41 research outputs found
Early Changes in Plasmodium falciparum Asexual and Sexual Populations in Children with Acute Infections Following Treatment with Artemisinin-Based Combination Drugs
Artemisinin-based combination therapies (ACTs)
may influence malaria transmission but the early changes
in parasite populations have not been frequently evaluated.
The changes in Plasmodium falciparum asexual and sexual
populations in the first 16 h following treatment with
artemether-lumefantrine (AL) or artesunate-amodiaquine
(AA) were evaluated in 443 children with acute infections.
The effects of gametocyte density on gametocyte sex ratio
(GSR) were characterized in another cohort of 52 children
treated with AL and AA. Stages of asexual and sexual
parasites in peripheral blood were determined morphologically.
In 167 children there were significant increases in
peripheral asexual parasitemia at 1 h, and in 15 of these,
an insignificant increase in gametocytemia at 1 h, followed
thereafter by a precipitous and significant fall in all patients.
Time-course of GSR showed a female-male-female-biased
cycle at 0 h, 4 h, and 8 h. Pre-treatment GSR and time-course
of GSR post-treatment were independent of density in the
additional cohort of 52 gametocyte carriers treated with AL
or AA. Population changes were similar in AL- and AAtreated
children. Treatment with AL or AA is associated
with early increases in asexual and sexual parasites and is
closely followed by rapid elimination of these parasites
Temporal changes in haematocrit following artemisinin-based combination treatments of uncomplicated falciparum malaria in children
Semilog plots of deficit in haematocrit from 30Ă‚Â % versus time in children with haematocrit <30Ă‚Â % at presentation (Pattern 6). (DOCX 16 kb
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
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
Recrudescent Plasmodium falciparum infections in children in an endemic area following artemisinin–based combination treatments: Implications for disease control
To evaluate the features and risk factors associated with recrudescent infections that arose following artemisinin-based combination drug treatment of the primary infections.
Methods
The clinical features and risk factors associated with subsequent recrudescence of primary Plasmodium falciparum infections were evaluated in 37 of 877 children following artesunate or artemisinin-based combination treatments (ACTs). Recrudescence was determined by polymerase chain reaction
Therapeutic Efficacy and Effects of Artesunate-Mefloquine and Mefloquine Alone on Malaria-Associated Anemia in Children with Uncomplicated Plasmodium falciparum Malaria in Southwest Nigeria
The treatment efficacy and effects of artesunate-mefloquine (AMQ) and mefloquine (MQ) on malariaassociated
anemia (MAA) were evaluated in 342 children ≤ 10 years of age with uncomplicated Plasmodium falciparum
malaria randomized to receive either drug/drug combination. All children recovered clinically. Fever clearance times were
similar. Parasite clearance was significantly faster with AMQ (mean ± SD = 1.4 ± 0.6 days, 95% confidence interval [CI] =
1.3–1.5, P < 0.0001), but polymerase chain reaction–corrected cure rates were similar (97% versus 94%). Gametocyte carriage
rates and the drug-attributable fall in hematocrit were significantly lower with AMQ (mean ± SD = 4.8 ± 3.8%, 95%
CI = 3.6–6.0, P = 0.03), but the rates of resolution of MAA were similar. Both regimens were well tolerated. AMQ clears
parasitemia and reduces gametocyte carriage more rapidly and causes lesser fall in hematocrit than MQ, but both regimens
are effective treatment of uncomplicated P. falciparum malaria in Nigerian children
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
(MAA), we use the area under curve (AUC) of anemia levels after treatment as an approach to
combine their duration and magnitude. The method involves numerical 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 (AMQ) versus mefloquine alone (MQ), and artemether-lumefantrine
(AL) versus amodiaquine-artesunate (AA) on the time-course of recovery from MAA in 109
children. Anemia resolution times were similar (10.9 ± 6.2 [SD] vs 13.3 ± 8.9 d, P = 0.2) but mean
AUC was significantly lower in AMQ- compared to MQ- treated children (35.5 ± 7.1 [SEM] vs
49.8 ± 11.3 %.h, P = 0.02) indicating larger exposure to anemia in MQ-treated children. In ALand
AA- treated children, both anemia resolution times (8.6 ± 5.3 [SD] vs 8.6 ± 4.8 d, P = 0.98)
and mean AUC (57.1 ± 12.9 [SEM] vs 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 MAA
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
Comparative Study of Biopolymer Flooding: A Core Flooding and Numerical Reservoir Simulator Validation Analysis
Polymers increase the macroscopic efficiency of the flooding process and increase crude oil recovery. The viscosity of 3 polymers
xanthan, guar, and Arabic gums is measured in the lab and experimented with as EOR options. Xanthan and guar gum polymers
are measured in weight percentages of 0.1, 0.2, 0.2, 0.4, 0.5, and 1, while gum Arabic is measured in 0.4, 0.5, 1, 5, 10, and 15 weight
percentages. The viscosity experiments showed that gum Arabic had the lowest viscosity at 15% wt. Xanthan gum and guar gum
had significantly higher viscosities than gum Arabic at corresponding weight percentages. At the same weight of 0.5%, xanthan,
guar, and Arabic gums recorded a 63%, 53%, and 46% oil recovery, respectively. Due to the limitations surrounding core flooding
experiments such as human error, equipment failure, and measurement of oil recoveries, it is necessary to validate the results
obtained with other methods such as reservoir simulation. A reservoir model is built (using Eclipse) and incorporated with
polymer and viscosity functions measured in the lab to validate results from the core flooding experiments. Peak oil recovery
of 9.96%, 9.95%, and 9.90% was recorded for xanthan, guar, and Arabic gum, respectively, at a weight percentage of 0.5%
weight. Also, increasing the wt% of injected polymers increases oil recovery. Results also indicate that the trend of oil
recoveries during core flooding follows that observed during reservoir simulation and oil production increased as percentage
weight increased for all the polymer cases considere