title: Return of chloroquine-sensitive Plasmodium falciparum parasites and emergence of chloroquine-resistant Plasmodium vivax in Ethiopia.
abstract: BACKGROUND
  Increased resistance by Plasmodium falciparum parasites led to the withdrawal of the antimalarial drugs chloroquine and sulphadoxine-pyrimethamine in Ethiopia. Since 2004 artemether-lumefantrine has served to treat uncomplicated P. falciparum malaria. However, increasing reports on delayed parasite clearance to artemisinin opens up a new challenge in anti-malarial therapy. With the complete withdrawal of CQ for the treatment of Plasmodium falciparum malaria, this study assessed the evolution of CQ resistance by investigating the prevalence of mutant alleles in the pfmdr1 and pfcrt genes in P. falciparum and pvmdr1 gene in Plasmodium vivax in Southern and Eastern Ethiopia.
  
  
  METHODS
  Of the 1,416 febrile patients attending primary health facilities in Southern Ethiopia, 329 febrile patients positive for P. falciparum or P. vivax were recruited. Similarly of the 1,304 febrile patients from Eastern Ethiopia, 81 febrile patients positive for P. falciparum or P. vivax were included in the study. Of the 410 finger prick blood samples collected from malaria patients, we used direct sequencing to investigate the prevalence of mutations in pfcrt and pfmdr1. This included determining the gene copy number in pfmdr1 in 195 P. falciparum clinical isolates, and mutations in the pvmdr1 locus in 215 P. vivax clinical isolates.
  
  
  RESULTS
  The pfcrt K76 CQ-sensitive allele was observed in 84.1% of the investigated P.falciparum clinical isolates. The pfcrt double mutations (K76T and C72S) were observed less than 3%. The pfcrt SVMNT haplotype was also found to be present in clinical isolates from Ethiopia. The pfcrt CVMNK-sensitive haplotypes were frequently observed (95.9%). The pfmdr1 mutation N86Y was observed only in 14.9% compared to 85.1% of the clinical isolates that carried sensitive alleles. Also, the sensitive pfmdr1 Y184 allele was more common, in 94.9% of clinical isolates. None of the investigated P. falciparum clinical isolates carried S1034C, N1042D and D1246Y pfmdr1 polymorphisms. All investigated P. falciparum clinical isolates from Southern and Eastern Ethiopia carried only a single copy of the mutant pfmdr1 gene.
  
  
  CONCLUSIONS
  The study reports for the first time the return of chloroquine sensitive P. falciparum in Ethiopia. These findings support the rationale for the use of CQ-based combination drugs as a possible future alternative.
authors: Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa, Ethiopia. se.kebede@gmail.com.
authors: Seleshi Kebede
authors: SK
authors: Mekonnen
authors: Abraham
authors: A
authors: Aseffa
authors: Nega
authors: N
authors: Berhe
authors: Tilahun
authors: T
authors: Teklehaymanot
authors: Ronald M
authors: RM
authors: Clouse
authors: Tamirat
authors: T
authors: Gebru
authors: Girmay
authors: G
authors: Medhin
authors: Thirumalaisamy P
authors: TP
authors: Velavan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000962:Antimalarials / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D002738:Chloroquine / Q000494:pharmacology*; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D004351:Drug Resistance; D005002:Ethiopia / Q000453:epidemiology; D005260:Female; D006801:Humans; D007223:Infant; D008288:Malaria / Q000453:epidemiology / Q000469:parasitology; D008297:Male; D026901:Membrane Transport Proteins / Q000235:genetics; D008875:Middle Aged; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D010966:Plasmodium vivax / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D015995:Prevalence; D015800:Protozoan Proteins / Q000235:genetics; D017422:Sequence Analysis, DNA; D055815:Young Adult
chemical_list: D000962:Antimalarials; D002738:Chloroquine; D016054:DNA, Protozoan; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D015800:Protozoan Proteins; C513498:Mdr1 protein, Plasmodium falciparum; C541684:Mdr1 protein, Plasmodium vivax; C416369:PfCRT protein, Plasmodium falciparum