
authors.affiliation: Division of Malaria Research, Institute for Global Health, University of Maryland School of Medicine, 685 West Baltimore Street, Baltimore, MD, 21201-1509, USA.
authors.forename: Sudhaunshu
authors.initials: S
authors.lastname: Joshi
authors.affiliation: Tropical Diseases Research Centre (TDRC), 6th and 7th Floors, Ndola Central Hospital Building, P.O. Box 71769, Ndola, Zambia.
authors.forename: Michael
authors.initials: M
authors.lastname: Nambozi
authors.affiliation: Tropical Diseases Research Centre (TDRC), 6th and 7th Floors, Ndola Central Hospital Building, P.O. Box 71769, Ndola, Zambia.
authors.forename: Justin
authors.initials: J
authors.lastname: Chileshe
authors.affiliation: Tropical Diseases Research Centre (TDRC), 6th and 7th Floors, Ndola Central Hospital Building, P.O. Box 71769, Ndola, Zambia.
authors.forename: Phidelis
authors.initials: P
authors.lastname: Malunga
authors.affiliation: Tropical Diseases Research Centre (TDRC), 6th and 7th Floors, Ndola Central Hospital Building, P.O. Box 71769, Ndola, Zambia.
authors.forename: Jean-Bertin Bukasa
authors.initials: JB
authors.lastname: Kabuya
authors.affiliation: Tropical Diseases Research Centre (TDRC), 6th and 7th Floors, Ndola Central Hospital Building, P.O. Box 71769, Ndola, Zambia.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Hachizovu
authors.affiliation: Tropical Diseases Research Centre (TDRC), 6th and 7th Floors, Ndola Central Hospital Building, P.O. Box 71769, Ndola, Zambia.
authors.forename: Christine
authors.initials: C
authors.lastname: Manyando
authors.affiliation: Tropical Diseases Research Centre (TDRC), 6th and 7th Floors, Ndola Central Hospital Building, P.O. Box 71769, Ndola, Zambia.
authors.forename: Modest
authors.initials: M
authors.lastname: Mulenga
authors.affiliation: Division of Malaria Research, Institute for Global Health, University of Maryland School of Medicine, 685 West Baltimore Street, Baltimore, MD, 21201-1509, USA. mlaufer@medicine.umaryland.edu.
authors.forename: Miriam
authors.identifier: http://orcid.org/0000-0001-8300-9593
authors.initials: M
authors.lastname: Laufer
mesh_terms: D000293:Adolescent; D000328:Adult; D000962:Antimalarials / Q000494:pharmacology*; D002738:Chloroquine / Q000494:pharmacology*; D003430:Cross-Sectional Studies; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D004351:Drug Resistance; D005260:Female; D005838:Genotype; D006801:Humans; D016778:Malaria, Falciparum / Q000453:epidemiology / Q000469:parasitology*; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000302:isolation & purification; D011247:Pregnancy; D015995:Prevalence; D017422:Sequence Analysis, DNA; D055815:Young Adult; D015024:Zambia / Q000453:epidemiology
chemical_list: D000962:Antimalarials; D016054:DNA, Protozoan; D002738:Chloroquine
keywords: Anti-malarial resistance; Chloroquine; Malaria; PfCRT; Plasmodium falciparum; Pyrosequencing; Zambia