Wilmer Marquiño

Efficacy of sulfadoxine-pyrimethamine and mefloquine for the treatment of uncomplicated Plasmodium falciparum malaria in the Amazon basin of Peru

In vivo antimalarial drug efficacy studies of uncomplicated Plasmodium falciparum malaria at an isolated site in the Amazon basin of Peru bordering Brazil and Colombia showed >50% RII/RIII resistance to sulfadoxine-pyrimethamine but no evidence of resistance to mefloquine.

Efficacy of mefloquine and mefloquine-artesunate for the treatment of uncomplicated Plasmodium falciparum malaria in the Amazon region of Bolivia.

We assessed the efficacy of mefloquine monotherapy and mefloquine–artesunate (MQ–AS) combination therapy for the treatment of Plasmodium falciparum malaria at four sites in the Bolivian Amazon region. Patients with uncomplicated P. falciparum infections between 5 and 60 years of age were randomly assigned to be treated with either MQ (15 mg/kg in a single oral dose) or MQ (15 mg/kg) plus AS (4 mg/kg daily for 3 days). A total of 143 patients were enrolled and followed for 28 days. None of the 73 patients who received MQ alone or the 70 patients who received MQ–AS combination therapy had recurrences of parasitaemia during the 28‐day follow‐up period. Asexual parasite densities fell significantly more rapidly and the proportion of patients with gametocytes was significantly lower on days 7–28 in patients treated with MQ–AS than in those treated with MQ alone. All patients tolerated the medications well. After this study, the Bolivian Ministry of Public Health changed its treatment policy for uncomplicated P. falciparum malaria in the Amazon region to combination therapy with MQ–AS to slow or prevent the development of resistance.

Efficacy and Effectiveness of Mefloquine and Artesunate Combination Therapy for Uncomplicated Plasmodium falciparum Malaria in the Peruvian Amazon

We evaluated the efficacy and effectiveness of mefloquine (MQ) plus artesunate (AS) to treat patients with uncomplicated malaria in the Peruvian Amazon Basin in April 2005-March 2006. Patients ≥ 1 year of age with fever (axillary temperature ≥ 37.5°C) or history of fever and Plasmodium falciparum monoinfection were included. Patients received antimalarial treatment with MQ (12.5 mg/kg/day for two days) and AS (4.0 mg/kg/day for three days) either by directly observed therapy or without directly observed therapy. After a 28-day follow-up, treatment efficacy and effectiveness were assessed on the basis of clinical and parasitologic outcomes. Ninety-six patients were enrolled in each study group; nine patients were lost to follow-up. All patients, except for one in the observed group, demonstrated adequate clinical and parasitologic response; none had detectable parasitemia on day 3. The efficacy of MQ + AS efficacy was 98.9% (95% confidence interval = 94.1-100.0%) and the effectiveness was 100.0% (95% confidence interval = 95.9-100.0%). Our study shows that MQ + AS is highly efficacious in the Peruvian Amazon.

Evaluation of a simple operational approach for monitoring resistance to antimalarial drugs in Peru.

Since 1994, the Peruvian Malaria Control Program has used a simplified operational approach for monitoring antimalarial drug efficacy, in which blood smears are taken 7 and 14 days after treatment from all patients diagnosed with malaria at Ministry of Health facilities. The proportion of patients with parasitaemia on one of their return visits provides an indication of the efficacy of the drug being administered. We compared this approach for antimalarial drug resistance monitoring to the more labour‐intensive and expensive World Health Organization (WHO) 14‐day in vivo efficacy trial at six sites in the Amazon Basin and the north coast of Peru. Although the proportion of treatment failures at 7 and 14 days identified by the operational monitoring system was considerably lower than the results of the WHO in vivo efficacy test, the operational approach did accurately reflect the overall efficacy or lack of efficacy of the drugs being evaluated. Differences in the results of the two methods were greatest in the Peruvian Amazon region, where fully supervised treatment and patient follow‐up is very difficult due to the widely dispersed population. While the operational approach cannot be considered an alternative to WHO in vivo testing for evaluating the efficacy of antimalarial drugs or for recommending changes in malaria treatment policy, if treatment is supervised and follow‐up blood smears taken as scheduled, this method could serve as a simple, inexpensive and sustainable early warning system for reduced drug efficacy.

Genetic polymorphism of Plasmodium falciparum isolates from Loreto, Peru

Eight genotypes of Plasmodium falciparum were detected after analysing blood samples obtained from 30 Peruvian jungle-dwelling patients in Loreto, a high transmission area for P. falciparum, using amplification of the polymorphic marker gene GLURP (glutamate-rich protein). Genotypes I (GLURP450) and VIII (GLURP800) were the most common (15/30 and 13/30, respectively). This single copy gene showed 15 patients to be infected with a single genotype of P. falciparum; the other 15 were infected with mixed genotypes, one of them with 4 genotypes. These findings are compatible with a high genetic complexity of P. falciparum. Further investigations are needed, using this and other markers, in order to design malaria control measures in Peru.