Plasmodium vivax Chloroquine Resistance and Anemia in the Western Brazilian Amazon

Abstract

ABSTRACTData on chloroquine (CQ)-resistantPlasmodium vivaxin Latin America is limited, even with the current research efforts to sustain an efficient malaria control program in all these countries whereP. vivaxis endemic and where malaria still is a major public health issue. This study estimatedin vivoCQ resistance in patients with uncomplicatedP. vivaxmalaria, with use of CQ and primaquine simultaneously, in the Brazilian Amazon. Of a total of 135 enrolled subjects who accomplished the 28-day follow-up, parasitological failure was observed in 7 (5.2%) patients, in whom plasma CQ and desethylchloroquine (DCQ) concentrations were above 100 ng/dl. Univariate analysis showed that previous exposure to malaria and a higher initial mean parasitemia were associated with resistance but not with age or gender. In the multivariate analysis, only high initial parasitemia remained significant. Hemoglobin levels were similar at the beginning of the follow-up and were not associated with parasitemia. However, at day 3 and day 7, hemoglobin levels were significantly lower in patients presenting CQ resistance. TheP. vivaxdhfr(pvdhfr),pvmrp1,pvmdr1, andpvdhpsgene mutations were not related to resistance in this small sample.P. vivaxCQ resistance is already a problem in the Brazilian Amazon, which could be to some extent associated with the simultaneous report of anemia triggered by this parasite, a common complication of the disease in most of the areas of endemicity.