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The online version of this article (doi:10.1186/1475-2875-11-245) contains supplementary material, which is available to authorized users.
The authors have no conflicts of interest to disclose.
RSP: responsible for conception and design of the work, data collection, data analysis, data interpretation and drafting the manuscript. PB: responsible for conception and design of the work, data analysis, data interpretation, literature review and reviewing the manuscript. LG: responsible for conception and design of the work, data analysis, data interpretation, literature review and reviewing the manuscript. DC: responsible for data analysis and interpretation. APC: responsible for data collection and helped to review the text. CTDR: helped in the design of the work and reviewed the text up to the final version to be published. All authors read and approved the final manuscript.
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.
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.
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.
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.