Grant Dorsey

Polymorphisms in the Plasmodium falciparum pfcrt and pfmdr-1 genes and clinical response to chloroquine in Kampala, Uganda

The molecular mechanism of chloroquine resistance in Plasmodium falciparum remains uncertain. Polymorphisms in the pfcrt and pfmdr-1 genes have been associated with chloroquine resistance in vitro, although field studies are limited. In evaluations of known polymorphisms in parasites from patients with uncomplicated malaria in Kampala, Uganda, the presence of 8 pfcrt mutations and 2 pfmdr-1 mutations did not correlate with clinical response to therapy with chloroquine. Most notably, the pfcrt lysine-->threonine mutation at position 76, which recently correlated fully with chloroquine resistance in vitro, was present in 100% of 114 isolates, of which about half were from patients who recovered clinically after chloroquine therapy. These results suggest that, although key pfcrt polymorphisms may be necessary for the elaboration of resistance to chloroquine in areas with high levels of chloroquine resistance, other factors, such as host immunity, may contribute to clinical outcomes.

Sulfadoxine/pyrimethamine alone or with amodiaquine or artesunate for treatment of uncomplicated malaria: a longitudinal randomised trial.

BACKGROUND New antimalarial treatments are urgently needed in sub-Saharan Africa. Improved therapies should decrease failure rates in the short term, but their effect on incidence of subsequent episodes of malaria is little studied. We aimed to compare the short-term and long-term effectiveness of three antimalarial regimens in children from Kampala, Uganda. METHODS We randomly allocated healthy children aged 6 months to 5 years to receive 25 mg/kg sulfadoxine and 1.25 mg/kg pyrimethamine plus either placebo, 25 mg/kg amodiaquine, or 12 mg/kg artesunate. Participants were followed up for 1 year and received the same preassigned treatment for every new episode of uncomplicated malaria diagnosed during follow-up. Recrudescent and new infections were distinguished by comparison of polymorphisms in merozoite surface protein 2 (MSP2). Our primary endpoint was the total number of treatments for malaria per time at risk. Analyses were done per protocol. FINDINGS 183 (61%) of 316 participants were diagnosed with at least one episode of uncomplicated malaria. A total of 577 episodes of uncomplicated Plasmodium falciparum malaria were treated with study drugs; all regimens were safe and well tolerated. Clinical treatment failure after 14 days was significantly more frequent in the sulfadoxine/pyrimethamine group (38 of 215, 18%) compared with either the sulfadoxine/pyrimethamine plus amodiaquine group (two of 164, 1%; p<0.0001) or sulfadoxine/pyrimethamine plus artesunate group (one of 198, 1%; p<0.0001). After 28 and 42 days, patients in the sulfadoxine/pyrimethamine plus amodiaquine group were significantly less likely to develop malaria than were those in the other groups. Overall, sulfadoxine/pyrimethamine plus amodiaquine reduced the rate of subsequent treatments for malaria by 54% (95% CI 36-66, p<0.0001) compared with sulfadoxine/ pyrimethamine alone and by 37% (12-54, p=0.007) compared with sulfadoxine/pyrimethamine plus artesunate. INTERPRETATION Sulfadoxine/pyrimethamine plus amodiaquine could be used as an inexpensive regimen to decrease the rate of subsequent episodes of malaria.

Effect of HIV-1 Infection on Antimalarial Treatment Outcomes in Uganda: A Population-Based Study

BACKGROUND Human immunodeficiency virus (HIV) infection may increase the burden of malaria by increasing susceptibility to infection or by decreasing the response to antimalarial treatment. We investigated the seroprevalence rate of HIV-1 infection and its effect on antimalarial treatment outcomes in adults and children with uncomplicated falciparum malaria in Uganda. METHODS This retrospective study included 1965 patients > or =18 months old who were randomized to receive 1 of 3 antimalarial regimens at 7 sites in Uganda. HIV-1 testing was performed using 2 enzyme-linked immunosorbent assays and Western blot analysis of stored blood spots. The primary study outcome was clinical treatment failure at 28 days after antimalarial treatment. Molecular genotyping was used to distinguish clinical treatment failures due to new infections from those due to recrudescences. RESULTS The HIV-1 seroprevalence rate was 2.5% in 1802 patients <18 years old and 31% in 163 patients > or =18 years old presenting with malaria. HIV-1 infection was associated with a >3-fold (hazard ratio [HR], 3.28 [95% confidence interval [CI], 1.25-8.59]) increased risk of clinical treatment failure for adults, but there was no increased risk for HIV-1-infected children. Molecular genotyping revealed that clinical treatment failures were due to new infections (HR, 6.35 [95% CI, 1.64-24.5]) rather than to recrudescences (HR, 1.51 [95% CI, 0.27-8.58]). CONCLUSIONS The HIV-1 seroprevalence rate was surprisingly high in adults presenting with malaria. This finding supports the implementation of routine HIV counseling and testing for adults with uncomplicated falciparum malaria. HIV-1 infection increased the susceptibility to new malarial infections but did not increase the risk of recrudescences in adults.

Selection of Plasmodium falciparum pfmdr1 Alleles following Therapy with Artemether-Lumefantrine in an Area of Uganda where Malaria Is Highly Endemic

ABSTRACT Polymorphisms in the Plasmodium falciparum pfmdr1 gene were assayed in pretreatment samples and in samples from patients reinfected following therapy with artemether-lumefantrine. The pfmdr1 alleles 86N, 184F, and 1246D significantly increased in prevalence after treatment. All samples had a single pfmdr1 copy. Treatment with artemether-lumefantrine selects for polymorphisms that may alter antimalarial drug response.

Artemether-Lumefantrine versus Dihydroartemisinin-Piperaquine for Treatment of Malaria: A Randomized Trial

Objectives: To compare the efficacy and safety of artemether-lumefantrine (AL) and dihydroartemisinin-piperaquine (DP) for treating uncomplicated falciparum malaria in Uganda. Design: Randomized single-blinded clinical trial. Setting: Apac, Uganda, an area of very high malaria transmission intensity. Participants: Children aged 6 mo to 10 y with uncomplicated falciparum malaria. Intervention: Treatment of malaria with AL or DP, each following standard 3-d dosing regimens. Outcome measures: Risks of recurrent parasitemia at 28 and 42 d, unadjusted and adjusted by genotyping to distinguish recrudescences and new infections. Results: Of 421 enrolled participants, 417 (99%) completed follow-up. The unadjusted risk of recurrent falciparum parasitemia was significantly lower for participants treated with DP than for those treated with AL after 28 d (11% versus 29%; risk difference [RD] 18%, 95% confidence interval [CI] 11%–26%) and 42 d (43% versus 53%; RD 9.6%, 95% CI 0%–19%) of follow-up. Similarly, the risk of recurrent parasitemia due to possible recrudescence (adjusted by genotyping) was significantly lower for participants treated with DP than for those treated with AL after 28 d (1.9% versus 8.9%; RD 7.0%, 95% CI 2.5%–12%) and 42 d (6.9% versus 16%; RD 9.5%, 95% CI 2.8%–16%). Patients treated with DP had a lower risk of recurrent parasitemia due to non-falciparum species, development of gametocytemia, and higher mean increase in hemoglobin compared to patients treated with AL. Both drugs were well tolerated; serious adverse events were uncommon and unrelated to study drugs. Conclusion: DP was superior to AL for reducing the risk of recurrent parasitemia and gametocytemia, and provided improved hemoglobin recovery. DP thus appears to be a good alternative to AL as first-line treatment of uncomplicated malaria in Uganda. To maximize the benefit of artemisinin-based combination therapy in Africa, treatment should be integrated with aggressive strategies to reduce malaria transmission intensity.

In vivo parasitological measures of artemisinin susceptibility.

Parasite clearance data from 18,699 patients with falciparum malaria treated with an artemisinin derivative in areas of low (n=14,539), moderate (n=2077), and high (n=2083) levels of malaria transmission across the world were analyzed to determine the factors that affect clearance rates and identify a simple in vivo screening measure for artemisinin resistance. The main factor affecting parasite clearance time was parasite density on admission. Clearance rates were faster in high-transmission settings and with more effective partner drugs in artemisinin-based combination treatments (ACTs). The result of the malaria blood smear on day 3 (72 h) was a good predictor of subsequent treatment failure and provides a simple screening measure for artemisinin resistance. Artemisinin resistance is highly unlikely if the proportion of patients with parasite densities of <100,000 parasites/microL given the currently recommended 3-day ACT who have a positive smear result on day 3 is <3%; that is, for n patients the observed number with a positive smear result on day 3 does not exceed (n + 60)/24.

Rapid Diagnostic Tests for Malaria at Sites of Varying Transmission Intensity in Uganda

BACKGROUND In Africa, fever is often treated presumptively as malaria, resulting in misdiagnosis and the overuse of antimalarial drugs. Rapid diagnostic tests (RDTs) for malaria may allow improved fever management. METHODS We compared RDTs based on histidine-rich protein 2 (HRP2) and RDTs based on Plasmodium lactate dehydrogenase (pLDH) with expert microscopy and PCR-corrected microscopy for 7000 patients at sites of varying malaria transmission intensity across Uganda. RESULTS When all sites were considered, the sensitivity of the HRP2-based test was 97% when compared with microscopy and 98% when corrected by PCR; the sensitivity of the pLDH-based test was 88% when compared with microscopy and 77% when corrected by PCR. The specificity of the HRP2-based test was 71% when compared with microscopy and 88% when corrected by PCR; the specificity of the pLDH-based test was 92% when compared with microscopy and >98% when corrected by PCR. Based on Plasmodium falciparum PCR-corrected microscopy, the positive predictive value (PPV) of the HRP2-based test was high (93%) at all but the site with the lowest transmission rate; the pLDH-based test and expert microscopy offered excellent PPVs (98%) for all sites. The negative predictive value (NPV) of the HRP2-based test was consistently high (>97%); in contrast, the NPV for the pLDH-based test dropped significantly (from 98% to 66%) as transmission intensity increased, and the NPV for expert microscopy decreased significantly (99% to 54%) because of increasing failure to detect subpatent parasitemia. CONCLUSIONS Based on the high PPV and NPV, HRP2-based RDTs are likely to be the best diagnostic choice for areas with medium-to-high malaria transmission rates in Africa.

Artemether-Lumefantrine versus Dihydroartemisinin-Piperaquine for Treating Uncomplicated Malaria: A Randomized Trial to Guide Policy in Uganda

Background Uganda recently adopted artemether-lumefantrine (AL) as the recommended first-line treatment for uncomplicated malaria. However, AL has several limitations, including a twice-daily dosing regimen, recommendation for administration with fatty food, and a high risk of reinfection soon after therapy in high transmission areas. Dihydroartemisinin-piperaquine (DP) is a new alternative artemisinin-based combination therapy that is dosed once daily and has a long post-treatment prophylactic effect. We compared the efficacy and safety of AL with DP in Kanungu, an area of moderate malaria transmission. Methodology/Principal Findings Patients aged 6 months to 10 years with uncomplicated falciparum malaria were randomized to therapy and followed for 42 days. Genotyping was used to distinguish recrudescence from new infection. Of 414 patients enrolled, 408 completed follow-up. Compared to patients treated with artemether-lumefantrine, patients treated with dihydroartemisinin-piperaquine had a significantly lower risk of recurrent parasitaemia (33.2% vs. 12.2%; risk difference = 20.9%, 95% CI 13.0–28.8%) but no statistically significant difference in the risk of treatment failure due to recrudescence (5.8% vs. 2.0%; risk difference = 3.8%, 95% CI −0.2–7.8%). Patients treated with dihydroartemisinin-piperaquine also had a lower risk of developing gametocytaemia after therapy (4.2% vs. 10.6%, p = 0.01). Both drugs were safe and well tolerated. Conclusions/Significance DP is highly efficacious, and operationally preferable to AL because of a less intensive dosing schedule and requirements. Dihydroartemisinin-piperaquine should be considered for a role in the antimalarial treatment policy of Uganda. Trial Registration Controlled-Trials.com ISRCTN75606663

Artemisinin versus Nonartemisinin Combination Therapy for Uncomplicated Malaria: Randomized Clinical Trials from Four Sites in Uganda

Background Drug resistance in Plasmodium falciparum poses a major threat to malaria control. Combination antimalarial therapy including artemisinins has been advocated recently to improve efficacy and limit the spread of resistance, but artemisinins are expensive and relatively untested in highly endemic areas. We compared artemisinin-based and other combination therapies in four districts in Uganda with varying transmission intensity. Methods and Findings We enrolled 2,160 patients aged 6 mo or greater with uncomplicated falciparum malaria. Patients were randomized to receive chloroquine (CQ) + sulfadoxine-pyrimethamine (SP); amodiaquine (AQ) + SP; or AQ + artesunate (AS). Primary endpoints were the 28-d risks of parasitological failure either unadjusted or adjusted by genotyping to distinguish recrudescence from new infections. A total of 2,081 patients completed follow-up, of which 1,749 (84%) were under the age of 5 y. The risk of recrudescence after treatment with CQ + SP was high, ranging from 22% to 46% at the four sites. This risk was significantly lower (p < 0.01) after AQ + SP or AQ + AS (7%–18% and 4%–12%, respectively). Compared to AQ + SP, AQ + AS was associated with a lower risk of recrudescence but a higher risk of new infection. The overall risk of repeat therapy due to any recurrent infection (recrudescence or new infection) was similar at two sites and significantly higher for AQ + AS at the two highest transmission sites (risk differences = 15% and 16%, p< 0.003). Conclusion AQ + AS was the most efficacious regimen for preventing recrudescence, but this benefit was outweighed by an increased risk of new infection. Considering all recurrent infections, the efficacy of AQ + SP was at least as efficacious at all sites and superior to AQ + AS at the highest transmission sites. The high endemicity of malaria in Africa may impact on the efficacy of artemisinin-based combination therapy. The registration number for this trial is ISRCTN67520427 (http://www.controlled-trials.com/isrctn/trial/|/0/67520427.html).

Malaria in Uganda: challenges to control on the long road to elimination: I. Epidemiology and current control efforts.

Malaria remains one of the leading health problems of the developing world, and Uganda bears a particularly large burden from the disease. Our understanding is limited by a lack of reliable data, but it is clear that the prevalence of malaria infection, incidence of disease, and mortality from severe malaria all remain very high. Uganda has made progress in implementing key malaria control measures, in particular distribution of insecticide-impregnated bednets, indoor residual spraying of insecticides, utilization of artemisinin-based combination therapy to treat uncomplicated malaria, and provision of intermittent preventive therapy for pregnant women. However, despite enthusiasm regarding the potential for the elimination of malaria in other areas, there is no convincing evidence that the burden of malaria has decreased in Uganda in recent years. Major challenges to malaria control in Uganda include very high malaria transmission intensity, inadequate health care resources, a weak health system, inadequate understanding of malaria epidemiology and the impact of control interventions, increasing resistance of parasites to drugs and of mosquitoes to insecticides, inappropriate case management, inadequate utilization of drugs to prevent malaria, and inadequate epidemic preparedness and response. Despite these challenges, prospects for the control of malaria have improved, and with attention to underlying challenges, progress toward the control of malaria in Uganda can be expected.