Comparative efficacy of sulphadoxine-pyrimethamine and dihydroartemisinin-piperaquine against malaria infection during late-stage pregnancy in mice.

The introduction of artemisinin combination therapies (ACTs) against malaria infections opened up a window of possibilities to combat malaria in pregnancy. However, the usefulness of ACTs in all stages of pregnancy must be critically assessed. This study was designed to evaluate dihydroartemisinin-piperaquine (DHAP) as a suitable alternative to sulphadoxine-pyrimethamine (SP) in the treatment of malaria during third-trimester pregnancy in mice. Experimental animals were inoculated with a parasitic dose of 1x106Plasmodium berghei (ANKA strain) infected erythrocytes and randomly allocated into treatment groups. The animals received standard doses of chloroquine alone (CQ)[10 mg/kg], SP [25 mg/kg] and [1.25 mg/kg] and DHAP [4 mg/kg] and [18 mg/kg] combinations. Maternal and pupil survival, litter sizes, pup weight and still-births were recorded, while the effect of the drug combinations on parasite suppression, recrudescence and parasite clearance time were evaluated. The day 4 chemo-suppression of parasitemia by DHAP in infected animals was comparable to SP, and CQ treatment (P > 0.05). The mean recrudescence time was significantly delayed (P = 0.031) in the DHAP treatment group compared to the CQ treatment group, while, there was no recrudescence in animals treated with SP. The birth rate in the SP group was significantly higher than in the DHAP group (P < 0.05). There was 100% maternal and pup survival in both combination treatments comparable with the uninfected gravid controls. The overall parasitological activity of SP against Plasmodium berghei in late-stage pregnancy appeared better than DHAP. In addition, SP treatment resulted in better birth outcomes assessed compared to DHAP treatment.

Early rising asexual parasitaemia in Nigerian children following a first dose of artemisinin-based combination treatments of falciparum malaria.

BACKGROUND: Early rising asexual parasitaemia (ERAP), initially defined as 'an increase in the parasite count over the baseline pre-treatment level during the first 24 h of treatment' of falciparum malaria with artemisinin derivatives is well documented, but there is no characterization of its risk factors, kinetics, molecular features or relationship to late-appearing anaemia (LAA) in acute falciparum malaria in African children following oral artemisinin-based combination therapies (ACTs). METHODS: ERAP was defined as ≥5% increase in pre-treatment parasitaemia within 8 h of initiating treatment. Parasitaemia was quantified pre-treatment and 1-2 hourly for 8 h, and less frequently thereafter for 6 weeks following randomized treatment of acutely malarious children with artesunate-amodiaquine, artemether-lumefantrine or dihydroartemisinin-piperaquine. Risk factors were determined by stepwise multiple logistic regression model. Kinetics of release into and of elimination of asexual parasites and DNA clones from peripheral blood were evaluated by method of residuals and non-compartment model, respectively. Parasite population changes were evaluated morphologically and by molecular genotyping. RESULTS: ERAP occurred in 205 of 416 children. A parasitaemia <100,000/µL and parasitaemia 1 day post-treatment initiation were independent predictors of ERAP. In children with ERAP: mean and peak time of increase in parasitaemia were 105.6% (95% CI 81-130.1) and 2.5 h (95% CI 2.2-2.7), respectively. Mean lag time, half-time and rate constant of release were 0.2 h (95% CI 0.2-0.3), 1 h (95% CI 0.9-1.1), and 0.9 h-1 (95% CI 0.8-1), respectively. Schizonts and young gametocytes were seen only in peripheral blood of few children with ERAP. In age-, gender-, baseline parasitaemia- and treatment-matched children with and without ERAP, parasite DNA clearance time and area under curve of number of DNA clones versus time were significantly higher in children with ERAP indicating peripheral retention of released parasites followed by elimination. DNA clone elimination was monoexponential. CONCLUSION: ERAP is common, occurs rapidly as first order process and may be due to mobilization of parasites from deep tissue following a first dose of ACTs of acute childhood falciparum malaria. TRIALS REGISTRATION: Pan African Clinical Trial Registry PACTR201508001188143 , 3 July 2015; PACTR201510001189370, 3 July 2015; PACTR201508001191898, 7 July 2015 and PACTR201508001193368, 8 July 2015.

Factors contributing to anaemia after uncomplicated falciparum malaria in under five year-old Nigerian children ten years following adoption of artemisinin-based combination therapies as first-line antimalarials.

BACKGROUND: Artemisinin-based combination therapies (ACTs) have remained efficacious treatments of acute falciparum malaria in many endemic areas but there is little evaluation of factors contributing to the anaemia of acute falciparum malaria following long term adoption of ACTs as first-line antimalarials in African children. METHODS: Malarious <5 year-olds randomized to artemether-lumefantrine, artesunate-amodiaquine or dihydroartemisinin-piperaquine treatments were followed up clinically for 6 weeks. Anaemia was defined as haematocrit <30%; Malaria-attributable fall in haematocrit (MAFH) as the difference between haematocrit 28-42 days post- and pre-treatment; Total MAFH (TMAFH) as the difference between days 28-42 haematocrit and the lowest haematocrit recorded in the first week post-treatment initiation; Drug-attributable fall in haematocrit (DAFH) as the difference between MAFH and TMAFH; Early appearing anaemia (EAA) as haematocrit <30% occurring within 1 week in children with normal haematocrit pre-treatment. Predictors of anaemia pre-treatment, EAA, MAFH or DAFH >4% were evaluated by stepwise multiple logistic regression models. Survival analysis and kinetics of DAFH were evaluated by Kaplan-Meier estimator and non-compartment model, respectively. RESULTS: Pre-treatment, 355 of 959 children were anaemic. Duration of illness >2 days and parasitaemia ≤10,000 µL-1 were independent predictors of anaemia pre-treatment. EAA occurred in 301 of 604 children. Predictors of EAA were age ≤ 15 months, history of fever pre-treatment and enrolment haematocrit ≤35%. The probabilities of progression from normal haematocrit to EAA were similar for all treatments. MAFH >4% occurred in 446 of 694 children; its predictors were anaemia pre-treatment, enrolment parasitaemia ≤50,000 µL-1, parasitaemia one day post-treatment initiation and gametocytaemia. DAFH >4% occurred in 334 of 719 children; its predictors were history of fever pre-and fever 1 day post-treatment initiation, haematocrit ≥37%, and parasitaemia >100,000 µL-1. In 432 children, declines in DAFH deficits were monoexponential with overall estimated half-time of 2.2d (95% CI 1.9-2.6). Area under curve of deficits in DAFH versus time and estimated half-time were significantly higher in non-anaemic children indicating greater loss of haematocrit in these children. CONCLUSION: After ten years of adoption of ACTs, anaemia is common pre-and early post-treatment, falls in haematocrit attributable to a single infection is high, and DAFH >4% is common and significantly lower in anaemic compared to non-anaemic Nigerian children. TRIAL REGISTRATION: Pan African Clinical Trial Registry (PACTR) [ PACTR201709002064150, 1 March 2017 ].

Anaemia following Artemisinin-Based Combination Treatments of Uncomplicated Plasmodium falciparum Malaria in Children: Temporal Patterns of Haematocrit and the Use of Uncomplicated Hyperparasitaemia as a Model for Evaluating Late-Appearing Anaemia.

BACKGROUND: In severe malaria, intravenous artesunate may cause delayed haemolytic anaemia but there has been little evaluation of the propensity of oral artemisinin-based combination treatments (ACTs) to cause late-appearing anaemia. METHODS: The frequency of anaemia (haematocrit <30%), and temporal changes in haematocrit were evaluated in 1,191 malarious children following ACTs. "Haematocrit conservation" was evaluated by using the fall in haematocrit/1,000 asexual parasites cleared from the peripheral blood (FIH/1,000 asexual parasites cpb), and the ratio of the average haematocrit (on the first 3 days of starting treatment):total parasitaemia cleared. RESULTS: The frequency of anaemia decreased significantly following treatment. FIH/1,000 asexual parasites cpb, average haematocrit:total parasitaemia cleared, and mean haematocrit 5 weeks after treatment began were significantly lower in hyperparasitaemic children than in children without hyperparasitaemia, suggesting haematocrit conservation during treatment followed later by a loss of haematocrit. Asymptomatic late-appearing anaemia occurred in 6% of the children. CONCLUSION: Artesunate-amodiaquine and artemether-lumefantrine contribute to haematocrit conservation at high parasitaemias but may cause late-appearing anaemia.

Interaction between rifampicin, amodiaquine and artemether in mice infected with chloroquine resistant Plasmodium berghei.

BACKGROUND: Artemisinin-based combination therapy (ACT) remains the most effective chemotherapeutic strategy in the management of malaria. However, reports of reduced susceptibility of Plasmodium falciparum to the ACT justify the need for continued search for alternative anti-malarial drugs. The use of antibiotics with anti-malarial properties represents a potentially valuable chemotherapeutic option for the management of drug resistant infections. Thus, the intrinsic anti-malarial activity of the combination of clinical doses of rifampicin with amodiaquine and artemether was evaluated in an animal model using Plasmodium berghei. METHODS: A modification of the suppressive tests in vivo was employed. The anti-malarial activity of standard doses of amodiaquine (AQ) with or without artemether (ART) and combined with varying doses of rifampicin (RIF 15 mg/kg or RIF 30 mg/kg body weight) was evaluated in 40 mice sub-divided into eight groups and inoculated intraperitoneally with 1 × 10(7) red blood cells infected with chloroquine-resistant P. berghei ANKA strain. There were two control groups of animals, one group received amodiaquine alone while the other group received saline. Parasiticidal activity and survival of the animals were assessed over 21 days. RESULTS: Parasitaemia in the control animals peaked at 38% on day 9 and all animals died by day 10. The combination of amodiaquine with rifampicin 15 mg/kg body weight was the most effective of all the combinations and more efficacious than amodiaquine alone. The order of superiority of anti-malarial efficacy of the combinations was as follows; AQ + RIF 15 > AQ > AQ + ART + RIF 30 > AQ + ART + RIF 15 > AQ +RIF 30. CONCLUSION: The combination of the clinical dose of rifampicin (15 mg/kg) with amodiaquine represents a potentially valuable treatment option in management of drug resistant malaria. In addition, the role of pharmacokinetic interaction in multiple drug therapy cannot be over-emphasized.

Fall in hematocrit per 1000 parasites cleared from peripheral blood: a simple method for estimating drug-related fall in hematocrit after treatment of malaria infections.

A simple method to estimate antimalarial drug-related fall in hematocrit (FIH) after treatment of Plasmodium falciparum infections in the field is described. The method involves numeric estimation of the relative difference in hematocrit at baseline (pretreatment) and the first 1 or 2 days after treatment begun as numerator and the corresponding relative difference in parasitemia as the denominator, and expressing it per 1000 parasites cleared from peripheral blood. Using the method showed that FIH/1000 parasites cleared from peripheral blood (cpb) at 24 or 48 hours were similar in artemether-lumefantrine and artesunate-amodiaquine-treated children (0.09; 95% confidence interval, 0.052-0.138 vs 0.10; 95% confidence interval, 0.069-0.139%; P = 0.75) FIH/1000 parasites cpb in patients with higher parasitemias were significantly (P < 0.0001) and five- to 10-fold lower than in patients with lower parasitemias suggesting conservation of hematocrit or red cells in patients with higher parasitemias treated with artesunate-amodiaquine or artemether-lumefantrine. FIH/1000 parasites cpb were similar in anemic and nonanemic children. Estimation of FIH/1000 parasites cpb is simple, allows estimation of relatively conserved hematocrit during treatment, and can be used in both observational studies and clinical trials involving antimalarial drugs.

Therapeutic efficacy of artesunate-amodiaquine combinations and the plasma and saliva concentrations of desethylamodiaquine in children with acute uncomplicated Plasmodium falciparum malaria.

The treatment efficacy of artesunate-amodiaquine (AQ) coformulated or copackaged, and the plasma and saliva concentrations of desethylamodiaquine (DEAQ), the active metabolite of AQ, were evaluated in 120 and 7 children, respectively, with uncomplicated Plasmodium falciparum malaria treated with oral daily doses of the 2 formulations for 3 days. All children recovered clinically. Fever clearance (1.1 ± 0.2 vs 1.0 ± 0 days) and parasite clearance times (21.1 ± 10.2 vs 19.0 ± 7.0 hours) in artesunate-AQ coformulated and artesunate-AQ copackaged treated children, respectively, were similar. All children remained aparasitemic for at least 28 days. Blood and saliva samples were collected over 35 days and DEAQ in plasma and saliva was determined by high-performance liquid chromatography. DEAQ was detectable in plasma and saliva within 40 minutes of oral administration of artesunate-AQ. DEAQ concentrations 7 days after the start of therapy were 247.8 and 125.1 ng/mL in plasma and saliva, respectively. The concentration-time curves of plasma and saliva in declining phases were approximately parallel giving a similar half-life of 169.1 ± 16.4 and 142.8 ± 6.5 hours in plasma and saliva, respectively. Clearance from plasma and saliva was also similar (335.6 and 443.4 mL·h·kg, respectively). Area under concentration-time curves (AUC0-35d) for plasma and saliva were 94,744.9 and 74,004.2 ng·mL·h, respectively. In general, Saliva-plasma concentration ratio was 0.25-0.4. DEAQ concentrations in saliva may be useful for monitoring therapy and for the evaluation of the disposition of AQ in children with falciparum malaria treated with AQ-based combination.

In vitro-reduced susceptibility to artemether in P. falciparum and its association with polymorphisms on transporter genes.

Plasmodium falciparum with reduced sensitivity to artemisinin derivatives has been observed in endemic areas, but the molecular mechanisms for this reduced sensitivity remain unclear. We evaluated the association between in vitro susceptibility of P. falciparum isolates obtained from southwest Nigeria and polymorphisms in selected putative transporter genes (PFE0775C, PF13_0271, pfmrp1, pfcrt, and pfmdr1). Modified schizont inhibition assay was used to determine the in vitro parasite susceptibility to artemether (ATH). Polymorphisms in selected genes were detected by polymerase chain reaction followed by direct DNA sequencing. The half-maximal inhibitory concentration (IC(50)) geometric mean (GM) for all P. falciparum isolates was 1.78 nM (range, 0.03-10.43 nM). Polymorphisms at codons 241, 86, and 76 of PFE0775C, pfmdr1, and pfcrt genes, respectively, were associated with reduced susceptibility to ATH. A new S263P single-nucleotide polymorphism on the PFE0775C gene was also detected in 27% of the isolates. Patient isolates harboring V241L or S263P polymorphisms on the PFE0775C gene showed increased IC(50) (GM: 3.08 nM and 1.79 nM, respectively). Plasmodium falciparum isolates harboring mutant Y86 pfmdr1 and P263 PFE0775C alleles showed a 2.5-5.5-fold increase in ATH IC(50.) This study shows that polymorphisms on the PFE0775C and pfmdr1 genes are associated with reduced sensitivity to ATH in fresh isolates of P. falciparum from Nigeria.

A high performance liquid chromatographic assay of mefloquine in saliva after a single oral dose in healthy adult Africans.

BACKGROUND: Mefloquine-artesunate is a formulation of artemisinin based combination therapy (ACT) recommended by the World Health Organization and historically the first ACT used clinically. The use of ACT demands constant monitoring of therapeutic efficacies and drug levels, in order to ensure that optimum drug exposure is achieved and detect reduced susceptibility to these drugs. Quantification of anti-malarial drugs in biological fluids other than blood would provide a more readily applicable method of therapeutic drug monitoring in developing endemic countries. Efforts in this study were devoted to the development of a simple, field applicable, non-invasive method for assay of mefloquine in saliva. METHODS: A high performance liquid chromatographic method with UV detection at 220 nm for assaying mefloquine in saliva was developed and validated by comparing mefloquine concentrations in saliva and plasma samples from four healthy volunteers who received single oral dose of mefloquine. Verapamil was used as internal standard. Chromatographic separation was achieved using a Hypersil ODS column. RESULTS: Extraction recoveries of mefloquine in plasma or saliva were 76-86% or 83-93% respectively. Limit of quantification of mefloquine was 20 ng/ml. Agreement between salivary and plasma mefloquine concentrations was satisfactory (r = 0.88, p < 0.001). Saliva:plasma concentrations ratio was 0.42. CONCLUSION: Disposition of mefloquine in saliva paralleled that in plasma, making salivary quantification of mefloquine potentially useful in therapeutic drug monitoring.

Pharmacokinetic disposition of sulfadoxine in children with acute uncomplicated falciparum malaria treated with sulfadoxine-pyrimethamine in South West Nigeria.

Sulfadoxine (SDX)-pyrimethamine is currently recommended as a partner drug with artesunate in the chemotherapy of malaria. However, information on pharmacokinetic disposition of SDX-pyrimethamine in children is limited. Efforts in this study were thus devoted to evaluation of pharmacokinetic disposition of SDX using high-pressure liquid chromatographic techniques and effects of pharmacokinetic variability on treatment outcome in Nigerian children with falciparum malaria. The blood concentration profile of SDX was similar in patients whose infection responded to treatment and those who failed treatment; mean SDX concentration values were similar for day 3 (179 vs 157 µg/mL, P = 0.734), day 7 (84 vs 51 µg/mL, P = 0.365), and day 14 (50 vs 14 µg/mL, P = 0.151). Extent of exposure (area under the curve) to SDX was also similar in the patients (1196 vs 1013 µg d/mL, P = 0.561). Pearson's correlation, showed significant correlation between area under the curve and D3 or D7 concentration of SDX (P = 0.001, r = 0.702 or P = 0.001, r = 0.835, respectively). Age-stratified analysis showed that SDX concentrations were significantly higher in older children (older than 5 years); the mean maximum concentration (125 vs 295 µg/mL, P = 0.001), extent of exposure (812 vs 1562 µg d/mL, P = 0.001), day 3 concentration (98 vs 250 µg/mL, P = 0.001), and day 7 concentration (54 vs 128 µg/mL, P = 0.007) were higher. The study revealed no differences in posttreatment blood SDX concentrations in patients who responded to treatment and those who failed to respond to treatment. Furthermore, there was an age-related pharmacokinetic variability of SDX in the group of children studied with potential impact on treatment outcome.

A simple dose regimen of artesunate and amodiaquine based on age or body weight range for uncomplicated falciparum malaria in children: comparison of therapeutic efficacy with standard dose regimen of artesunate and amodiaquine and artemether-lumefantrine.

A new dose regimen of artesunate and amodiaquine (NDRAA) based on age or body weight range was compared with standard dose regimen of artesunate and amodiaquine (SDRAA) calculated according to body weight and with fixed-dose artesunate-amodiaquine (FDAA) and artemether-lumefantrine (AL) in 304 children afflicted by malaria aged 15 years or younger. In initial comparison (n = 208), children on NDRAA received 1-3 times amodiaquine per kilogram of body weight and 1-1.5 times of artesunate per kilogram of body weight compared with those receiving SDRAA. Parasite but not fever clearance was significantly faster in children who received NDRAA (19.4 ± 8.4 hours vs. 24.6 ± 15.5 hours, P = 0.003). Polymerase chain reaction-uncorrected cure rates on days 28-42 were also significantly higher in children who received NDRAA (P < 0.02 in all cases). Therapeutic responses in children younger than 5 years (n = 96) treated with NDRAA, FDAA, and AL were similar. Changes in hematocrit values and reported adverse events after commencing therapy were similar in those who received NDRAA and SDRAA. All drug regimens were well tolerated. NDRAA based on age or body weight range is simple, is therapeutically superior to SDRAA calculated according to body weight, and is as efficacious as AL in children younger than 5 years.

Interaction between ciprofloxacin and chloroquine in mice infected with chloroquine resistant Plasmodium berghei: interaction between ciprofloxacin and chloroqune.

The increasing spread of chloroquine resistant malaria has intensified the search for new antimalarial treatment, especially drugs that can be used in combination. Ciprofloxacin (CFX) a fluoroquinolone commonly used to treat bacterial infections has been shown to possess significant antimalarial activity both in vitro and in vivo. Thus efforts in this study were devoted to evaluating the antimalarial activity of combination of chloroquine (CQ) with varying doses (10, 20, 40 80, 160 mg/kg body weight) of CFX in groups of 35 mice inoculated intraperitoneally with 10(7) chloroquine resistant strain Plasmodium berghei ANKA. Parasitological activity and survival of the animals were assessed over 21 days. Parasitemia in non-treated control mice peaked at 78% on day 9 and none survived by day 10. However, the combination of CQ with 160 mg/kg body weight of CFX resulted in a reduction in parasitemia between days 9 and 14 and this was significantly lower than that obtained with CQ alone or CQ combined with the lower doses of CFX (p < 0.05). In addition, the combination of CQ with 160 mg/kg CFX significantly reduced mortality in the infected animals (p = 0.0002) compared with the other treatment groups. The results from this study support the potential usefulness of CFX in combination with antimalarial drugs for the treatment of chloroquine resistant human malaria.

Antitrypanosomal activity of some medicinal plants from Nigerian ethnomedicine.

Human African trypanosomiasis is a neglected tropical disease with complex clinical presentation, diagnosis, and difficult treatment. The available drugs for the treatment of trypanosomiasis are old, expensive, and less effective, associated with severe adverse reactions and face the problem of drug resistance. This situation underlines the urgent need for the development of new, effective, cheap, and safe drugs for the treatment of trypanosomiasis. The search for new antitrypanosomal agents in this study is based on ethnomedicine. In vitro antitrypanosomal activity of 36 plant extracts from 10 plant species from Nigerian ethnomedicine was evaluated against bloodstream forms of Trypanosoma brucei rhodesiense STIB 900. Cytotoxic activity was determined against mammalian L6 cells. Alamar blue assay was used to measure the endpoint of both antitrypanosomal and toxicity assays. The ethyl acetate extract of leaves of Ocimum gratissimum Linn. (Labiatae) showed the highest antitrypanosomal activity (IC(50) of 2.08 ± 0.01 µg/ml) and a high selective index of 29. Furthermore, the hexane, ethyl acetate, or methanol extracts of Trema orientalis (L.) Blume (Ulmaceae), Pericopsis laxiflora (Benth. ex Baker) Meeuwen, Jatropha curcas Linn. (Euphorbiaceae), Terminalia catappa Linn. (Combretaceae), and Vitex doniana Sweet (Verbenaceae) displayed remarkable antitrypanosomal activity (IC(50) 2.1-17.2 µg/ml) with high selectivity indices (20-80) for trypanosomes. The antitrypanosomal activity of T. catappa and T. orientalis against T. brucei rhodesiense (STIB 900) is being reported for the first time in Nigerian ethnomedicine, and these plants could be a potential source of antitrypanosomal agents.

Oral artesunate-amodiaquine and artemether-lumefantrine in the treatment of uncomplicated hyperparasitaemic Plasmodium falciparum malaria in children.

The therapeutic efficacy, changes in haematocrit and declines in parasitaemias were evaluated in 56 children with uncomplicated falciparum hyperparasitaemia after oral artesunate-amodiaquine or artemether-lumefantrine. All children recovered clinically within 2 days and without progression to severe malaria. Falls in haematocrit in the first 3 days after treatment began were similar and <5%. Declines in parasitaemias were monoexponential with both treatments with an estimated half-life of 1 h.

A simple dose regimen of artesunate and amodiaquine based on arm span- or age range for childhood falciparum malaria: a preliminary evaluation.

A dose regimen of artesunate and amodiaquine based on arm span- or age range (DRAAAS), derived from a study of 1674 children, was compared with standard dose regimen of the same drugs calculated according to body weight (SDRAA) in 68 malarious children. Children on DRAAAS received 0.8-1.0 of artesunate/kg and 0.9-1.2 times amodiaquine/kg compared with those receiving SDRAA. Parasite and fever clearance and fall in hematocrit in the first 3 days were similar; both regimens were well tolerated. DRAAAS is simple and is efficacious.

Risk factors for Plasmodium falciparum hyperparasitaemia in malarious children.

BACKGROUND: Hyperparasitaemia is a feature of childhood severe malaria but there is little information on the risk factors for hyperparasitaemia in malarious children METHODS: The risk factors associated with Plasmodium falciparum hyperparasitaemia, defined as asexual parasitaemia > 250,000/µl, at presentation were evaluated in 3338 malarious children enrolled prospectively between 2008 and 2010 in an endemic area of southwestern Nigeria. RESULTS: At enrolment, 97 (3%) of 3338 malarious children had hyperparasitaemia. In a multiple regression model, 3 factors were found to be independent risk factors for the presence of hyperparasitaemia at enrolment: an age ≤ 11 years (Adjusted odds ratio [AOR] = 2.85, 95% confidence interval [CI] 1.23-6.61, P = 0.014), fever (AOR = 2.02, 95% CI 1.23-3.29, P = 0.005), and enrolment after year 2008 (AOR = 0.42, 95% CI 0.24-0.73, P = 0.002). Duration of illness ≤ 3 d was associated with increased risk of hyperparasitaemia. There was no association between season and hyperparasitaemia. Compared to non-hyperparasitaemia, hyperparasitaemia was associated with an increased risk of progression to cerebral malaria (P < 0.0001). The risk of progression in hyperparasitaemic children was higher in < 5-year olds (P = 0.02). CONCLUSION: Young age and presence of fever are independent risk factors for hyperparasitaemia which is associated with an increased risk of progression to cerebral malaria. The findings have implications for case and community management of childhood hyperparasitaemia and for malaria control efforts in sub-Saharan Africa where severe malaria is relatively common.

Use of area under the curve to evaluate the effects of antimalarial drugs on malaria-associated anemia after treatment.

To evaluate the effects of antimalarial drugs on Plasmodium falciparum malaria-associated anemia, we use the area under the curve (AUC) of anemia levels after treatment as an approach to combine their duration and magnitude. The method involves numeric estimation, by trapezoidal rule, of AUC from a plot of deficit in hematocrit levels from 30% (the lower threshold of normal) versus time in anemic children. Using the method, we evaluated, in randomized trials, the effects of artesunate-mefloquine versus mefloquine alone and artemether-lumefantrine versus amodiaquine-artesunate on the time course of recovery from malaria-associated anemia in 109 children. Anemia resolution times were similar (10.9 ± 6.2 [standard deviation] versus 13.3 ± 8.9 days, P = 0.2), but mean AUC was significantly lower in artesunate-mefloquine- compared with mefloquine-treated children (35.5 ± 7.1 [standard error of mean] versus 49.8 ± 11.3 %·h, P = 0.02) indicating larger exposure to anemia in mefloquine-treated children. In artemether-lumefantrine- and amodiaquine-artesunate-treated children, both anemia resolution times (8.6 ± 5.3 [standard deviation] versus 8.6 ± 4.8 days, P = 0.98) and mean AUC (57.1 ± 12.9 [standard error of mean] versus 46.3 ± 8.7 %·h, P = 0.74) were similar. Estimation of AUC appears more robust than estimation of anemia resolution time in evaluating antimalarial drug effects and can be used in both observational studies and clinical trials assessing the effects of therapies on malaria-associated anemia.

Risk factors for gametocyte carriage in uncomplicated falciparum malaria in children before and after artemisinin-based combination treatments.

BACKGROUND: Artemisinin-based combination treatments (ACTs) are the recommended first-line antimalarials globally, but their influence on the risk factors associated with gametocyte carriage has had little evaluation in endemic areas. METHODS: The risk factors associated with gametocytaemia at presentation and after ACTs were evaluated in 835 children assigned to artesunate, artesunate-amodiaquine, artesunate-mefloquine or artemether-lumefantrine. RESULTS: Gametocyte carriage at enrolment was 8.4%. During follow-up, 24 patients (2.8%) developed gametocytaemia, which in 83% (20 patients) had developed by day 7 following treatment. In a multiple regression model, 2 factors were independent risk factors for the presence of gametocytaemia at enrolment, namely age <3 years (adjusted odds ratio 2.03, 95% confidence interval 1.01-4.05; p = 0.04) and enrolment before 2009 (adjusted odds ratio 4.2, 95% confidence interval 2.09-8.44; p < 0.001). Haematocrit <25% and parasitaemia <50,000/µl blood were associated with an increased risk of gametocytaemia. Following treatment, 3 factors were independent risk factors for gametocytaemia, namely gametocytaemia at enrolment (adjusted odds ratio 46.39, 95% confidence interval 22.3-96.46; p < 0.0001) and treatment with artesunate (adjusted odds ratio 6.74, 95% confidence interval 1.79-25.27; p = 0.005) or artesunate-mefloquine (adjusted odds ratio 9.66, 95% confidence interval 2.87-32.46; p < 0.0.0001) relative to other ACTs. CONCLUSION: ACTs modified the risk factors associated with gametocyte carriage after use.

Plasmodium falciparum gametocyte carriage, sex ratios and asexual parasite rates in Nigerian children before and after a treatment protocol policy change instituting the use of artemisinin-based combination therapies.

The effects of artemisinin-based combination therapies (ACTs) on transmission of Plasmodium falciparum were evaluated after a policy change instituting the use of ACTs in an endemic area. P. falciparum gametocyte carriage, sex ratios and inbreeding rates were examined in 2,585 children at presentation with acute falciparum malaria during a 10-year period from 2001-2010. Asexual parasite rates were also evaluated from 2003-2010 in 10,615 children before and after the policy change. Gametocyte carriage declined significantly from 12.4% in 2001 to 3.6% in 2010 (χ2 for trend = 44.3, p < 0.0001), but sex ratios and inbreeding rates remained unchanged. Additionally, overall parasite rates remained unchanged before and after the policy change (47.2% vs. 45.4%), but these rates declined significantly from 2003-2010 (χ2 for trend 35.4, p < 0.0001). Chloroquine (CQ) and artemether-lumefantrine (AL) were used as prototype drugs before and after the policy change, respectively. AL significantly shortened the duration of male gametocyte carriage in individual patients after treatment began compared with CQ (log rank statistic = 7.92, p = 0.005). ACTs reduced the rate of gametocyte carriage in children with acute falciparum infections at presentation and shortened the duration of male gametocyte carriage after treatment. However, parasite population sex ratios, inbreeding rates and overall parasite rate were unaffected.

Plasmodium falciparum gametocyte carriage, emergence, clearance and population sex ratios in anaemic and non-anaemic malarious children.

Anaemia in falciparum malaria is associated with an increased risk of gametocyte carriage, but its effects on transmission have not been extensively evaluated in malarious children. Plasmodium falciparum gametocyte carriage, emergence, clearance, population sex ratios (SR) (defined as the proportion of gametocytes that are male), inbreeding rates and temporal changes in SR were evaluated in 840 malarious children. Gametocyte carriage pre-treatment was at a level of 8.1%. Anaemia at enrolment was an independent risk factor for gametocyte carriage post-treatment. The emergence of gametocytes seven days post-treatment was significantly more frequent in anaemic children (7/106 vs. 10/696, p = 0.002). In the initially detected gametocytes, the proportion of children with a male-biased SR (MBSR) (> 0.5) was significantly higher in anaemic children (6/7 vs. 3/10, p = 0.027). Pre-treatment SR and estimated inbreeding rates (proportion of a mother's daughters fertilised by her sons) were similar in anaemic and non-anaemic children. Pre-treatment SR became more female-biased in non-anaemic children following treatment. However, in anaemic children, SR became male-biased. Anaemia was shown to significantly increase gametocyte emergence and may significantly alter the SR of emerging gametocytes. If MBSR is more infective to mosquitoes at low gametocytaemia, then these findings may have significant implications for malaria control efforts in endemic settings where malaria-associated anaemia is common.