Plasmodium vivax malaria recurrence after radical treatment with chloroquine-primaquine standard regimen in Turbo, Colombia: Results from a prospective study.

Zuluaga-Idárraga L1, Blair S2, Akinyi Okoth S3, Udhayakumar V4, Marcet P5, Escalante AA6, Alexander N7, Rojas C8.

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Abstract

BACKGROUND:

Plasmodium vivax recurrences help maintain malaria transmission. They are caused by recrudescence, reinfection or relapse, which are not easily differentiated.

METHODS:

A longitudinal observational study took place in Turbo municipality, Colombia. Participants with uncomplicated P. vivax infection received supervised concomitantly treatment with chloroquine 25 mg/Kg and primaquine 0.25 mg/Kg/day for 14 days. Incidence of recurrence was assessed over 180 days. Samples were genotyped and origins of recurrences were established.

RESULTS:

134 participants were enrolled between February 2012 and July 2013, and 87 were followed for 180 days in which 29 recurrences were detected. Cumulative incidence of first recurrence was 24.1% (21/87) (CI 95% 14.6 to 33.7) and 86% (18/21) of them occurred between days 51 and 110. High genetic diversity of P. vivax was found and 12.5% (16/128) of the infections were polyclonal. Among detected recurrences 93.1% were genotyped as genetically identical to the one from the previous episode and 65.5% (19/29) were classified as relapses.

CONCLUSION:

Our results indicate that there is a high incidence of P. vivax malaria recurrence after treatment in Turbo municipality, Colombia, a large majority of which are likely relapses from the previous infection. We attribute this to the primaquine regimen currently used in Colombia, which may be insufficient to eliminate hypnozoites.