Does acute malnutrition in young children increase the risk of treatment failure following artemisinin-based combination therapy? A WWARN individual patient data meta-analysis

BACKGROUND

The geographical, demographic, and socioeconomic distributions of malaria and malnutrition largely overlap. It remains unknown whether malnutrition affects the efficacy of WHO-recommended artemisinin-based combination therapies (ACTs). A previous systematic review was inconclusive as data were sparse and heterogeneous, indicating that other methodological approaches, such as individual patient data meta-analysis, should be considered. The objective of this study was to conduct such a meta-analysis to assess the effect of malnutrition (wasting and stunting) on treatment outcomes in children younger than 5 years treated with an ACT for uncomplicated falciparum malaria.

METHODS

We conducted a meta-analysis of individual patient data from studies identified through a systematic review of literature published between 1980 and 2018 in PubMed, Global Health, and Cochrane Libraries (PROSPERO CRD42017056934) and inspection of the WorldWide Antimalarial Resistance Network (WWARN) repository for ACT efficacy studies, including children younger than 5 years with uncomplicated falciparum malaria. The association of either acute (wasting) or chronic (stunting) malnutrition with day 42 PCR-adjusted risk of recrudescence (ie, return of the same infection) or reinfection after therapy was investigated using Cox regression, and with day 2 parasite positivity using logistic regression.

FINDINGS

Data were included from all 36 studies targeted, 31 from Africa. Of 11 301 eligible children in 75 study sites, 11·5% were wasted (weight-for-height Z score [WHZ] <-2), and 31·8% were stunted (height-for-age Z score [HAZ] <-2). Decrease in WHZ was associated with increased risk of day 2 positivity (adjusted odds ratio 1·12, 95% CI 1·05-1·18 per unit; p=0·0002), treatment failure (adjusted hazard ratio [AHR] 1·14, 95% CI 1·02-1·26, p=0·016), and reinfection after therapy (AHR 1·09, 1·04-1·13, p=0·0003). Children with milder wasting (WHZ -2 to -1) also had a higher risk of recrudescence (AHR 1·85, 1·29-2·65, p=0·0008 vs WHZ ≥0). Stunting was not associated with reduced ACT efficacy.

INTERPRETATION

Children younger than 5 years with acute malnutrition and presenting with uncomplicated falciparum malaria were at higher risk of delayed parasite clearance, ACT treatment failure, and reinfections. Stunting was more prevalent, but not associated with changes in ACT efficacy. Acute malnutrition is known to impact medicine absorption and metabolism. Further study to inform dose optimisation of ACTs in wasted children is urgently needed.

FUNDING

Bill & Melinda Gates Foundation.

TRANSLATION

For the French translation of the abstract see Supplementary Materials section.

Safety of single-dose primaquine as a Plasmodium falciparum gametocytocide: a systematic review and meta-analysis of individual patient data

BACKGROUND

In 2012, the World Health Organization (WHO) recommended single low-dose (SLD, 0.25 mg/kg) primaquine to be added as a Plasmodium (P.) falciparum gametocytocide to artemisinin-based combination therapy (ACT) without glucose-6-phosphate dehydrogenase (G6PD) testing, to accelerate malaria elimination efforts and avoid the spread of artemisinin resistance. Uptake of this recommendation has been relatively slow primarily due to safety concerns.

METHODS

A systematic review and individual patient data (IPD) meta-analysis of single-dose (SD) primaquine studies for P. falciparum malaria were performed. Absolute and fractional changes in haemoglobin concentration within a week and adverse effects within 28 days of treatment initiation were characterised and compared between primaquine and no primaquine arms using random intercept models.

RESULTS

Data comprised 20 studies that enrolled 6406 participants, of whom 5129 (80.1%) had received a single target dose of primaquine ranging between 0.0625 and 0.75 mg/kg. There was no effect of primaquine in G6PD-normal participants on haemoglobin concentrations. However, among 194 G6PD-deficient African participants, a 0.25 mg/kg primaquine target dose resulted in an additional 0.53 g/dL (95% CI 0.17-0.89) reduction in haemoglobin concentration by day 7, with a 0.27 (95% CI 0.19-0.34) g/dL haemoglobin drop estimated for every 0.1 mg/kg increase in primaquine dose. Baseline haemoglobin, young age, and hyperparasitaemia were the main determinants of becoming anaemic (Hb < 10 g/dL), with the nadir observed on ACT day 2 or 3, regardless of G6PD status and exposure to primaquine. Time to recovery from anaemia took longer in young children and those with baseline anaemia or hyperparasitaemia. Serious adverse haematological events after primaquine were few (9/3, 113, 0.3%) and transitory. One blood transfusion was reported in the primaquine arms, and there were no primaquine-related deaths. In controlled studies, the proportions with either haematological or any serious adverse event were similar between primaquine and no primaquine arms.

CONCLUSIONS

Our results support the WHO recommendation to use 0.25 mg/kg of primaquine as a P. falciparum gametocytocide, including in G6PD-deficient individuals. Although primaquine is associated with a transient reduction in haemoglobin levels in G6PD-deficient individuals, haemoglobin levels at clinical presentation are the major determinants of anaemia in these patients.

TRIAL REGISTRATION

PROSPERO, CRD42019128185.

Haematological consequences of acute uncomplicated falciparum malaria: a WorldWide Antimalarial Resistance Network pooled analysis of individual patient data

BACKGROUND

Plasmodium falciparum malaria is associated with anaemia-related morbidity, attributable to host, parasite and drug factors. We quantified the haematological response following treatment of uncomplicated P. falciparum malaria to identify the factors associated with malarial anaemia.

METHODS

Individual patient data from eligible antimalarial efficacy studies of uncomplicated P. falciparum malaria, available through the WorldWide Antimalarial Resistance Network data repository prior to August 2015, were pooled using standardised methodology. The haematological response over time was quantified using a multivariable linear mixed effects model with nonlinear terms for time, and the model was then used to estimate the mean haemoglobin at day of nadir and day 7. Multivariable logistic regression quantified risk factors for moderately severe anaemia (haemoglobin < 7 g/dL) at day 0, day 3 and day 7 as well as a fractional fall ≥ 25% at day 3 and day 7.

RESULTS

A total of 70,226 patients, recruited into 200 studies between 1991 and 2013, were included in the analysis: 50,859 (72.4%) enrolled in Africa, 18,451 (26.3%) in Asia and 916 (1.3%) in South America. The median haemoglobin concentration at presentation was 9.9 g/dL (range 5.0-19.7 g/dL) in Africa, 11.6 g/dL (range 5.0-20.0 g/dL) in Asia and 12.3 g/dL (range 6.9-17.9 g/dL) in South America. Moderately severe anaemia (Hb < 7g/dl) was present in 8.4% (4284/50,859) of patients from Africa, 3.3% (606/18,451) from Asia and 0.1% (1/916) from South America. The nadir haemoglobin occurred on day 2 post treatment with a mean fall from baseline of 0.57 g/dL in Africa and 1.13 g/dL in Asia. Independent risk factors for moderately severe anaemia on day 7, in both Africa and Asia, included moderately severe anaemia at baseline (adjusted odds ratio (AOR) = 16.10 and AOR = 23.00, respectively), young age (age < 1 compared to ≥ 12 years AOR = 12.81 and AOR = 6.79, respectively), high parasitaemia (AOR = 1.78 and AOR = 1.58, respectively) and delayed parasite clearance (AOR = 2.44 and AOR = 2.59, respectively). In Asia, patients treated with an artemisinin-based regimen were at significantly greater risk of moderately severe anaemia on day 7 compared to those treated with a non-artemisinin-based regimen (AOR = 2.06 [95%CI 1.39-3.05], p < 0.001).

CONCLUSIONS

In patients with uncomplicated P. falciparum malaria, the nadir haemoglobin occurs 2 days after starting treatment. Although artemisinin-based treatments increase the rate of parasite clearance, in Asia they are associated with a greater risk of anaemia during recovery.

Can Deep Synthesis of EMG Overcome the Geometric Growth of Training Data Required to Recognize Multiarticulate Motions?. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021;2021:6380-6383. [PMID: 34892572 DOI: 10.1109/embc46164.2021.9630276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

By being predicated on supervised machine learning, pattern recognition approaches to myoelectric prosthesis control require electromyography (EMG) training data collected concurrently with every detectable motion. Within this framework, calibration protocols for simultaneous control of multifunctional prosthetic hands rapidly become prohibitively long-the number of unique motions grows geometrically with the number of controllable degrees of freedom (DoFs). This paper proposes a technique intended to circumvent this combinatorial explosion. Using EMG windows from 1-DoF motions as input and EMG windows from 2-DoF motions as targets, we train generative deep learning models to synthesize EMG windows appertaining to multi-DoF motions. Once trained, such models can be used to complete datasets consisting of only 1-DoF motions, enabling simple calibration protocols with durations that scale linearly with the number of DoFs. We evaluated synthetic EMG produced in this way via a classification task using a database of forearm surface EMG collected during 1-DoF and 2-DoF motions. Multi-output classifiers were trained on either (I) real data from 1-DoF and 2-DoF motions, (II) real data from only 1-DoF motions, or (III) real data from 1-DoF motions appended with synthetic EMG from 2-DoF motions. When tested on data containing all possible motions, classifiers trained on synthetic-appended data (III) significantly outperformed classifiers trained on 1-DoF real data (II), although significantly underperformed classifiers trained on both 1- and 2-DoF real data (I) (I < 0.05). These findings suggest that it is feasible to model EMG concurrent with multiarticulate motions as nonlinear combinations of EMG from constituent 1-DoF motions, and that such modelling can be harnessed to synthesize realistic training data.

Efficacy of Single-Dose Primaquine With Artemisinin Combination Therapy on Plasmodium falciparum Gametocytes and Transmission: An Individual Patient Meta-Analysis

BACKGROUND

Since the World Health Organization recommended single low-dose (0.25 mg/kg) primaquine (PQ) in combination with artemisinin-based combination therapies (ACTs) in areas of low transmission or artemisinin-resistant Plasmodium falciparum, several single-site studies have been conducted to assess efficacy.

METHODS

An individual patient meta-analysis to assess gametocytocidal and transmission-blocking efficacy of PQ in combination with different ACTs was conducted. Random effects logistic regression was used to quantify PQ effect on (1) gametocyte carriage in the first 2 weeks post treatment; and (2) the probability of infecting at least 1 mosquito or of a mosquito becoming infected.

RESULTS

In 2574 participants from 14 studies, PQ reduced PCR-determined gametocyte carriage on days 7 and 14, most apparently in patients presenting with gametocytemia on day 0 (odds ratio [OR], 0.22; 95% confidence interval [CI], .17-.28 and OR, 0.12; 95% CI, .08-.16, respectively). Rate of decline in gametocyte carriage was faster when PQ was combined with artemether-lumefantrine (AL) compared to dihydroartemisinin-piperaquine (DP) (P = .010 for day 7). Addition of 0.25 mg/kg PQ was associated with near complete prevention of transmission to mosquitoes.

CONCLUSIONS

Transmission blocking is achieved with 0.25 mg/kg PQ. Gametocyte persistence and infectivity are lower when PQ is combined with AL compared to DP.

Exploiting the Intertemporal Structure of the Upper-Limb sEMG: Comparisons between an LSTM Network and Cross-Sectional Myoelectric Pattern Recognition Methods

The use of natural myoelectric interfaces promises great value for a variety of potential applications, clinical and otherwise, provided a computational mapping between measured neuromuscular activity and executed motion can be approximated to a satisfactory degree. However, prevalent methods intended for such decoding of movement intent from the surface electromyogram (sEMG) based on pattern recognition typically do not capitalize on the inherently time series-like nature of the acquired signals. In this paper, we present the results from a comparative study in which the performances of traditional cross-sectional pattern recognition methods were compared with that of a classifier built on the natural assumption of temporal ordering by utilizing a long short-term memory (LSTM) neural network. The resulting evaluation indicate that the LSTM approach outperforms traditional gesture recognition techniques which are based on cross-sectional inference. These findings held both when the LSTM classifier operated on conventional features and on raw sEMG and for both healthy subjects and transradial amputees.

Falciparum malaria from coastal Tanzania and Zanzibar remains highly connected despite effective control efforts on the archipelago

BACKGROUND

Tanzania's Zanzibar archipelago has made significant gains in malaria control over the last decade and is a target for malaria elimination. Despite consistent implementation of effective tools since 2002, elimination has not been achieved. Importation of parasites from outside of the archipelago is thought to be an important cause of malaria's persistence, but this paradigm has not been studied using modern genetic tools.

METHODS

Whole-genome sequencing (WGS) was used to investigate the impact of importation, employing population genetic analyses of Plasmodium falciparum isolates from both the archipelago and mainland Tanzania. Ancestry, levels of genetic diversity and differentiation, patterns of relatedness, and patterns of selection between these two populations were assessed by leveraging recent advances in deconvolution of genomes from polyclonal malaria infections.

RESULTS

Significant decreases in the effective population sizes were inferred in both populations that coincide with a period of decreasing malaria transmission in Tanzania. Identity by descent analysis showed that parasites in the two populations shared long segments of their genomes, on the order of 5 cM, suggesting shared ancestry within the last 10 generations. Even with limited sampling, two of isolates between the mainland and Zanzibar were identified that are related at the expected level of half-siblings, consistent with recent importation.

CONCLUSIONS

These findings suggest that importation plays an important role for malaria incidence on Zanzibar and demonstrate the value of genomic approaches for identifying corridors of parasite movement to the island.

Safety and efficacy of re-treatments with pyronaridine-artesunate in African patients with malaria: a substudy of the WANECAM randomised trial

BACKGROUND

Sparse data on the safety of pyronaridine-artesunate after repeated treatment of malaria episodes restrict its clinical use. We therefore compared the safety of pyronaridine-artesunate after treatment of the first episode of malaria versus re-treatment in a substudy analysis.

METHODS

This planned substudy analysis of the randomised, open-label West African Network for Clinical Trials of Antimalarial Drugs (WANECAM) phase 3b/4 trial was done at six health facilities in Mali, Burkina Faso, and Guinea in patients (aged ≥6 months and bodyweight ≥5 kg) with uncomplicated microscopically confirmed Plasmodium spp malaria (parasite density <200 000 per μL blood) and fever or history of fever. The primary safety endpoint was incidence of hepatotoxicity: alanine aminotransferase of greater than five times the upper limit of normal (ULN) or Hy's criteria (alanine aminotransferase or aspartate aminotransferase greater than three times the ULN and total bilirubin more than twice the ULN) after treatment of the first episode of malaria and re-treatment (≥28 days after first treatment) with pyronaridine-artesunate. Pyronaridine-artesunate efficacy was compared with artemether-lumefantrine with the adequate clinical and parasitological response (ACPR) in an intention-to-treat analysis. WANECAM is registered with PACTR.org, number PACTR201105000286876.

FINDINGS

Following first treatment, 13 (1%) of 996 patients had hepatotoxicity (including one [<1%] possible Hy's law case) versus two (1%) of 311 patients on re-treatment (neither a Hy's law case). No evidence was found that pyronaridine-artesunate re-treatment increased safety risk based on laboratory values, reported adverse event frequencies, or electrocardiograph findings. For all first treatment or re-treatment episodes, pyronaridine-artesunate (n=673) day 28 crude ACPR was 92·7% (95% CI 91·0-94·3) versus 80·4% (77·8-83·0) for artemether-lumefantrine (n=671). After exclusion of patients with PCR-confirmed new infections, ACPR was similar on treatment and re-treatment and greater than 95% at day 28 and greater than 91% at day 42 in both treatment groups.

INTERPRETATION

The findings that pyronaridine-artesunate safety and efficacy were similar on first malaria treatment versus re-treatment of subsequent episodes lend support for the wider access to pyronaridine-artesunate as an alternative artemisinin-based combination treatment for malaria in sub-Saharan Africa.

FUNDING

European and Developing Countries Clinical Trial Partnership, Medicines for Malaria Venture (Geneva, Switzerland), UK Medical Research Council, Swedish International Development Cooperation Agency, German Ministry for Education and Research, University Claude Bernard (Lyon, France), Malaria Research and Training Centre (Bamako, Mali), Centre National de Recherche et de Formation sur le Paludisme (Burkina Faso), Institut de Recherche en Sciences de la Santé (Bobo-Dioulasso, Burkina Faso), and Centre National de Formation et de Recherche en Santé Rurale (Republic of Guinea).

Polymorphisms in the K13-propeller gene in artemisinin-susceptible Plasmodium falciparum parasites from Bougoula-Hameau and Bandiagara, Mali

Artemisinin-resistant Plasmodium falciparum malaria has been documented in southeast Asia and may already be spreading in that region. Molecular markers are important tools for monitoring the spread of antimalarial drug resistance. Recently, single-nucleotide polymorphisms (SNPs) in the PF3D7_1343700 kelch propeller (K13-propeller) domain were shown to be associated with artemisinin resistance in vivo and in vitro. The prevalence and role of K13-propeller mutations are poorly known in sub-Saharan Africa. K13-propeller mutations were genotyped by direct sequencing of nested polymerase chain reaction (PCR) amplicons from dried blood spots of pre-treatment falciparum malaria infections collected before and after the use of artemisinin-based combination therapy (ACT) as first-line therapy in Mali. Although K13-propeller mutations previously associated with delayed parasite clearance in Cambodia were not identified, 26 K13-propeller mutations were identified in both recent samples and pre-ACT infections. Parasite clearance time was comparable between infections with non-synonymous K13-propeller mutations and infections with the reference allele. These findings suggest that K13-propeller mutations are present in artemisinin-sensitive parasites and that they preceded the wide use of ACTs in Mali.

Diagnostic performance of radiographs and computed tomography for displacement and instability of acute scaphoid waist fractures

BACKGROUND

Fracture displacement is the most important factor associated with nonunion of a scaphoid waist fracture.We evaluated the performance characteristics of radiographs and computed tomography (CT) in the diagnosis of intraoperative displacement and instability of scaphoid waist fractures using wrist arthroscopy as the reference standard.

METHODS

During a six-year period (2004 to 2010) at two institutions, forty-four adult patients with a scaphoid waist fracture underwent arthroscopy-assisted operative fracture treatment at a mean of nine days (range, two to twenty-two days) after injury. Subjects included all of those with a displaced scaphoid fracture seen on radiographs and a selection of patients with a nondisplaced scaphoid fracture. All patients had preoperative radiographs and CT. Arthroscopy with up to 5 kg of traction was the reference standard for fracture displacement and instability.

RESULTS

The reference standard (arthroscopy) led to a diagnosis of twenty-two displaced fractures (all unstable) and twenty-two nondisplaced fractures (seven unstable). Displacement was diagnosed in eleven patients (25%) with the use of radiographs and in twenty (45%) with CT. The sensitivity, specificity, and accuracy for diagnosing intraoperative displacement were 45%, 95%, and 70%, respectively, with the use of radiographs and 77%, 86%, and 82%, respectively, with CT. The sensitivity, specificity, and accuracy for diagnosing intraoperative instability were 34%, 93%, and 55%, respectively,with the use of radiographs and 62%, 87%, and 70%, respectively, with CT. Assuming a 10% prevalence of fracture displacement and instability among all scaphoid waist fractures, the positive and negative predictive values for displacement were 53% and 94%, respectively, with the use of radiographs and 39% and 97% with CT whereas the positive and negative predictive values for instability were 36% and 93%, respectively, with radiographs and 34% and 95% with CT.

CONCLUSIONS

Radiographs and CT scans cannot be relied on to accurately diagnose intraoperative scaphoid fracture displacement or instability compared with arthroscopic examination. The influence, with regard to the risk of nonunion, of intraoperative instability of a scaphoid fracture that is seen to be nondisplaced on radiographs or CT is currently unknown.

LEVEL OF EVIDENCE

Diagnostic Level III.

Cytochrome 1A1 and 1B1 gene diversity in the Zanzibar islands

Amodiaquine (AQ) is a 4-aminoquinoline widely used in the treatment of malaria as part of the artemisinin combination therapy (ACT). AQ is metabolised towards its main metabolite desethylamodiaquine mainly by cytochrome P450 2C8 (CYP2C8). CYP1A1 and CYP1B1 play a minor role in the metabolism but they seem to be significantly involved in the formation of the short-lived quinine-imine. To complete the genetic variation picture of the main genes involved in AQ metabolism in the Zanzibar population, previously characterised for CYP2C8, we analysed in this study CYP1A1 and CYP1B1 main genetic polymorphisms. The results obtained show a low frequency of the CYP1A1*2B/C allele (2.4%) and a high frequency of CYP1B1*6 (approximately 42%) followed by CYP1B1*2 (approximately 27%) in Zanzibar islands. Genotype data for CYP1A1 and CYP1B1 show a low incidence of fast metabolisers, revealing a relatively safe genetic background in Zanzibar's population regarding the appearance of adverse effects.

Drug resistance associated genetic polymorphisms in Plasmodium falciparum and Plasmodium vivax collected in Honduras, Central America

Background

In Honduras, chloroquine and primaquine are recommended and still appear to be effective for treatment of Plasmodium falciparum and Plasmodium vivax malaria. The aim of this study was to determine the proportion of resistance associated genetic polymorphisms in P. falciparum and P. vivax collected in Honduras.

Methods

Blood samples were collected from patients seeking medical attention at the Hospital Escuela in Tegucigalpa from 2004 to 2006 as well as three regional hospitals, two health centres and one regional laboratory during 2009. Single nucleotide polymorphisms in P. falciparum chloroquine resistance transporter (pfcrt), multidrug resistance 1 (pfmdr1), dihydrofolate reductase (pfdhfr) and dihydropteroate synthase (pfdhps) genes and in P. vivax multidrug resistance 1 (pvmdr1) and dihydrofolate reductase (pvdhfr) genes were detected using PCR based methods.

Results

Thirty seven P. falciparum and 64 P. vivax samples were collected. All P. falciparum infections acquired in Honduras carried pfcrt, pfmdr1, pfdhps and pfdhfr alleles associated with chloroquine, amodiaquine and sulphadoxine-pyrimethamine sensitivity only. One patient with parasites acquired on a Pacific Island had pfcrt 76 T and pfmdr1 86Y alleles. That patient and a patient infected in West Africa had pfdhfr 51I, 59 R and 108 N alleles. Pvmdr1 976 F was found in 7/37 and two copies of pvmdr1 were found in 1/37 samples. Pvdhfr 57 L + 58 R was observed in 2/57 samples.

Conclusion

The results indicate that P. falciparum from Honduras remain sensitive to chloroquine and sulphadoxine-pyrimethamine. This suggests that chloroquine and sulphadoxine-pyrimethamine should be efficacious for treatment of uncomplicated P. falciparum malaria, supporting current national treatment guidelines. However, genetic polymorphisms associated with chloroquine and sulphadoxine-pyrimethamine tolerance were detected in local P. vivax and imported P. falciparum infections. Continuous monitoring of the prevalence of drug resistant/tolerant P. falciparum and P. vivax is therefore essential also in Honduras.

Reductions in malaria and anaemia case and death burden at hospitals following scale-up of malaria control in Zanzibar, 1999-2008

Background

In Zanzibar, the Ministry of Health and partners accelerated malaria control from September 2003 onwards. The impact of the scale-up of insecticide-treated nets (ITN), indoor-residual spraying (IRS) and artemisinin-combination therapy (ACT) combined on malaria burden was assessed at six out of seven in-patient health facilities.

Methods

Numbers of outpatient and inpatient cases and deaths were compared between 2008 and the pre-intervention period 1999-2003. Reductions were estimated by segmented log-linear regression, adjusting the effect size for time trends during the pre-intervention period.

Results

In 2008, for all age groups combined, malaria deaths had fallen by an estimated 90% (95% confidence interval 55-98%)(p < 0.025), malaria in-patient cases by 78% (48-90%), and parasitologically-confirmed malaria out-patient cases by 99.5% (92-99.9%). Anaemia in-patient cases decreased by 87% (57-96%); anaemia deaths and out-patient cases declined without reaching statistical significance due to small numbers. Reductions were similar for children under-five and older ages. Among under-fives, the proportion of all-cause deaths due to malaria fell from 46% in 1999-2003 to 12% in 2008 (p < 0.01) and that for anaemia from 26% to 4% (p < 0.01). Cases and deaths due to other causes fluctuated or increased over 1999-2008, without consistent difference in the trend before and after 2003.

Conclusions

Scaling-up effective malaria interventions reduced malaria-related burden at health facilities by over 75% within 5 years. In high-malaria settings, intensified malaria control can substantially contribute to reaching the Millennium Development Goal 4 target of reducing under-five mortality by two-thirds between 1990 and 2015.

Impact of training in clinical and microscopy diagnosis of childhood malaria on antimalarial drug prescription and health outcome at primary health care level in Tanzania: a randomized controlled trial

BACKGROUND

Prescribing antimalarial medicines based on parasite confirmed diagnosis of malaria is critical to rational drug use and optimal outcome of febrile illness. The impact of microscopy-based versus clinical-based diagnosis of childhood malaria was assessed at primary health care (PHC) facilities using a cluster randomized controlled training intervention trial.

METHODS

Sixteen PHC facilities in rural Tanzania were randomly allocated to training of health staff in clinical algorithm plus microscopy (Arm-I, n = 5) or clinical algorithm only (Arm-II, n = 5) or no training (Arm-III, n = 6). Febrile under-five children presenting at these facilities were assessed, treated and scheduled for follow up visit after 7 days. Blood smears on day 0 were only done in Arm-I but on Day 7 in all arms. Primary outcome was antimalarial drug prescription. Other outcomes included antibiotic prescription and health outcome. Multilevel regression models were applied with PHC as level of clustering to compare outcomes in the three study arms.

RESULTS

A total of 973, 1,058 and 1,100 children were enrolled in arms I, II and III, respectively, during the study period. Antimalarial prescriptions were significantly reduced in Arm-I (61.3%) compared to Arms-II (95.3%) and III (99.5%) (both P < 0.001), whereas antibiotic prescriptions did not vary significantly between the arms (49.9%, 54.8% and 34.2%, respectively). In Arm-I, 99.1% of children with positive blood smear readings received antimalarial prescriptions and so did 11.3% of children with negative readings. Those with positive readings were less likely to be prescribed antibiotics than those with negative (relative risk = 0.66, 95% confidence interval: 0.55, 0.72). On day 7 follow-up, more children reported symptoms in Arm-I compared to Arm-III, but fewer children had malaria parasitaemia (p = 0.049). The overall sensitivity of microscopy reading at PHC compared to reference level was 74.5% and the specificity was 59.0% but both varied widely between PHCs.

CONCLUSION

Microscopy based diagnosis of malaria at PHC facilities reduces prescription of antimalarial drugs, and appears to improve appropriate management of non-malaria fevers, but major variation in accuracy of the microscopy readings was found. Lack of qualified laboratory technicians at PHC facilities and the relatively short training period may have contributed to the shortcomings.

TRIAL REGISTRATION

This study is registered at Clinicaltrials.gov with the identifier NCT00687895.

Variability in malaria prophylaxis prescribing across Europe: a Delphi method analysis

BACKGROUND

The indications for prescribing malaria chemoprophylaxis lack a solid evidence base that results in subjectivity and wide variation of practice across countries and among professionals.

METHODS

European experts in travel medicine, who are members of TropNetEurop, participated in a survey conducted using the Delphi method. This technique aims at evaluating and developing a consensus through iterations of questionnaires, controlled feedback, and statistical group responses.

RESULTS

A first questionnaire, including questions about controversial issues in prescribing malaria prophylaxis, required responses on a visual scale between 1 and 10. The questionnaire included issues on problematic prescribing, characteristics of drugs, relevance of geography, and importance of insect bite prevention. The repeat questionnaire with the group response from the first round revealed an increasing consensus on most issues. A second survey considered 14 practical scenarios (including two internal standards) and investigated preferred choice of prophylaxis. A significant consensus was noted in 8 of 14 scenarios, which did not increase after a second round. The analysis revealed a wide variation in prescribing choices with preferences grouped by region of practice, and a greater willingness to prescribe in northern and southern Europe than in central Europe. The second round showed a 9.5% change of opinion.

CONCLUSIONS

The study shows that improving the evidence base on efficacy and tolerability and risk of malaria for prescribing chemoprophylaxis is needed as is further discussion across Europe to achieve harmonization of prescribing practice.

Effect of artesunate plus sulfadoxine-pyrimethamine on haematological recovery and anaemia, in Kenyan children with uncomplicated, Plasmodium falciparum malaria

Malaria-associated anaemia is a major public-health problem. Although the treatment of uncomplicated, Plasmodium falciparum malaria aims to clear the parasites, relieve the symptoms and permit haematological recovery, data on the impact of antimalarial treatment on haematological recovery are few. Haematological recovery and the prevalence of anaemia were therefore evaluated in 600 Kenyan children with uncomplicated malaria who were randomly assigned to one of three treatment groups. The children were given sulfadoxine-pyrimethamine (SP) on day 0, SP plus artesunate on day 0 (AS1), or SP on day 0 and artesunate on each of days 0-2 (AS3). Haemoglobin (Hb) concentrations were measured on days 0, 7, 14, 21 and 28, with haematological recovery defined as a day-28 Hb concentration of at least 11 g/dl. Only 96 (18%) of the 543 children who were anaemic (i.e. with <11.0 g Hb/dl) at enrolment achieved haematological recovery. The prevalence of anaemia fell from 91% on day 0 to 74% (252/340) by day 28 (P=0.065). Compared with SP alone, neither artesunate regimen resulted in higher Hb concentrations on day 28 (with means of 10.2, 9.9 and 10.2 g/dl for AS3, AS1 and SP, respectively; P=0.254), a higher frequency of haematological recovery (19%, 14% and 20% for AS3, AS1 and SP, respectively; P=0.301) or a greater reduction in the prevalence of anaemia (prevalences in the AS3, AS1 and SP arms falling from 90%, 89% and 93%, respectively, on day 0, to corresponding values of 71%, 82% and 69% on day 28; P=0.40). In fact, between days 0 and 7, the children in the AS3 arm showed a larger drop in mean Hb than the children in the other two treatment arms. In general, haematological recovery was most likely in older children who had mild anaemia at presentation and were parasitologically cured. Overall, the frequencies of haematological recovery were modest and not influenced by the artesunate treatments. Other factors contributing to anaemia need to be explored more fully.

Influence of consecutive-day blood sampling on polymerase chain reaction-adjusted parasitological cure rates in an antimalarial-drug trial conducted in Tanzania

We assessed the influence that consecutive-day blood sampling, compared with single-day blood sampling, had on polymerase chain reaction (PCR)-adjusted parasitological cure after stepwise genotyping of merozoite surface proteins 2 (msp2) and 1 (msp1) in 106 children in Tanzania who had uncomplicated falciparum malaria treated with either sulfadoxine-pyrimethamine or artemether-lumefantrine; 78 of these children developed recurrent parasitemia during the 42-day follow-up period. Initial msp2 genotyping identified 27 and 33 recrudescences by use of single- and consecutive-day sampling, respectively; in subsequent msp1 genotyping, 17 and 21 of these episodes, respectively, were still classified as recrudescences; these results indicate a similar sensitivity of the standard single-day PCR protocol--that is, 82% (27/33) and 81% (17/21), in both genotyping steps. Interpretation of PCR-adjusted results will significantly depend on methodology.

Algorithm for the diagnosis of anaemia without laboratory facilities among small children in a malaria endemic area of rural Tanzania

BACKGROUND

Anaemia among small children in tropical Africa is common and often caused by infection with Plasmodium falciparum. The diagnosis of anaemia is difficult without a laboratory estimation of haemoglobin. The aim of this study was to examine if clinical findings related to malaria and anaemia would help to detect moderate and/or severe anaemia in children in rural Tanzania.

METHODS

Children between 6 and 36 months were examined by health workers in an Out Patient Department (OPD) to detect severe anaemia (packed cell volume, PCV< or =20%) and in a cross sectional survey at village level to identify moderate anaemia (PCV 21-25%). History of recent fever and treatments was recorded and a clinical examination was performed.

FINDINGS

In the survey, comparison of 65 moderately anaemic children with 373 mild/non anaemic children revealed no differences in history of fever or in the clinical examination. In the OPD comparison of 100 severely anaemic children with 116 non-severely anaemic control children revealed that pallor, respiratory rate, number of fever days last week, deteriorated general condition, heart rate, age, splenomegaly, low body weight and elevated body temperature were all indicators of severe 'anaemia, only pallor, respiratory rate, fever days and palpable spleen however, remained associated with severe anaemia in multiple regression analysis. The combination of any pallor and either respiratory rate >55/min or fever >3 days, could predict severe anaemia with a sensitivity of 96% and a specificity of 71%. This was better than the currently recommended signs of severe pallor or an approximation of the Integrated Management of Childhood Illness (IMCI) criteria's for referral of children.

INTERPRETATION

At primary health care level detection of severe anaemia can be improved by information about fever duration and determination of respiratory rate in children with pallor.

Pallor as a sign of anaemia in small Tanzanian children at different health care levels

BACKGROUND

Anaemia is a major complication of Plasmodium falciparum malaria among small children in sub-Saharan Africa. We studied the performance of the Integrated Management of Childhood Illness (IMCI) recommended assessment of no/some/severe pallor as predictor of anaemia in health surveys at community level and in clinical practice in an out patient department (OPD) and in a hospital ward in rural Tanzania.

METHODS

The study was undertaken among 6-36 months old children. Pallor was evaluated as a combined assessment of conjunctiva, tongue and palms and categorised as no, some or severe pallor. Packed cell volume (PCV) was measured and related to pallor.

FINDINGS

A total of 740 examinations were performed at village, OPD and in the hospital ward. The prevalences of severe pallor were 0%, 1.5% and 7% respectively. The prevalences of any pallor were 14%, 41% and 86%. The prevalences of severe anaemia (PCV<21%) were 1%, 5% and 81% and of any anaemia (PCV<33%) 68%, 73% and 98%. Severe pallor could not detect severe anaemia. The sensitivities were only 0%, 0% and 8%. The sensitivities of any pallor to detect severe anaemia were however 86% and 98% for children at the health care facility level, but still of relatively poor predictive values since the specificities were only 61% and 68%.

INTERPRETATION

Division of pallor into some or severe degrees was of no use at any health care level. The identification of any pallor was of no use at village level, but it may possibly be of some value as a screening test for severe anaemia at health care facilities, if additional assessment is included in view of the low specificity and positive predictive value of the finding.

CYP2C8 polymorphism frequencies among malaria patients in Zanzibar

OBJECTIVE

The determination of the prevalence of the CYP2C8 main alleles in a typical set of malaria patients in Zanzibar, as these patients represent a typical population exposed to amodiaquine, an antimalarial mainly metabolized by CYP2C8. Also, to determine for the first time the frequencies of CYP2C8 alleles in native African populations.

METHODS

Polymerase chain reaction-restriction fragment polymorphism for the identification of CYP2C8*1, CYP2C8*2, CYP2C8*3 and CYP2C8*4 on a random population of 165 unrelated malaria patients.

RESULTS

The allele frequencies found were: CYP2C8*1 (wild type, 83.4%), CYP2C8*2 (13.9%), CYP2C8*3 (2.1%) and CYP2C8*4 (0.6%). In terms of genotypes, 70.4% of the patients showed the CYP2C8*1/ CYP2C8*1 genotypes, while heterozygous between the wild type and other minor alleles were seen in 26.0%. Finally, 3.6% of the patients were homozygous for slow metabolizer alleles. The frequencies observed are equivalent to those documented for African-Americans.

CONCLUSIONS

CYP2C8 non-wild type alleles have a significant prevalence in the East African population studied. The consequent frequency of 3.6% of patients homozygous for slow metabolizer alleles represent a significant fraction of the population potentially in higher risk of adverse effects due to a less efficient metabolism of amodiaquine. As approximately 10(6) first-line treatments are currently performed in Zanzibar per year, this represents a non-negligible absolute number of amodiaquine exposures. This information constitutes a background for the pharmacovigilance programs presently being employed in Zanzibar.

Acute haemolysis in childhood falciparum malaria

Acute haemolysis associated with clinical episodes of high-level Plasmodium falciparum parasitaemia was studied in 20 children from an holoendemic area (coastal Tanzania). The change in blood haemoglobin (Hb) concentration ranged from -46 to g/L during the 72-h observation period and was linearly related to maximum parasitaemia. Balance studies between loss of blood Hb, increase in plasma Hb and appearance of Hb in the urine indicated that extravascular clearance of red cells was the predominant mode of erythrocyte clearance. Most subjects, however, showed minor signs of intravascular haemolysis. The plasma Hb was << 1% of blood Hb and haemoglobinuria was detected in 14/20 children but the excretion of Hb in urine was < 0.5% of total Hb loss. Haemoglobinuria was, however, a marker of severe haemolysis, since the maximum blood Hb loss in children without haemoglobinuria was 10 g/L. Erythrocyte-bound opsonins known to induce erythrophagocytosis, i.e., complement C3c fragments and autologous IgG, were increased in all patients. In the patients with major haemolysis, the changes correlated to the haemolysis over time. Hence, a similar mechanism for predominantly extravascular erythrocyte clearance may be operative in acute malarial anaemia, normal erythrocyte senescence and other forms of acute haemolysis.

Hemoglobin concentration in children in a malaria holoendemic area is determined by cumulated Plasmodium falciparum parasite densities

In malaria holoendemic areas children are anemic, but the exact influence of falciparum malaria on hemoglobin (Hb) concentration remains largely unsettled. Prospective data were therefore collected in children < 24 months of age during five months in a Tanzanian village. Children with mean asymptomatic parasitemia > or = 400/microl had lower median Hb levels during the study than those with mean density < 400/microl. The difference was 9.7 g/L (95% confidence interval [CI] 2.8-17). In children with one or more clinical malaria episodes, the median Hb was 8.3 g/L (95% CI 0.9-16) lower than those without episode. If early treatment failure was recorded, the immediate effect on Hb was particularly important with a mean drop of 17 g/L. Interestingly, at study-end the Hb concentration represented a function of the area under the parasitemia curve (AUPC) during the previous five months, adjusting for age. In conclusion, stepwise deterioration in median Hb levels was found by asymptomatic parasitemia, clinical malaria episode, and most significantly, treatment failure.

Comparison of rectal artemisinin with intravenous quinine in the treatment of severe malaria in Ethiopia

OBJECTIVE

To compare the clinical efficacy and safety of artemisinin suppository with quinine injection.

DESIGN

Comparative open randomised study.

SETTING

A government regional referral hospital in Ethiopia.

SUBJECTS

Sixty five adult patients of both sexes: 32 for artemisinin and 33 for quinine with complicated severe falciparum malaria.

MAIN OUTCOME MEASURES

Therapeutic responses and adverse reactions.

RESULTS

The clinical and laboratory data in both groups of patients on admission were comparable. The parasite clearance time (PCT), fever subsidence time (FST) and coma resolution time (CRT) were shorter in the artemisinin treated group. There was no significant different in the parasitological cure rates in both arms of treatment. No correlation was observed between the initial parasite density and PCT or FST in both groups of treatment. Mortality rates were similar both in the artemisinin and quinine groups. The common adverse effects observed in most patients receiving quinine, in an increasing order of occurrence were; vomiting, dizziness, hypoglycaemia and tinnitus, which were all relatively rare with artemisinin. Some patients treated with artemisinin showed tenesmus which was not observed in any patient treated with quinine.

CONCLUSION

The rectal artemisinin is more efficacious and safer than the intravenous quinine. Thus, artemisinin may be considered a potential drug which can replace quinine in the treatment of severe malaria in Ethiopia provided it is made available at affordable prices.

Screening for human T cell leukaemia/lymphoma virus among blood donors in Sweden: cost effectiveness analysis

OBJECTIVE

To analyse the cost effectiveness of a national programme to screen blood donors for infection with the human T cell leukaemia/lymphoma virus.

DESIGN

Three models for calculating the costs and benefits of screening were developed. The first model analysed the cost of continuously testing all donations; the second analysed the cost of initially testing new blood donors and then retesting them after five years; the third analysed the cost of testing donors only at the time of their first donation. Patients who had received blood components from donors confirmed to be infected with the virus were offered testing.

SETTING

Sweden.

MAIN OUTCOME MEASURES

Prevalence of infection with the virus among blood donors, the risk of transmission of the virus, screening costs, and the outcome of infection.

RESULTS

648 497 donations were tested for the virus; 1625 samples tested positive by enzyme linked immunosorbent assay. 6 were confirmed positive by western blotting. The prevalence of infection with the virus was 2/100 000 donors. 35 patients who had received blood infected with the virus were tested; 3 were positive. The cost of testing every donation was calculated to be $3.02m (1.88m pounds); this is 18 times higher than the cost of testing new donors only, and only 1 additional positive donor would be discovered in 7 years. Regardless of the model used, screening was estimated to prevent only 1 death every 200 years at a minimum cost of $36m (22.5m pounds).

CONCLUSION

Based on these estimates the Swedish National Board of Health and Welfare decided that only new blood donors would be screened for infection with the virus.

Daily dynamics of Plasmodium falciparum subpopulations in asymptomatic children in a holoendemic area

Plasmodium falciparum is the major cause of malaria morbidity and mortality in the world. Biologic and antigenic diversity is a characteristic of this parasite and infections can consist of several genetically diverse parasites. The daily dynamics of these parasite subpopulations were investigated in asymptomatic children in rural Tanzania. Fingerprick blood samples were collected on 14 consecutive days from 20 children. Parasite densities were detected by light microscopy and genotyping of P. falciparum was done using a nested polymerase chain reaction (PCR) assay targeting polymorphic regions on the merozoite surface protein-1 (MSP-1), MSP-2, and glutamine-rich protein (GLURP) genes. In the eight children harboring P. falciparum throughout the study period, infections were found to be highly complex with daily changes in both parasite density and genotypic pattern. A nonrandom. 48-hr periodicity in these fluctuations suggests that P. falciparum infections consist of inherently synchronous subpopulations of parasites. These findings have important biologic and epidemiologic implications since one blood sample may only partly reflect the whole parasite population in an infected individual.

Efficacy of oral and intravenous artesunate in male Tanzanian adults with Plasmodium falciparum malaria and in vitro susceptibility to artemisinin, chloroquine, and mefloquine

The clinical efficacy of oral and intravenous (iv) artesunate was compared in an open randomized trial in 50 male adult patients with uncomplicated Plasmodium falciparum malaria in Kibaha, Tanzania. Oral artesunate treatment was started with 2 x 50 mg initially followed by 50 mg 12 hr later and then 50 mg twice a day for four days (total dose = 550 mg or 9.6 mg/kg). Intravenous artesunate administration began with 2 x 0.8 mg/kg initially followed by 0.8 mg/kg 12 hr later and then 0.8 mg/kg twice a day for four days (total dose = 8.8 mg/kg). The mean +/- SD parasite clearance times (PCTs) were nearly identical at 23.4 +/- 5.9 hr and 24.2 +/- 7.2 hr after oral and iv administration, respectively. Mean +/- SD fever subsidence times (FSTs) were also similar at 18.7 +/- 8.3 hr and 21.0 +/- 4.8 hr, respectively. All patients remained negative for P. falciparum for at least 14 days. Recrudescence/reinfection occurred between days 21 and 28 in five of 25 patients (20%) after oral treatment and in four of 25 patients (16%) after iv treatment. The mean erythrocyte count and hemoglobin concentration were slightly reduced after iv treatment but remained in the normal range. Otherwise, there was no change in blood biochemistry, hematology, and electrocardiograms monitored prior to and during the last dose. It is concluded that treatment with oral and iv artesunate was equally efficacious and well tolerated. A 24-hr in vitro susceptibility test of P. falciparum to artemisinin, chloroquine, and mefloquine was performed in samples from all patients. The three compounds exhibited 100% inhibition with the exception of three isolates, which showed chloroquine resistance. Parameter estimates of a sigmoid Emax model (drug concentration at which 50% of the growth inhibition occurs [EC50]), the sigmoidicity factor s and EC95 fitted to the growth inhibition data differed between compounds and isolates, indicating different sensitivity of P. falciparum isolates. There was no correlation between artemisinin and mefloquine EC50 values, while artemisinin and chloroquine EC50 values showed weak correlation (r2 = 0.223, P = 0.006). There was no correlation between parameters describing clinical outcome (the PCT, the time needed for reduction of the parasite density to 50% and 95% of the initial parasitemia, and the FST) and those describing in vitro susceptibility.

Concentration and time dependency of artemisinin efficacy against Plasmodium falciparum in vitro

A chloroquine-sensitive strain of Plasmodium falciparum, F32, from Tanzania was exposed during continuous culture to concentrations of artemisinin, 10(-8)-10(-5) M, with exposure times ranging from 1 to 96 hr. After drug exposure, the cultures were washed and the incubation was continued for one or two parasite cycles to assess the remaining viability of the parasites. Artemisinin at a concentration of 10(-6) M inhibited parasite growth by 63% within 3 hr of drug exposure. The parasitemia then continued to decrease after removing the drug by washing the cultures. A 95% inhibition was thus observed 48 hr later. For 100% inhibition, at least 12 hr of exposure to 10(-6) M artemisinin was required. The compound at a concentration of 10(-7) M inhibited growth by 86% within 24 hr of drug exposure and by 98% 48 hours after removing the drug. A concentration of 3 x 10(-8) M exhibited 97-100% inhibition only after 72 or 96 hr of drug exposure, while 10(-8) M did not have any appreciable effect on the growth of the parasites even after 96 hr. It is concluded that artemisinin at high concentrations has a significant rapid in vitro effect that appears to be highly parasitocidal. The compound appears to have a broad spectrum of action, not only schizontocidal as reported earlier, but also against the asexual blood stages of P. falciparum.

Suppression of Plasmodium falciparum infections during concomitant measles or influenza but not during pertussis

In tropical countries, concomitant infections are a continuous problem. In the Rufiji Delta, an area of Tanzania that is holoendemic for malaria, there were outbreaks of influenza A, measles, and pertussis in 1986 and 1987. Significantly lower parasitic prevalences and mean densities of malaria parasites were found in children up to nine years of age who had measles or influenza than in asymptomatic control children. In contrast, children with pertussis had a higher prevalence and mean density than controls. The clinical courses of measles, influenza, or pertussis infections did not appear to be significantly affected by concomitant malaria infections. The reasons for the suppression of Plasmodium falciparum parasitemia during these viral infections are unclear. This effect could not be explained by the presence of fever.

Clinical and parasitological studies on malaria in Liberian adults living under intense malaria transmission

Occurrence of fevers and chills, headaches and body and joint pains, and body temperature and malaria parasitaemias were recorded monthly for a year for 121 Liberian adults. There was no apparent correlation between any of the symptoms and the presence or density of blood parasites; it was therefore not possible to define a case of clinical malaria in the study population, which was probably highly immune to infection. Only a few people with patent blood infections had elevated blood temperatures and these were below 37.5 degrees C. Malaria prevalence and levels of parasitaemia declined with age and indicated that immunity continues to develop well into adult age. The data did not support the view that adults experience symptoms at lower parasitaemias than children. Pregnant and non-pregnant women had similar levels of symptoms, but high levels of parasitaemia were found more frequently in the pregnant group.

Plasmodium falciparum reinfection in children from a holoendemic area in relation to seroreactivities against oligopeptides from different malaria antigens

The rate and densities of Plasmodium falciparum reinfections were investigated in children five to 14 years old from one village in Tanzania with a high transmission rate. Initial parasitemias were eradicated by a curative treatment with quinine, a drug with a short elimination half-life, to minimize the effects of residual drug on reinfection. The seroreactivities to seven oligopeptides, representing T and B cell epitopes from the ring erythrocyte surface antigen (Pf155/RESA), the clustered arginine-rich protein antigen (CARP), and the circumsporozoite (CS) proteins were determined in the children at the start of the study and after 28 days. All children were reinfected within 42 days (mean 27 days). The geometric mean maximum parasite density at reinfection was 308 parasites per microliter (range 4-13, 920). The antipeptide antibody levels showed high interindividual variation, with a significant mean decrease (16%) between days 0 and 28 for the blood stage antigens, but not for the (NANP)6 peptide from the CS protein. This suggests that the absence of blood stage antigenic stimulation had already influenced the antibody levels within this short period of time. The mean reinfection day was not influenced by the levels of antibodies to any of the peptides. However, the children with higher antibody levels to (EENVEHDA)2(EENV)2 developed significantly lower parasitemias than those with lower antibody levels (P less than 0.05). This suggests that this subunit of the Pf155/RESA molecule is an important B cell epitope for protective antiparasitic immunity.

A longitudinal study of seroreactivities to Plasmodium falciparum antigens in infants and children living in a holoendemic area of Liberia

Investigators studied 348 children age 0-10 years, living in a holoendemic area of Liberia, for parasitological, serological and clinical parameters. The age-specific parasite rate increased towards the 7-10 year-old age group in which it was 86.8%. The geometrical mean parasite density decreased from the 3-4 year-old age group, in which fewer episodes of clinical malaria were observed. Antibodies to crude Plasmodium falciparum parasite antigens were detected in all children. The (EENV)6 seropositive rate was a maximum of 67.9% in the 3-11 month-old age group. It declined to a minimum of 31.7% in the 5-6 years age group after which it increased slowly in the 7-10 years age group. Antibodies to the synthetic peptide (NANP)6 showed a steady seropositive rate after the age of 3 months, between 30.0% and 39.3% in all the age groups up to 10 years. No statistically significant correlation was found between seropositivity to (EENV)6 and malarial parasitemia. In contrast, a statistically significant positive correlation was found between seropositivity to (NANP)6 and parasite rates. The antibody response for the individual child was transient to both Pf155/RESA, measured by immunofluorescence, and to (EENV)6 and (NANP)6, measured by ELISA, especially in the younger age groups of this study population. Parasitological and clinical immunity developed before a stable antibody response to these defined malaria antigens was established. These antibodies may still contribute to the immune protection against malaria, but they were not reliable parameters for protective immunity in the population we studied.

In vitro and in vivo susceptibility of Plasmodium falciparum isolates from Liberia to pyrimethamine, cycloguanil and chlorcycloguanil

In vivo susceptibility of Plasmodium falciparum to chlorproguanil and in vitro susceptibility to pyrimethamine, cycloguanil and chlorcycloguanil were studied in 38 children from two Liberian villages. Children in one village (Lagbala) had received monthly chemosuppression with chlorproguanil from 1976-1985, and children in the other village (JDF) had received fortnightly chlorproguanil from 1981-1985. The highest and lowest IC100 for pyrimethamine differed by a factor of 10(5), but they differed only by a factor of 10(3) for chlorcycloguanil. The mean IC100 for chlorcycloguanil was significantly lower (P less than 0.0001) than the mean IC100 for pyrimethamine and cycloguanil, and the IC100 for the samples most resistant to chlorcycloguanil (10(-8) M) was still well below peak blood concentrations after chlorproguanil administration. Resistance could be defined as IC100 greater than or equal to 10(-6) M for pyrimethamine and IC100 greater than or equal to 10(-8) M for chlorcycloguanil. The isolates most resistant or most sensitive to pyrimethamine were also the most resistant or most sensitive to chlorcycloguanil, indicating partial cross-resistance between the two drugs. The in vivo response to chlorproguanil 1.5 mg kg-1 in Lagbala was equal to the response in 1983. Chlorproguanil 1.5 mg kg-1 resulted in lower parasite rates on day 3 and 7, but did not prevent 60% of the children requiring treatment with chloroquine during the four weeks' follow-up after chlorproguanil administration.