Treatment Of Acute Uncomplicated Malaria Research Articles

Design, Implementation, and Coordination of Malaria Therapeutic Efficacy Studies in Nigeria in 2018.

Prior to 2018, malaria therapeutic efficacy studies (TESs) in Nigeria were implemented separately at different sites, as assigned by the National Malaria Elimination Program (NMEP). In 2018, however, the NMEP engaged the Nigerian Institute of Medical Research to coordinate the 2018 TESs in 3 of 14 sentinel sites with the objective of standardizing their conduct across all three sites: Enugu, Kano, and Plateau states in three of six geopolitical zones. Artemether-lumefantrine and artesunate-amodiaquine, the two first-line drugs for treatment of acute uncomplicated malaria in Nigeria, were tested in both Kano and Plateau states. In Enugu State, however, artemether-lumefantrine and dihydroartemisinin-piperaquine were the test drugs, with dihydroartemisinin-piperaquine being tested for potential inclusion in Nigerian treatment policy. The TES was conducted in 6-month to 8-year-old children and was funded by the Global Fund with additional support from the WHO. A multipartite core team comprised of the NMEP, the WHO, the U.S. Presidential Malaria Initiative, academia, and the Nigerian Institute of Medical Research was set up to oversee the execution of the 2018 TES. This communication reports best practices adopted to guide its coordination, and lessons learned during in the process, including applying developed standard operating procedures, powering the sample size adequately for each site to report independently, training the investigating team for fieldwork, facilitating stratification of decisions, determining efficiencies derived from monitoring and quality assessment, and optimizing logistics. The planning and coordination of the 2018 TES activities is a model of a consultative process for the sustainability of antimalarial resistance surveillance in Nigeria.

Efficacy and safety of pyronaridine–artesunate versus artemether–lumefantrine in the treatment of acute uncomplicated malaria in children in South-West Nigeria: an open-labelled randomized controlled trial

BackgroundIn Nigeria, declining responsiveness to artemether–lumefantrine (AL), the artemisinin-based combination therapy (ACT) of choice since 2005, has been reported. Pyronaridine–artesunate (PA) is a newer fixed-dose ACT recently prequalified by the WHO for the treatment of uncomplicated falciparum malaria. However, PA data from the Nigerian pediatric population is scarce. Therefore, the efficacy and safety of PA and AL using the WHO 28-day anti-malarial therapeutic efficacy study protocol in Ibadan, southwest Nigeria, were compared.MethodsIn an open-labelled, randomized, controlled clinical trial, 172 children aged 3–144 months with a history of fever and microscopically confirmed uncomplicated Plasmodium falciparum malaria were enrolled in southwest Nigeria. Enrollees were randomly assigned to receive PA or AL at standard dosages according to body weight for 3 days. Venous blood was obtained for hematology, blood chemistry, and liver function tests on days 0, 3, 7, and 28 as part of the safety evaluation.Results165 (95.9%) of the enrolled individuals completed the study. About half (52.3%; 90/172) of enrollees were male. Eighty-seven (50.6%) received AL, while 85 (49.4%) received PA. Day 28, adequate clinical and parasitological response for PA was 92.7% [(76/82) 95% CI 83.1, 95.9] and 71.1% [(59/83) 95% CI 60.4, 79.9] for AL (0.001). Fever and parasite clearance were similar in both groups. Two of six and eight of 24 parasite recurrences were observed among PA- and AL-treated children, respectively. PCR-corrected Day-28 cure rates for PA were 97.4% (76/78) and 88.1% (59/67) for AL (= 0.04) in the per-protocol population after new infections were censored. Hematological recovery at day 28 was significantly better among PA-treated patients (34.9% 2.8) compared to those treated with AL (33.1% 3.0) (0.002). Adverse events in both treatment arms were mild and similar to the symptoms of malaria infection. Blood chemistry and liver function tests were mostly within normal limits, with an occasional marginal rise.ConclusionPA and AL were well-tolerated. PA was significantly more efficacious than AL in both the PCR-uncorrected and PCR-corrected per-protocol populations during this study. The results of this study support the inclusion of PA in the anti-malarial treatment guidelines in Nigeria.Retrospective trial registrationClinicaltrials.gov: NCT05192265.

Pyronaridine–artesunate real-world safety, tolerability, and effectiveness in malaria patients in 5 African countries: A single-arm, open-label, cohort event monitoring study

BackgroundIn Phase II/III randomized controlled clinical trials for the treatment of acute uncomplicated malaria, pyronaridine–artesunate demonstrated high efficacy and a safety profile consistent with that of comparators, except that asymptomatic, mainly mild-to-moderate transient increases in liver aminotransferases were reported for some patients. Hepatic safety, tolerability, and effectiveness have not been previously assessed under real-world conditions in Africa.Methods and findingsThis single-arm, open-label, cohort event monitoring study was conducted at 6 health centers in Cameroon, Democratic Republic of Congo, Gabon, Ivory Coast, and Republic of Congo between June 2017 and April 2019. The trial protocol as closely as possible resembled real-world clinical practice for the treatment of malaria at the centers. Eligible patients were adults or children of either sex, weighing at least 5 kg, with acute uncomplicated malaria who did not have contraindications for pyronaridine–artesunate treatment as per the summary of product characteristics. Patients received fixed-dose pyronaridine–artesunate once daily for 3 days, dosed by body weight, without regard to food intake. A tablet formulation was used in adults and adolescents and a pediatric granule formulation in children and infants under 20 kg body weight. The primary outcome was the hepatic event incidence, defined as the appearance of the clinical signs and symptoms of hepatotoxicity confirmed by a >2× rise in alanine aminotransferase/aspartate aminotransferase (ALT/AST) versus baseline in patients with baseline ALT/AST >2× the upper limit of normal (ULN). As a secondary outcome, this was assessed in patients with ALT/AST >2× ULN prior to treatment versus a matched cohort of patients with normal baseline ALT/AST. The safety population comprised 7,154 patients, of mean age 13.9 years (standard deviation (SD) 14.6), around half of whom were male (3,569 [49.9%]). Patients experienced 8,560 malaria episodes; 158 occurred in patients with baseline ALT/AST elevations >2×ULN. No protocol-defined hepatic events occurred following pyronaridine–artesunate treatment of malaria patients with or without baseline hepatic dysfunction. Thus, no cohort comparison could be undertaken. Also, as postbaseline clinical chemistry was only performed where clinically indicated, postbaseline ALT/AST levels were not systematically assessed for all patients. Adverse events of any cause occurred in 20.8% (1,490/7,154) of patients, most frequently pyrexia (5.1% [366/7,154]) and vomiting (4.2% [303/7,154]). Adjusting for Plasmodium falciparum reinfection, clinical effectiveness at day 28 was 98.6% ([7,369/7,746] 95% confidence interval (CI) 98.3 to 98.9) in the per-protocol population. There was no indication that comorbidities or malnutrition adversely affected outcomes. The key study limitation was that postbaseline clinical biochemistry was only evaluated when clinically indicated.ConclusionsPyronaridine–artesunate had good tolerability and effectiveness in a representative African population under conditions similar to everyday clinical practice. These findings support pyronaridine–artesunate as an operationally useful addition to the management of acute uncomplicated malaria.Trial registrationClinicalTrials.gov NCT03201770.

Evaluation of the Comparative Efficacy and Safety of Artemether-Lumefantrine, Artesunate-Amodiaquine and Artesunate-Amodiaquine-Chlorpheniramine (Artemoclo™) for the Treatment of Acute Uncomplicated Malaria in Nigerian Children

Objective: To evaluate the comparative efficacy and safety of artemether-lumefantrine (AL), artesunate-amodiaquine (ASAQ) and artesunate-amodiaquine-chlorpheniramine (AQC) for the treatment of acute uncomplicated malaria among Southwest Nigerian children. Subjects and Methods: One hundred and sixty children aged 6 months to 14 years with acute uncomplicated malaria were randomized to AL (n = 53), ASAQ (n = 53), or AQC (n = 54). Enrollees were seen daily on days 0-3 and then on days 7, 14, 21, 28 and 42 for clinical and parasitological evaluations. Paired samples of genomic DNA at enrolment and at the time of recurrent parasitaemia were genotyped using nested PCR to distinguish between reinfection and recrudescence. Detailed haematological and biochemical evaluations were carried out in a subset of enrollees on days 0, 7 and 28 as part of a safety evaluation. Results: Of the 160 children, 144 (90%) completed the study. The mean fever clearance times and parasite clearance times for AL, ASAQ and AQC were comparable (p = 0.94 and p = 0.122, respectively). On day 14, the adequate clinical and parasitological response (ACPR) for AL and AQC was 100% and for ASAQ it was 90% (p = 0.39). The PCR-uncorrected results on days 28 and 42 and the ACPR-corrected results on day 42 were similar for all drugs (p = 0.62 and p = 0.56, respectively). AQC resulted in the best parasite clearance and haematological recovery on day 2 (p = 0.022 and p = 0.018, respectively). Biochemical parameters were not adversely affected by the three artemisinin-based combination therapies (ACTs) and these were well tolerated. Conclusion: The three ACTs were efficacious and safe, but AQC resulted in a better haematological recovery on day 2 and higher cure rates throughout the study period.

Different Patterns of pfcrt and pfmdr1 Polymorphisms in P. falciparum Isolates from Nigeria and Brazil: The Potential Role of Antimalarial Drug Selection Pressure

The effect of antimalarial drug selection on pfcrt and pfmdr1 polymorphisms in Plasmodium falciparum isolates from two distinct geographical locations was determined in 70 and 18 P. falciparum isolates from Nigeria and Brazil, respectively, using nested polymerase chain reaction and direct DNA sequencing approaches. All isolates from Brazil and 72% from Nigeria harbored the mutant SVMNT and CVIET pfcrt haplotype, respectively. The pfcrt CVMNT haplotype was also observed in (7%) of the Nigerian samples. One hundred percent (100%) and 54% of the parasites from Brazil and Nigeria, respectively, harbored wild-type pfmdr1Asn86. We provide first evidence of emergence of the CVMNT haplotype in West Africa. The high prevalence of pfcrt CVIET and SVMNT haplotypes in Nigeria and Brazil, respectively, is indicative of different selective pressure by chloroquine and amodiaquine. Continuous monitoring of pfcrt SVMNT haplotype is required in endemic areas of Africa, where artesunate-amodiaquine combination is used for treatment of acute uncomplicated malaria.

Clinical efficacy of a tea-bag formulation of <i>Cryptolepis sanguinolenta</i> root in the treatment of acute uncomplicated falciparum malaria

To evaluate the clinical efficacy and safety of a tea bag formulation of the root of C. sanguinolenta This is a prospective descriptive open trial. Patients were recruited from Korle-Bu, Mamprobi and Dansoman Polyclinics. Forty-four subjects with uncomplicated malaria were recruited for the study. Patients presented with clinical symptoms of malaria. Laboratory investigations conducted included malaria parasite counts, haematological indices and biochemical tests which were obtained before, during and after a 5-day treatment period, up to Day 28 posttreatment. All patients in the study were symptomatic with significant parasitaemia. Patients were given one teabag three times a day, that is, morning, noon and night, for five days of treatment. Fifty percent of the patients were cleared of their P. falciparum parasitaemia by 72 hours, and all by Day 7. Presenting symptoms of fever, chills, nausea and vomiting cleared rapidly, all by Day 3, but resolution of haematological and biochemical abnormalities associated with malaria was generally slow, a feature seen in malaria post-treatment. The overall cure rate was 93.5% due to two cases of recrudescence on Days 21 and 28. The laboratory findings did not suggest any toxicity. On the basis of fever clearance and disappearance of parasitaemia by Day 7, the formulation has been shown to be non-toxic and highly effective in the treatment of acute uncomplicated malaria.

The neurological assessment in young children treated with artesunate monotherapy or artesunate-mefloquine combination therapy for uncomplicated Plasmodium falciparum malaria

BackgroundMefloquine and artesunate combination therapy is the recommended first-line treatment for uncomplicated malaria throughout much of south-east Asia. Concerns have been raised about the potential central nervous system (CNS) effects of both drug components and there are no detailed reports in very young children.MethodsChildren, aged between three months and five years, with acute uncomplicated Plasmodium falciparum malaria were randomized to either 7 days of artesunate monotherapy or the same schedule of artesunate plus mefloquine on day 7 and 8. Neurological testing targeting coordination and behaviour was carried out at day 0, 7, 9, 10, 14 and 28. Non-febrile healthy control children from the same population were tested on days 0, 7, 14 and 28.ResultsFrom December 1994 to July 1997, 91 children with uncomplicated P. falciparum, 45 treated with artesunate monotherapy, 46 treated with mefloquine and artesunate combination therapy and 36 non-febrile controls, underwent neurological testing. Malaria and fever had a significant negative impact on testing performance. By contrast, the anti-malarial treatments were not associated with worsening performances in the various components of the test. Artesunate and mefloquine do not appear to have a significant influence on coordination and behaviour. Children treated with mefloquine were significantly less likely to suffer recurrent malaria infection during follow-up compared to those treated with artesunate alone (P = 0.033).ConclusionIn keeping with the results of randomized controlled trials in adults, mefloquine was not associated with a decrease in specific items of neurological performance. Likewise, children treated with artesunate did not perform significantly differently to control children. This study does not exclude subtle or rare treatment CNS effects of artesunate or mefloquine. Treatment of acute uncomplicated malaria results in a significant improvement on items of neurological performance.

Evaluation of the efficacy and safety of artemether-lumefantrine in the treatment of acute uncomplicated Plasmodium falciparum malaria in Nigerian infants and children

BackgroundThe six-dose regimen of artemether-lumefantrine (AL) is now considered the gold standard for the treatment of uncomplicated Plasmodium falciparum malaria. There are few reports evaluating co-artemether in very young Nigerian infants and children. Results of the evaluation of the six-dose regimen in very young infants and children in Nigeria are presented in this report.MethodsAs part of a larger African study, this open label, non-comparative trial, assessed the efficacy and safety of six-dose regimen of AL tablets in 103 Nigerian infants and children weighing between five and 25 kg suffering from acute uncomplicated malaria. Treatment was administered under supervision over three days with children as in-patients. 12-lead ECG tracings were taken pre-treatment and at day 3.ResultsNinety-three infants and children completed the study as stipulated by the protocol. Mean fever and parasite clearance times for the intent to treat population (ITT) were 24.9 h ± (1.28) and 26 h ± (4.14) and the corresponding figures for the per-protocol population (PP) were 19.24 h ± 13.9 and 25.62 h ± 11.25 respectively. Day 14 cure rates for the ITT and PP were 95.1% and 100% respectively while day 28 cure rates were 91.3% and 95.7% respectively. The overall PCR corrected day 28 cure rate was 95.1% for the ITT. The six-dose regimen of AL was well tolerated with no drug-related serious adverse events. Although six patients recorded a QTc prolongation of > 60 ms on D3 over D0 recording, no patient recorded a QTc interval > 500 ms.ConclusionThe six-dose regimen of AL tablets is safe and effective for the treatment of acute uncomplicated malaria in Nigerian infants and children weighing between five and 25 kg.Trial registrationNCT00709969

High efficacy of two artemisinin‐based combinations (artemether–lumefantrine and artesunate plus amodiaquine) for acute uncomplicated malaria in Ibadan, Nigeria

To test the hypothesis that artesunate plus amodiaquine (ASAQ) is as effective as artemether-lumefantrine (AL) in the treatment of acute uncomplicated malaria in Nigerian children. In an open label, randomized controlled clinical trial, children aged 6 months to 10 years were randomized to receive artesunate (4 mg/kg daily) plus amodiaquine (10 mg/kg daily) or AL (5-14 kg, one tablet; 15-24 kg, two tablets and 25-34 kg, three tablets twice daily). Both drug regimens were given for 3 days and follow-up was for 28 days. A total of 132 children (66 in each group) were randomized to receive either ASAQ or AL. Day 28 cure rates in the per protocol (PP) population were 93% for ASAQ and 95% for AL (OR = 0.71, 95% CI = 0.12-3.99, rho = 0.66). Using Kaplan-Meier product-limit estimates of failure, the median survival time for ASAQ was 21 days and for AL 28 days (P = 0.294). PCR corrected day 28 cure rate for PP populations were 98.4% for ASAQ and 100% for AL. Both drugs were well-tolerated. ASAQ is as effective as AL and both combinations were efficacious and safe.

Chloroquine resistant Plasmodium falciparum malaria in Osogbo Nigeria: efficacy of amodiaquine + sulfadoxine-pyrimethamine and chloroquine + chlorpheniramine for treatment

Chloroquine (CQ) resistance in Plasmodium falciparum contributes to increasing malaria-attributable morbidity and mortality in Sub-Saharan Africa. Despite a change in drug policy, continued prescription of CQ did not abate. Therefore the therapeutic efficacy of CQ in uncomplicated falciparum malaria patients was assessed in a standard 28-day protocol in 116 children aged between six and 120 months in Osogbo, Southwest Nigeria. Parasitological and clinical assessments of response to treatment showed that 72 (62.1%) of the patients were cured and 44 (37.9%) failed the CQ treatment. High initial parasite density and young age were independent predictors for early treatment failure. Out of the 44 patients that failed CQ, 24 received amodiaquine + sulphadoxine/pyrimethamine (AQ+SP) and 20 received chlorpheniramine + chloroquine (CH+CQ) combinations. Mean fever clearance time in those treated with AQ+SP was not significantly different from those treated with CH+CQ (p = 0.05). There was no significant difference in the mean parasite density of the two groups. The cure rate for AQ+SP group was 92% while those of CH+CQ was 85%. There was a significant difference in parasite clearance time (p = 0.01) between the two groups. The 38% treatment failure for CQ reported in this study is higher than the 10% recommended by World Health Organization in other to effect change in antimalarial treatment policy. Hence we conclude that CQ can no more be solely relied upon for the treatment of falciparum malaria in Osogbo, Nigeria. AQ+SP and CH+CQ are effective in the treatment of acute uncomplicated malaria and may be considered as useful alternative drugs in the absence of artemisinin-based combination therapies.

Enhanced Efficacy of Amodiaquine and Chlorpheniramine Combination over Amodiaquine Alone in the Treatment of Acute Uncomplicated Plasmodium falciparum Malaria in Children

Objective: To evaluate the comparative efficacy of amodiaquine (AMQ) alone and the combination of AMQ and chlorpheniramine (CP) in the treatment of acute uncomplicated malaria in children. Subjects: Of the 110 children enrolled in the study, 103 with acute uncomplicated malaria, aged 6 months to 12 years, were evaluated using the 14-day modification of the WHO field test. The patients were randomized to 2 groups. Group 1 received supervised treatment with AMQ alone (10 mg AMQ base/kg daily for 3 days), while group 2 received supervised treatment with AMQ (same dose as group 1) plus CP (AMQCP) for 7 days. Results: Both treatment regimens were well tolerated and no patient was withdrawn as a result of recurrent vomiting or drug-related adverse events. There was no significant difference in mean fever and parasite clearance times. The cure rates at day 7 were 90.2 versus 100% (ρ = 0.027) for AMQ versus AMQCP, while the day 14 cure rates were 85.9 versus 98.1% for AMQ versus AMQCP, respectively (ρ = 0.016). Conclusion: The combination of AMQ plus CP proved significantly more effective than AMQ alone in the treatment of acute uncomplicated falciparum malaria, most probably due to the enhancement of the antimalarial effect of AMQ by CP. The combination of AMQCP could be a better alternative to AMQ alone as a companion drug in artemisinin-based combination therapies.

Efficacy and acceptability of oral artemether (Artemos<sup>TM</sup>) for the treatment of acute uncomplicated malaria in Ghana

Efficacy and acceptability of oral artemether (Artemos<sup>TM</sup>) for the treatment of acute uncomplicated malaria in Ghana

Traitement de l'accès palustre non compliqué de l'enfant en France en 2002

Context and objectives. – Imported P. falciparum malaria cases are rising in France reaching 1300 estimated children in 2000. Three years after the publication of therapeutic guidelines, the Groupe de Pédiatrie Tropicale conducted an observational survey in order to describe the practice of acute uncomplicated malaria treatments in children, to identify their limits and to make proposals to improve them. Methods. – A self administrated questionnaire has been proposed to 29 pediatric wards declaring over 10 malaria cases in 2000. Questions were focused on treatment practices and monitoring of children diagnosed with acute uncomplicated malaria in 2002. Results. – Twenty-six services, who treated more than 700 children, responded. Twenty-two on 26 services hospitalized systematically malaria cases. Mean duration of hospitalization was 2.2 days (S.D. ± 0.9). First line treatment was halofantrine in 22 on 26 services and mefloquine in four services. A second halofantrine dose was given systematically at day 7 in three services. No clinical cardiac effects happened. Quinine was used in perfusion only in cases of gastric intolerance. Treatment failure has never been experienced in the 22 services using halofantrine and has been experienced at least once in two on four wards using mefloquine. Relapse occurred at least once in 19 on 22 wards treating with halofantrine. Discussion. – Halofantrine with hospitalization is still the leading treatment of acute uncomplicated malaria in children in France. In spite of the absence of clinical cardiac incident, a second cure of halofantrine was not often used, exposing to a high rate of relapse. Mefloquine is three time more used than in 1997, in spite of its digestives side effects that can explain failures of treatment. When done, the systematic clinical and parasitological control confirms failures after mefloquine and the high incidence of relapse after one cure of halofantrine. Only used in case of severity or digestive disorders, quinine is a little less prescribed in acute uncomplicated malaria in 2001 than in 1997. Conclusions. – The limitations of antimalarial drugs used in France in case of acute malaria argue for an improvement of protocols (systematic second reduced dose of halofantrine after day 7, mefloquine associated with antiemetic drug) and a systematic clinical and parasitological monitoring. As alternative, efficient combinations of antimalarial as first line treatment are needed in France.

An open randomized clinical study of intrarectal versus infused Quinimax ® for the treatment of childhood cerebral malaria in Niger

The intrarectal route has been shown to be an alternative to parenteral therapy for the treatment of acute uncomplicated malaria. We conducted an open randomized clinical study of intrarectal Quinimax ® (a Cinchona alkaloids association) (20 mg/kg, then 15 mg/kg every 8 h) vs. intravenous Quinimax ® (8 mg/ kg infused over 4 h every 8 h) for 2 d in 76 children (39 in the intrarectal and 37 in the infusion groups) with cerebral falciparum malaria in Niger. This treatment was followed by oral chloroquine (10 mg/kg/d for 3 d).The primary end points of the study were fatal outcome and coma recovery time. In the intrarectal group, 35 children were cured (90%) and 4 died. In the infused group, 28 were cured (76%) and 9 died; mean coma recovery times were 34·6 h ( sd = 12·8) and 33·0 h ( sd = 14·1) for the intrarectal and infused groups, respectively. None of the differences was significant. Both treatments were well tolerated and no anal irritation was observed with intrarectal Quinimax ®. These findings suggest that intrarectal Quinimax ® can be an alternative to intravenous administration for rapid onset childhood cerebral malaria in the rural tropics, where the safety of parenteral administration cannot be guaranteed.

Clinical Studies of Atovaquone, Alone or in Combination with other Antimalarial Drugs, for Treatment of Acute Uncomplicated Malaria in Thailand

The therapy of Plasmodium falciparum malaria continues to be a problem in many parts of Southeast Asia because of multidrug resistance to nearly all existing antimalarial drugs. Atovaquone is a novel hydroxynaphthoquinone with broad spectrum anti-protozoal activity. We recently evaluated the antimalarial activity of atovaquone in a series of dose-ranging studies in 317 patients with malaria at the Bangkok Hospital for Tropical Diseases. Originally, the drug was administered alone. Using atovaquone alone resulted in satisfactory, initial clinical responses in all patients; the mean parasite and fever clearance times were 62 and 53 hr, respectively. However, irrespective of the duration of therapy, overall cure rates were approximately 67%. In vitro sensitivity studies on parasites taken from patients prior to treatment and at the time of recrudescence showed a marked decrease in susceptibility to atovaquone in the recrudescent parasites. To improve cure rates, atovaquone was administered in combination with other drugs with antimalarial activity. Proguanil and tetracycline were chosen due to laboratory evidence of potentiation; doxycycline was selected because it has a longer half-life than tetracycline. Although pyrimethamine did not show laboratory evidence of potentiation with atovaquone, it was chosen as an alternative inhibitor of dihydrofolic acid reductase with a longer half-life than proguanil. The clinical studies with these drug combinations confirmed the laboratory results with marked improvement in cure rates for proguanil, tetracycline, and doxycycline; pyrimethamine showed only minimal improvement. Proguanil was subsequently selected as the preferred drug partner because of its long record of safety and the ability to use the drug in pregnant women and children. Of the 104 patients with falciparum malaria treated with atovaquone plus proguanil for 3-7 days, 101 were cured and had virtually no adverse side effects. The combination of atovaquone and proguanil also was effective in eliminating erythrocytic forms of P. vivax, but parasitemia recurred in most patients.