title: Plasmodium vivax malaria relapses at a travel medicine centre in Rio de Janeiro, a non-endemic area in Brazil.
abstract: BACKGROUND
  Malaria is a potentially severe disease widely distributed in tropical and subtropical regions worldwide. Clinically, the progression of the disease can be life-threatening if it is not promptly diagnosed and properly treated. Through treatment, the radical cure of Plasmodium vivax infection can be achieved, thus preventing potential relapses and the emergence of new cases outside the Amazon region in Brazil. Surveillance for therapeutic failure in non-endemic areas is advantageous, as it is unlikely that recurrence of the disease can be attributed to a new malaria infection in these regions.
  
  
  METHODS
  An observational study of 53 cases of P. vivax and mixed (P. vivax and Plasmodium falciparum) malaria was conducted at a travel medicine centre between 2005 and 2011 in Rio de Janeiro and a descriptive analysis of the potential factors related to recurrence of P. vivax malaria was performed. Groups with different therapeutic responses were compared using survival analysis based on the length of time to recurrence and a set of independent variables thought to be associated with recurrence.
  
  
  RESULTS
  Twenty-one relapses (39.6%) of P. vivax malaria were observed. The overall median time to relapse, obtained by the Kaplan-Meier method, was 108 days, and the survival analysis demonstrated an association between non-weight-adjusted primaquine dosing and the occurrence of relapse (p < 0.03). Primaquine total dose at 3.6 mg/kg gave improved results in preventing relapses.
  
  
  CONCLUSIONS
  A known challenge to individual cure and environmental control of malaria is the possibility of an inappropriate, non-weight-based primaquine dosing, which should be considered a potential cause of P. vivax malaria relapse. Indeed, the total dose of primaquine associated with non-occurrence of relapses was higher than recommended by Brazilian guidelines.
authors: Instituto de Pesquisa Clínica Evandro Chagas (IPEC), Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro, Av, Brasil 4365, Manguinhos, Rio de Janeiro, RJ - CEP 21,045-900, RJ -, Brazil.
authors: Renata S
authors: RS
authors: Pedro
authors: Lusiele
authors: L
authors: Guaraldo
authors: Dayse P
authors: DP
authors: Campos
authors: Anielle P
authors: AP
authors: Costa
authors: Cláudio T
authors: CT
authors: Daniel-Ribeiro
authors: Patrícia
authors: P
authors: Brasil
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D000962:Antimalarials / Q000008:administration & dosage*; D001938:Brazil / Q000453:epidemiology; D005260:Female; D006801:Humans; D016780:Malaria, Vivax / Q000188:drug therapy / Q000453:epidemiology* / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D011319:Primaquine / Q000008:administration & dosage*; D012008:Recurrence; D012307:Risk Factors; D017211:Treatment Failure; D055815:Young Adult
chemical_list: D000962:Antimalarials; D011319:Primaquine