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In areas of moderate to intense Plasmodium falciparum transmission, malaria in pregnancy remains a significant cause of low birth weight, stillbirth, and severe anaemia. Previously, fetal sex has been identified to modify the risks of maternal asthma, pre-eclampsia, and gestational diabetes. One study demonstrated increased risk of placental malaria in women carrying a female fetus. We investigated the association between fetal sex and malaria in pregnancy in 11 pregnancy studies conducted in sub-Saharan African countries and Papua New Guinea through meta-analysis using log binomial regression fitted to a random-effects model. Malaria infection during pregnancy and delivery was assessed using light microscopy, polymerase chain reaction, and histology. Five studies were observational studies and six were randomised controlled trials. Studies varied in terms of gravidity, gestational age at antenatal enrolment and bed net use. Presence of a female fetus was associated with malaria infection at enrolment by light microscopy (risk ratio 1.14 [95% confidence interval 1.04, 1.24]; P = 0.003; n = 11,729). Fetal sex did not associate with malaria infection when other time points or diagnostic methods were used. There is limited evidence that fetal sex influences the risk of malaria infection in pregnancy., (© 2023. The Author(s).)

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., (© 2022. The Author(s).)

Background: The provision of post-discharge malaria chemoprevention (PMC) in children recently admitted with severe anemia reduces the risk of death and re-admissions in malaria endemic countries. The main objective of this trial was to identify the most effective method of delivering dihydroartemesinin-piperaquine to children recovering from severe anemia., Methods: This was a 5-arm, cluster-randomized trial among under-5 children hospitalized with severe anemia at Zomba Central Hospital in Southern Malawi. Children were randomized to receive three day treatment doses of dihydroartemesinin-piperaquine monthly either; 1) in the community without a short text reminder; 2) in the community with a short message reminder; 3) in the community with a community health worker reminder; 4) at the facility without a short text reminder; or 5) at the facility with a short message reminder. The primary outcome measure was adherence to all treatment doses of dihydroartemesinin-piperaquine and this was assessed by pill-counts done by field workers during home visits. Poisson regression was utilized for analysis., Results: Between March 2016 and October 2018, 1460 clusters were randomized. A total of 667 children were screened and 375 from 329 clusters were eligible and enrolled from the hospital. Adherence was higher in all three community-based compared to the two facility-based delivery (156/221 [70·6%] vs. 78/150 [52·0%], IRR = 1·24,95%CI 1·06-1·44, p = 0·006). This was observed in both the SMS group (IRR = 1·41,1·21-1·64, p<0·001) and in the non-SMS group (IRR = 1·37,1·18-1·61, p<0·001). Although adherence was higher among SMS recipients (98/148 66·2%] vs. non-SMS 82/144 (56·9%), there was no statistical evidence that SMS reminders resulted in greater adherence ([IRR = 1·03,0·88-1·21, p = 0·68). When compared to the facility-based non-SMS arm (control arm), community-based delivery utilizing CHWs resulted in higher adherence [39/76 (51·3%) vs. 54/79 (68·4%), IRR = 1·32, 1·14-1·54, p<0·001]., Interpretation: Community-based delivery of dihydroartemesinin-piperaquine for post-discharge malaria chemoprevention in children recovering from severe anemia resulted in higher adherence compared to facility-based methods., Trial Registration: NCT02721420; ClinicalTrials.gov., Competing Interests: The authors have declared that no competing interests exist.

Background: Simultaneous infection with multiple malaria parasite strains is common in high transmission areas. Quantifying the number of strains per host, or the multiplicity of infection (MOI), provides additional parasite indices for assessing transmission levels but it is challenging to measure accurately with current tools. This paper presents new laboratory and analytical methods for estimating the MOI of Plasmodium falciparum., Methods: Based on 24 single nucleotide polymorphisms (SNPs) previously identified as stable, unlinked targets across 12 of the 14 chromosomes within P. falciparum genome, three multiplex PCRs of short target regions and subsequent next generation sequencing (NGS) of the amplicons were developed. A bioinformatics pipeline including B4Screening pathway removed spurious amplicons to ensure consistent frequency calls at each SNP location, compiled amplicons by SNP site diversity, and performed algorithmic haplotype and strain reconstruction. The pipeline was validated by 108 samples generated from cultured-laboratory strain mixtures in different proportions and concentrations, with and without pre-amplification, and using whole blood and dried blood spots (DBS). The pipeline was applied to 273 smear-positive samples from surveys conducted in western Kenya, then providing results into StrainRecon Thresholding for Infection Multiplicity (STIM), a novel MOI estimator., Results: The 24 barcode SNPs were successfully identified uniformly across the 12 chromosomes of P. falciparum in a sample using the pipeline. Pre-amplification and parasite concentration, while non-linearly associated with SNP read depth, did not influence the SNP frequency calls. Based on consistent SNP frequency calls at targeted locations, the algorithmic strain reconstruction for each laboratory-mixed sample had 98.5% accuracy in dominant strains. STIM detected up to 5 strains in field samples from western Kenya and showed declining MOI over time (q < 0.02), from 4.32 strains per infected person in 1996 to 4.01, 3.56 and 3.35 in 2001, 2007 and 2012, and a reduction in the proportion of samples with 5 strains from 57% in 1996 to 18% in 2012., Conclusion: The combined approach of new multiplex PCRs and NGS, the unique bioinformatics pipeline and STIM could identify 24 barcode SNPs of P. falciparum correctly and consistently. The methodology could be applied to field samples to reliably measure temporal changes in MOI.

Background: Malaria in pregnancy poses a major public health problem in Indonesia with an estimated six million pregnancies at risk of Plasmodium falciparum or Plasmodium vivax malaria annually. In 2010, Indonesia introduced a screen and treat policy for the control of malaria in pregnancy at first antenatal visit using microscopy or rapid diagnostic tests (RDTs). A diagnostic study was conducted in Sumba, Indonesia to compare the performance of four different RDTs in predominately asymptomatic pregnant women under field condition., Methods: Women were screened for malaria at antenatal visits using field microscopy and four HRP-2/pLDH combination RDTs (Carestart™, First-Response(®), Parascreen(®) and SD-Bioline(®)). The test results were compared with expert microscopy and nested PCR. End user experience of the RDTs in the field was assessed by questionnaire., Results: Overall 950 were recruited and 98.7 % were asymptomatic. The prevalence of malaria was 3.0-3.4 % by RDTs, and 3.6, 5.0 and 6.6 % by field microscopy, expert microscopy and PCR, respectively. The geometric-mean parasite density was low (P. falciparum = 418, P. vivax = 147 parasites/µL). Compared with PCR, the overall sensitivity of the RDTs and field microscopy to detect any species was 24.6-31.1 %; specificities were >98.4 %. Relative to PCR, First-Response(®) had the best diagnostic accuracy (any species): sensitivity = 31.1 %, specificity = 98.9 % and diagnostic odds ratio = 39.0 (DOR). The DOR values for Carestart™, Parascreen(®), SD-Bioline(®), and field microscopy were 23.4, 23.7, 23.5 and 29.2, respectively. The sensitivity of Pan-pLDH bands to detect PCR confirmed P. vivax mono-infection were 8.6-13.0 %. The sensitivity of the HRP-2 band alone to detect PCR confirmed P. falciparum was 10.3-17.9 %. Pan-pLDH detected P. falciparum cases undetected by the HRP-2 band resulting in a better test performance when both bands were combined. First Response(®) was preferred by end-users for the overall practicality., Conclusion: The diagnostic accuracy to detect malaria among mostly asymptomatic pregnant women and perceived ease of use was slightly better with First-Response(®), but overall, differences between the four RDTs were small and performance comparable to field microscopy. Combination RDTs are a suitable alternative to field microscopy to screen for malaria in pregnancy in rural Indonesia. The clinical relevance of low density malaria infections detected by PCR, but undetected by RDTs or microscopy needs to be determined.

Background: Although it is well known that drug pressure selects for drug-resistant parasites, the role of transmission reduction by insecticide-treated bed nets (ITNs) on drug resistance remains unclear. In this study, the drug resistance profile of current and previous first-line anti-malarials in Kenya was assessed within the context of drug policy change and scale-up of ITNs. National first-line treatment changed from chloroquine (CQ) to sulphadoxine-pyrimethamine (SP) in 1998 and to artemether-lumefantrine (AL) in 2004. ITN use was scaled-up in the Asembo, Gem and Karemo areas of western Kenya in 1997, 1999 and 2006, respectively., Methods: Smear-positive samples (N = 253) collected from a 2007 cross-sectional survey among children in Asembo, Gem and Karemo were genotyped for mutations in pfcrt and pfmdr1 (CQ), dhfr and dhps (SP), and at pfmdr-N86 and the gene copy number in pfmdr1 (lumefantrine). Results were compared among the three geographic areas in 2007 and to retrospective molecular data from children in Asembo in 2001., Results: In 2007, 69 and 85% of samples harboured the pfmdr1-86Y mutation and dhfr/dhps quintuple mutant, respectively, with no significant differences by study area. However, the prevalence of the pfcrt-76T mutation differed significantly among areas (p <0.02), between 76 and 94%, with the highest prevalence in Asembo. Several 2007 samples carried mutations at dhfr-164L, dhps-436A, or dhps-613T. From 2001 to 2007, there were significant increases in the pfcrt-76T mutation from 82 to 94% (p <0.03), dhfr/dhps quintuple mutant from 62 to 82% (p <0.03), and an increase in the septuple CQ and SP combined mutant haplotype, K 76 Y 86 I 51 R 59 N 108 G 437 E 540 , from 28 to 39%. The prevalence of the pfmdr1-86Y mutation remained unchanged. All samples were single copy for pfmdr1., Conclusions: Molecular markers associated with lumefantrine resistance were not detected in 2007. More recent samples will be needed to detect any selective effects by AL. The prevalence of CQ and SP resistance markers increased from 2001 to 2007 in the absence of changes in transmission intensity. In 2007, only the prevalence of pfcrt-76T mutation differed among study areas of varying transmission intensity. Resistant parasites were most likely selected by sustained drug pressure from the continued use of CQ, SP, and mechanistically similar drugs, such as amodiaquine and cotrimoxazole. There was no clear evidence that differences in transmission intensity, as a result of ITN scale-up, influenced the prevalence of drug resistance molecular markers.

Indirect clinical measures assessing anti-malarial drug transmission-blocking activity in falciparum malaria include measurement of the duration of gametocytaemia, the rate of gametocyte clearance or the area under the gametocytaemia-time curve (AUC). These may provide useful comparative information, but they underestimate dose-response relationships for transmission-blocking activity. Following 8-aminoquinoline administration P. falciparum gametocytes are sterilized within hours, whereas clearance from blood takes days. Gametocytaemia AUC and clearance times are determined predominantly by the more numerous female gametocytes, which are generally less drug sensitive than the minority male gametocytes, whereas transmission-blocking activity and thus infectivity is determined by the more sensitive male forms. In choosing doses of transmission-blocking drugs there is no substitute yet for mosquito-feeding studies.

Background: Although several studies have investigated the impact of reduced malaria transmission due to insecticide-treated bed nets (ITNs) on the patterns of morbidity and mortality, there is limited information on their effect on parasite diversity., Methods: Sequencing was used to investigate the effect of ITNs on polymorphisms in two genes encoding leading Plasmodium falciparum vaccine candidate antigens, the 19 kilodalton blood stage merozoite surface protein-1 (MSP-1(19kDa)) and the Th2R and Th3R T-cell epitopes of the pre-erythrocytic stage circumsporozoite protein (CSP) in a large community-based ITN trial site in western Kenya. The number and frequency of haplotypes as well as nucleotide and haplotype diversity were compared among parasites obtained from children <5 years old prior to the introduction of ITNs (1996) and after 5 years of high coverage ITN use (2001)., Results: A total of 12 MSP-1(19kDa) haplotypes were detected in 1996 and 2001. The Q-KSNG-L and E-KSNG-L haplotypes corresponding to the FVO and FUP strains of P. falciparum were the most prevalent (range 32-37%), with an overall haplotype diversity of > 0.7. No MSP-1(19kDa) 3D7 sequence-types were detected in 1996 and the frequency was less than 4% in 2001. The CSP Th2R and Th3R domains were highly polymorphic with a total of 26 and 14 haplotypes, respectively detected in 1996 and 34 and 13 haplotypes in 2001, with an overall haplotype diversity of > 0.9 and 0.75 respectively. The frequency of the most predominant Th2R and Th3R haplotypes was 14 and 36%, respectively. The frequency of Th2R and Th3R haplotypes corresponding to the 3D7 parasite strain was less than 4% at both time points. There was no significant difference in nucleotide and haplotype diversity in parasite isolates collected at both time points., Conclusion: High diversity in these two genes has been maintained overtime despite marked reductions in malaria transmission due to ITNs use. The frequency of 3D7 sequence-types was very low in this area. These findings provide information that could be useful in the design of future malaria vaccines for deployment in endemic areas with high ITN coverage and in interpretation of efficacy data for malaria vaccines based on 3D7 parasite strains.

Plasmodium falciparum placental infection during pregnancy is harmful for both mother and child. Protection from placental infection is parity-dependent, that is, acquired over consecutive pregnancies. However, the infection status of the placenta can only be assessed at delivery. Here, to better understand the mechanism underlying this parity-dependence, we fitted a model linking malaria dynamics within the general population to observed placental histology. Our results suggest that immunity resulting in less prolonged infection is a greater determinant of the parity-specific patterns than immunity that prevents placental sequestration. Our results also suggest the time when maternal blood first flows into the placenta is a high-risk period. Therefore, preventative strategies implementable before or early in pregnancy, such as insecticide-treated net usage in women of child-bearing age or any future vaccine, could substantially reduce the number of women who experience placental infection.

Background: Understanding the origin and spread of mutations associated with drug resistance, especially in the context of combination therapy, will help guide strategies to halt and prevent the emergence of resistance. Unfortunately, studies have assessed these complex processes when resistance is already highly prevalent. Even further, information on the evolutionary dynamics leading to multidrug-resistant parasites is scattered and limited to areas with low or seasonal malaria transmission. This study describes the dynamics of strong selection for mutations conferring resistance against sulphadoxine-pyrimethamine (SP), a combination therapy, in western Kenya between 1992 and 1999, just before SP became first-line therapy (1999). Importantly, the study is based on longitudinal data, which allows for a comprehensive analysis that contrasts with previous cross-sectional studies carried out in other endemic regions., Methods: This study used 236 blood samples collected between 1992 and 1999 in the Asembo Bay area of Kenya. Pyrosequencing was used to determine the alleles of dihydrofolate reductase (dhfr) and dihydropterote synthase (dhps) genes. Microsatellite alleles spanning 138 kb around dhfr and dhps, as well as, neutral markers spanning approximately 100 kb on chromosomes 2 and 3 were characterized., Results: By 1992, the South-Asian dhfr triple mutant was already spreading, albeit in low frequency, in this holoendemic Kenyan population, prior to the use of SP as a first-line therapy. Additionally, dhfr triple mutant alleles that originated independently from the predominant Southeast Asian lineage were present in the sample set. Likewise, dhps double mutants were already present as early as 1992. There is evidence for soft selective sweeps of two dhfr mutant alleles and the possible emergence of a selective sweep of double mutant dhps alleles between 1992 and 1997. The longitudinal structure of the dataset allowed estimation of selection pressures on various dhfr and dhps mutants relative to each other based on a theoretical model tailored to P. falciparum. The data indicate that drug selection acted differently on the resistant alleles of dhfr and dhps, as evidenced by fitness differences. Thus a combination drug therapy such as SP, by itself, does not appear to select for "multidrug"-resistant parasites in areas with high recombination rate., Conclusions: The complexity of these observations emphasizes the importance of population-based studies to evaluate the effects of strong drug selection on Plasmodium falciparum populations.

Despite the clear public health benefit of insecticide-treated bednets (ITNs), the impact of malaria transmission-reduction by vector control on the spread of drug resistance is not well understood. In the present study, the effect of sustained transmission reduction by ITNs on the prevalence of Plasmodium falciparum gene mutations associated with resistance to the antimalarial drugs sulfadoxine-pyrimethamine (SP) and chloroquine (CQ) in children under the age of five years was investigated during an ITN trial in Asembo area, western Kenya. During the ITN trial, the national first line antimalarial treatment changed from CQ to SP. Smear-positive samples collected from cross sectional surveys prior to ITN introduction (baseline, n = 250) and five years post-ITN intervention (year 5 survey, n = 242) were genotyped for single nucleotide polymorphisms (SNPs) at dhfr-51, 59, 108, 164 and dhps-437, 540 (SP resistance), and pfcrt-76 and pfmdr1-86 (CQ resistance). The association between the drug resistance mutations and epidemiological variables was evaluated. There were significant increases in the prevalence of SP dhps mutations and the dhfr/dhps quintuple mutant, and a significant reduction in the proportion of mixed infections detected at dhfr-51, 59 and dhps-437, 540 SNPs from baseline to the year 5 survey. There was no change in the high prevalence of pfcrt-76 and pfmdr1-86 mutations. Multivariable regression analysis further showed that current antifolate use and year of survey were significantly associated with more SP drug resistance mutations. These results suggest that increased antifolate drug use due to drug policy change likely led to the high prevalence of SP mutations 5 years post-ITN intervention and reduced transmission had no apparent effect on the existing high prevalence of CQ mutations. There is no evidence from the current study that sustained transmission reduction by ITNs reduces the prevalence of genes associated with malaria drug resistance.

Background: Insecticide-treated bed nets (ITNs) reduce malaria transmission and are an important prevention tool. However, there are still information gaps on how the reduction in malaria transmission by ITNs affects parasite genetics population structure. This study examined the relationship between transmission reduction from ITN use and the population genetic diversity of Plasmodium falciparum in an area of high ITN coverage in western Kenya., Methods: Parasite genetic diversity was assessed by scoring eight single copy neutral multilocus microsatellite (MS) markers in samples collected from P. falciparum-infected children (< five years) before introduction of ITNs (1996, baseline, n = 69) and five years after intervention (2001, follow-up, n = 74)., Results: There were no significant changes in overall high mixed infections and unbiased expected heterozygosity between baseline (%MA = 94% and He = 0.75) and follow up (%MA = 95% and He = 0.79) years. However, locus specific analysis detected significant differences for some individual loci between the two time points. Pfg377 loci, a gametocyte-specific MS marker showed significant increase in mixed infections and He in the follow up survey (%MA = 53% and He = 0.57) compared to the baseline (%MA = 30% and He = 0.29). An opposite trend was observed in the erythrocyte binding protein (EBP) MS marker. There was moderate genetic differentiation at the Pfg377 and TAA60 loci (FST = 0.117 and 0.137 respectively) between the baseline and post-ITN parasite populations. Further analysis revealed linkage disequilibrium (LD) of the microsatellites in the baseline (14 significant pair-wise tests and ISA = 0.016) that was broken in the follow up parasite population (6 significant pairs and ISA = 0.0003). The locus specific change in He, the moderate population differentiation and break in LD between the baseline and follow up years suggest an underlying change in population sub-structure despite the stability in the overall genetic diversity and multiple infection levels., Conclusions: The results from this study suggest that although P. falciparum population maintained an overall stability in genetic diversity after five years of high ITN coverage, there was significant locus specific change associated with gametocytes, marking these for further investigation.

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.

Plasmodium falciparum has developed resistance to almost all routinely used antimalarial drugs. Sulfadoxine-pyrimethamine (SP) has replaced chloroquine as first-line treatment of uncomplicated malaria infection in Kenya but resistance to SP is already reported. The addition of artemisinin derivatives to SP may delay the development of drug resistance, improve cure rates, and reduce transmission. The efficacy and safety of artesunate plus SP in the treatment of uncomplicated P. falciparum malaria was evaluated in a randomized trial of 600 children at Siaya District Hospital, western Kenya between October 1999 and March 2000. Children aged < 5 years were randomly assigned to receive SP alone (1.25 mg/kg based on pyrimethamine), or in combination with artesunate (4 mg/kg/d) for either 1 or 3 d. Parasitological failure by days 14 and 28 (polymerase chain reaction [PCR]-corrected for new infections) were the primary endpoints. Treatment failure rates by day 14 were 25.5% in the SP alone group, 16.2% (risk difference [delta]-9.3%, 95% CI -17.3 to -1.2%, P= 0.027) in the 1-dose artesunate group, and 9.4% (delta-16.2%, 95% CI -23.6 to -8.7%, P< 0.001) in the 3-dose artesunate group. Corresponding rates by day 28 were 46.0% in the SP alone group, 38.2% (delta-7.8%, 95% CI -17.7 to 2.1%, P= 0.16) in the 1-dose artesunate group, and 26.0% (delta-20.0%, 95% CI -29.4 to -10.6%, P < 0.001) in the 3-dose artesunate group. The artesunate and SP combination was well tolerated. There were no serious drug-related adverse events. Parasite clearance and gametocyte carriage were reduced significantly in both combination groups compared with SP alone. Three days of artesunate were required to reduce significantly the risk of treatment failure by day 28. However, the high background rate of parasitological failure with SP may make this combination unsuitable for widespread use in Kenya.

Objectives: HIV-seropositive pregnant women are more susceptible to malaria than HIV-seronegative women. We assessed whether HIV infection alters maternal and cord plasma malarial antibody responses and the mother-to-infant transfer of malaria antibodies., Methods: We determined plasma levels of maternal and cord antibodies [Immunoglobulin (IgG)] to recombinant malarial proteins [merozoite surface protein 1 (MSP-1(19kD)), the erythrocyte binding antigen (EBA-175)], the synthetic peptides [MSP-2, MSP-3, rhoptry associated protein 1 (RAP-1), and the pre-erythrocytic stage, circumsporozoite protein (NANP)(5)] antigenic determinants of Plasmodium falciparum; and tetanus toxoid (TT) by ELISA among samples of 99 HIV-seropositive mothers, 69 of their infants, 102 HIV-seronegative mothers and 62 of their infants., Results: The prevalence of maternal antibodies to the malarial antigenic determinants ranged from 18% on MSP3 to 91% on EBA-175; in cord plasma it ranged from 13% to 91%, respectively. More than 97% of maternal and cord samples had antibodies to TT. In multivariate analysis, HIV infection was only associated with reduced antibodies to (NANP)(5) in maternal (P=0.001) and cord plasma (P=0.001); and reduced mother-to-infant antibody transfer to (NANP)(5) (P=0.012). This effect of HIV was independent of maternal age, gravidity and placental malaria. No consistent HIV-associated differences were observed for other antigenic determinants., Conclusion: An effect of HIV infection was only observed on one malarial antigenic determinant, suggesting that the increased susceptibility to malaria among HIV-infected pregnant women may not be explained on the basis of their reduced antibody response to malaria antigens.

We investigated the integrity of the gluconeogenic pathway in severe malaria using alanine metabolism as a measure. Alanine disposition and liver blood flow, assessed by indocyanine green (ICG) clearance, were measured simultaneously in 10 patients with falciparum malaria (six severe and four moderately severe malaria). After intravenous infusion of alanine (0.3 g/kg), glucose increments (AUC0-55 min) were lower in patients with severe malaria than in those with moderately severe malaria (median = 508 vs. 808 mmol/min/l; P = 0.055). There were no significant differences in the other metabolite increments (alanine, lactate and pyruvate; P >/= 0.27). The two fatal cases had markedly delayed alanine removal (larger AUC0-55 min), prolonged T(1/2) and slower clearance (P /= 0.07) but the increments of lactate and pyruvate were lower in convalescence. Thus, the ratio of the increments of alanine to those of lactate and pyruvate were significantly higher in the convalescent study (P

The factors contributing to anemia in falciparum malaria were characterized in 4,007 prospectively studied patients on the western border of Thailand. Of these, 727 patients (18%) presented with anemia (haematocrit < 30%), and 1% (55 of 5,253) required blood transfusion. The following were found to be independent risk factors for anemia at admission: age < 5 years, a palpable spleen, a palpable liver, recrudescent infections, being female, a prolonged history of illness (> 2 days) before admission, and pure Plasmodium falciparum infections rather than mixed P. falciparum and Plasmodium vivax infections. The mean maximum fractional fall in hematocrit after antimalarial treatment was 14.1% of the baseline value (95% confidence interval [CI], 13.6-14.6). This reduction was significantly greater in young children (aged < 5 years) and in patients with a prolonged illness, high parasitemia, or delayed parasite clearance. Loss of parasitized erythrocytes accounted for < 10% of overall red blood cell loss. Hematological recovery was usually complete within 6 weeks, but it was slower in patients who were anemic at admission (adjusted hazards ratio [AHR], 1.9, 95% CI, 1.5-2.3), and those whose infections recrudesced (AHR, 1.2, 95% CI, 1.01-1.5). Half the patients with treatment failure were anemic at 6 weeks compared with 19% of successfully treated patients (relative risk, 2.8, 95% CI, 2.0-3.8). Patients coinfected with P. vivax (16% of the total) were 1.8 (95% CI, 1.2-2.6) times less likely to become anemic and recovered 1.3 (95% CI, 1.0-1.5) times faster than those with P. falciparum only. Anemia is related to drug resistance and treatment failure in uncomplicated malaria. Children aged < 5 years of age were more likely than older children or adults to become anemic. Coinfection with P. vivax attenuates the anemia of falciparum malaria, presumably by modifying the severity of the infection.

A polymorphism in the promoter region of the tumor necrosis factor-alpha (TNF-alpha) gene, with a guanine to adenine nucleotide change at position -308, TNF2 is associated with increased TNF-alpha production. TNF2 homozygotes have a higher risk of severe disease and/or death due to cerebral malaria and other infectious diseases. We investigated the impact of this allele on malaria morbidity and mortality in young children who participated in an immuno-epidemiologic cohort study of malaria in an area of intense perennial Plasmodium falciparum transmission in western Kenya. A total of 1,048 children were genotyped. Poisson regression and Cox proportional hazards models were used to determine the relationship between TNF-308 variants and morbidity and mortality. The gene frequencies of the TNF1 and TNF2 alleles were 0.90 and 0.10, respectively. TNF2 homozygosity was associated with pre-term birth when compared with TNF1 homozygotes [relative risk (RR) 7.3, 95% CI, 2.85-18.9, P = 0.002) and heterozygotes (RR 6.7, 95% CI 2.0-23.0, P = 0.008). Among children born prematurely, the TNF2 allele was significantly associated with a higher risk of death in infancy compared with TNF1 (RR 7.47, 95% CI 2.36-23.6). The risk of death was higher among TNF2 homozygotes than among heterozygotes. The TNF2 allele was significantly associated with high density P. falciparum parasitemia (RR 1.11, 95% CI 1.0-1.24). Among low birth weight children, the TNF2 allele was associated with severe anemia (RR 2.16, 95% CI 1.17-4.01) and showed a trend toward a risk for severe malaria anemia (RR 1.99, 95% CI 0.89-4.46). These data suggest that TNF2 is a risk factor for pre-term birth and early childhood mortality and malaria morbidity in children in this region. Further understanding of the pathogenic mechanisms underlying this association is required., (Copyright 2001 Wiley-Liss, Inc.)

Background: Worsening drug resistance in Plasmodium falciparum malaria is a major threat to health in tropical countries. We did a prospective study of malaria incidence and treatment in an area of highly multidrug-resistant P. falciparum malaria., Methods: We assessed incidence of P. falciparum malaria and the in-vivo responses to mefloquine treatment over 13 years in two large camps for displaced Karen people on the northwest border of Thailand. During this time, the standard mefloquine dose was first increased, and then combined artesunate and mefloquine was introduced as first-line treatment for uncomplicated P. falciparum malaria., Findings: Early detection and treatment controlled P. falciparum malaria initially while mefloquine was effective (cure rate with mefloquine [15 mg/kg] and sulphadoxine-pyrimethamine in 1985, 98% [95% CI 97-100]), but as mefloquine resistance developed, the cure rate fell (71% [67-77] in 1990). A similar pattern was seen for high-dose (25 mg/kg) mefloquine monotherapy from 1990-94. Since the general deployment of the artesunate-mefloquine combination in 1994, the cure rate increased again to almost 100% from 1998 onwards, and there has been a sustained decline in the incidence of P. falciparum malaria in the study area. In-vitro susceptibility of P. falciparum to mefloquine has improved significantly (p=0.003)., Interpretation: In this area of low malaria transmission, early diagnosis and treatment with combined artesunate and mefloquine has reduced the incidence of P. falciparum malaria and halted the progression of mefloquine resistance. We recommend that antimalarial drugs should be combined with artemisinin or a derivative to protect them against resistance.

The relative importance of acute high-density versus persistent low-density Plasmodium falciparum parasitemia in contributing to the public health problem of malarial anemia remains unclear. The Asembo Bay Cohort Project in western Kenya collected monthly hemoglobin (Hb) and parasitologic measurements and biweekly assessments of antimalarial drug use among 942 singleton live births between 1992 and 1996. A mixed-model analysis appropriate for repeated measures data was used to study how time-varying parasitemia and antimalarial drug exposures influenced mean Hb profiles. Incidence of World Health Organization-defined severe malarial anemia was 28.1 per 1,000 person-years. Among children aged less than 24 months, concurrent parasitemia was significantly associated with lower mean Hb, especially when compared to children with no concurrent parasitemia. Increased densities of the 90-day history of parasitemia preceding Hb measurement was more strongly associated with mean Hb levels than concurrent parasitemia density. While the highest quartile of 90-day parasitemia history was associated with lowest mean Hb levels, children in the lowest 90-day exposure quartile still experienced significantly lower Hb levels when compared to children who remained parasitemia-free for the same 90-day period. The results highlight the importance of collecting and analyzing longitudinal Hb and parasitologic data when studying the natural history of malarial anemia.

Objective: To construct a population pharmacokinetic model for mefloquine in the treatment of falciparum malaria., Background: Mefloquine is the treatment of choice for multidrug-resistant falciparum malaria. The factors that influence the pharmacokinetic properties of mefloquine in acute malaria are not well characterized., Methods: The pharmacokinetic properties of mefloquine were evaluated in 257 patients with acute falciparum malaria by use of nonlinear mixed-effects modeling. Two different oral dose regimens were used: (1) a split dose of 15 mg base/kg initially followed by 10 mg/kg 24 hours later (n = 159) and (2) a single dose of 25 mg/kg (n = 98). Mefloquine was combined with artesunate in 105 (41%) patients (74 received a split dose and 31 received a single dose)., Results: Splitting the mefloquine dose increased the area under the concentration-time curve [AUC(0-infinity)] by 50% (95% confidence interval [CI], 36% to 65%) for monotherapy and by 20% (95% CI, 3% to 40%) for combined therapy. The apparent volume of distribution (V/F) was significantly lower in patients receiving split doses of mefloquine monotherapy (mean, 8.14 L/kg; 95% CI, 7.49 to 8.86 L/kg) compared with a single dose (mean, 20.37 L/kg; 95% CI, 16.26 to 25.51 L/kg). Patients who received mefloquine monotherapy and cleared parasitemia in less than 48 hours had a significantly higher AUC(0-infinity) independent of any confounders, compared with patients with slower parasite clearance (geometric mean [95% CI], 50,373 ng/mL x day [46,121 to 55,017 ng/mL x day] versus 45,583 ng/mL x day [42,306 to 49,125 ng/mL x day])., Conclusions: The pharmacokinetic properties of mefloquine in malaria were relatively unaffected by demographic variables (other than body weight) or disease severity. If it is assumed that apparent clearance and volume of distribution are unaffected by dose regimen, then splitting the 25 mg/kg mefloquine dose improves oral bioavailability and the therapeutic response in the treatment of acute falciparum malaria.

The factors affecting the development of patent Plasmodium falciparum gametocytemia were assessed in 5,682 patients entered prospectively into a series of antimalarial drug trials conducted in an area of low and seasonal transmission on the western border of Thailand. Of the 4,565 patients with admission thick smear assessments, 110 (2.4%) had gametocytemia. During the follow-up period 170 (3%) of all patients developed patent gametocytemia, which in 89% had developed by day 14 following treatment. In a multiple logistic regression model five factors were found to be independent risk factors at presentation for the development or persistence of gametocytemia during follow up; patent gametocytemia on admission (adjusted odds ratio [AOR] = 7.8, 95% confidence interval [CI] = 3.7-16, P < 0.001), anemia (hematocrit <30%) (AOR = 3.9, 95% CI = 2.3-6.5, P < 0.001), no coincident P. vivax malaria (AOR = 3.5, 95% CI = 1.04-11.5, P < 0.04), presentation with a recrudescent infection (AOR = 2.3, 95% CI = 1.3-4.1, P < 0.004), and a history of illness longer than two days (AOR = 3.3, 95% CI = 1.7-6.6, P < 0.001). Patients whose infections responded slowly to treatment or recrudesced subsequently were also more likely to carry gametocytes than those who responded rapidly or were cured (relative risks = 1.9, 95% CI = 1.3-2.7 and 2.8, 95% CI = 2.0-4.0, respectively; P < 0.001). These data provide further evidence of important epidemiologic interactions between P. falciparum and P. vivax, and drug resistance and transmission potential.

In prospective studies of acute uncomplicated, multidrug-resistant falciparum malaria on the western border of Thailand, the oral artemisinin derivatives were used alone in the treatment of 836 patients (artesunate 630, artemether 206), were combined with mefloquine (15-25 mg base/kg) in 2,826 patients, and mefloquine alone was used in 1,303 patients. The combined regimens of mefloquine plus an artemisinin derivative were associated with more side effects than those with an artemisinin derivative alone; acute nausea (31% versus 16%), vomiting (24% versus 11%), anorexia (51% versus 34%), and dizziness (47% versus 15%) (P < 0.001). Oral artesunate and artemether alone were very well tolerated. There was no difference in the incidence of possible adverse effects between the two drugs, and no evidence that either derivative caused allergic reactions, neurologic or psychiatric reactions, or cardiovascular or dermatologic toxicity. Blackwater fever occurred in three patients treated with mefloquine plus artesunate regimens. Oral artesunate and artemether are safe and well tolerated antimalarial drugs.

Background: Thiamine deficiency (beriberi) is common in some parts of southeast Asia. Acute thiamine deficiency can mimic many complications of malaria, such as encephalopathy and lactic acidosis. We examined the incidence of thiamine deficiency in adults admitted to hospital with malaria in Thailand., Methods: For this prospective study, we recruited consecutive patients with malaria or other febrile illness who presented to Paholpolpayuhasena Hospital, Kanchanaburi, Thailand, between May and July, 1992. We used the activation coefficient (alpha) for transketolase activity in erythrocytes to measure thiamine deficiency (defined as alpha>1.31) in patients with severe and uncomplicated malaria and in controls (patients' relatives and healthy volunteers). To exclude the possibility of interference in the assays, transketolase activity was also measured in erythrocytes used to culture parasites., Findings: 12 (52%) of 23 patients with severe malaria and ten (19%) of 54 patients with uncomplicated malaria had alpha values above the normal range (p<0.0001 and p=0.0014, respectively, compared with controls), which indicated severe thiamine deficiency. Thiamine deficiency was more severe in patients with cerebral malaria than in those with uncomplicated malaria and the controls (p=0.008)., Interpretation: In adults admitted to hospital in Thailand, thiamine deficiency commonly complicates acute falciparum malaria, particularly in severe infections, and could contribute to dysfunction of the central nervous system.

In an area where multi-drug resistance in Plasmodium falciparum is a particular problem, more than 500 children under 5 years of age weighing > 5 kg were treated with mefloquine, either alone or combined with an artemisinin derivative, and followed up for a minimum of 28 days. The principal adverse effect was vomiting and this was associated with reduced efficacy of treatment (even when treatment was repeated). Later adverse effects occurred less frequently than in adults. There was no serious toxicity and, in particular, there were no neuropsychiatric side-effects. The high dose of mefloquine (25 mg/kg) required in this area is well tolerated by young children. It should be given in a divided dose of 15 mg/kg initially, followed by 10 mg/kg > or = 12 hours later.

Background: On the western border of Thailand the efficacy of mefloquine in the treatment of falciparum malaria has declined while gametocyte carriage rates have increased, which suggests increased transmissibility of these resistant infections. We compared the following antimalarial drugs in relation to subsequent Plasmodium falciparum gametocyte carriage: mefloquine, halofantrine, quinine, and the artemisinin derivatives., Methods: Between 1990 and 1995 we assessed gametocytaemia in a series of prospective studies of antimalarial drug treatment in 5193 adults and children with acute uncomplicated falciparum malaria in an area of malarious hill forest on the western border of Thailand. Weekly parasite counts from thick and thin blood films were done during the 4-week (1990-93) or 9-week (1993-95) follow-up period. Gametocyte positivity rates and person gametocyte week (PGW) rates were calculated to measure gametocyte carriage and transmission potential., Findings: In primary P falciparum infections the gametocyte carriage rate was significantly higher after treatment with mefloquine than after treatment with the artemisinin derivatives (PGW 34.1 [95% CI 25.2-42.9] vs 3.9 [1.9-5.9] per 1000 person weeks; relative risk 8.0 [4.1-15.6]; p<0.0001). Recrudescent infections were associated with increased gametocyte carrier rates (relative risk 2.2 [1.6-3.0]; p<0.0001), but retreatment with artemisinin derivatives reduced subsequent gametocyte carriage 18.5 fold [3.5-98] compared with mefloquine retreatment and 6.8 fold (3.1-15.1) compared with quinine retreatment (p<0.001). The introduction of the artemisinin derivatives in routine treatment at this study site in mid 1994 was associated with a reduction in the subsequent incidence of falciparum malaria of 47 (25-69)%, Interpretation: Although environmental changes affect vector numbers, and hence malaria incidence, artemisinin derivatives were found to reduce the transmission potential of falciparum malaria. Widespread introduction of artemisinin derivatives in the treatment of falciparum malaria may prevent the spread of multidrug resistance.

The factors which identify patients at risk of treatment failure were characterized in 1590 children and adults with uncomplicated falciparum malaria treated with 15 or 25 mg/kg of mefloquine on the borders of Thailand. Six independent predictors of failure were identified using multiple logistic regression. Age < or = 2 years (odds ratio [OR] 4.54), 3-15 years (OR 4.4), vomiting < 30 min after a single dose of 25 mg/kg (despite re-administration of the dose) (OR 2.5) and diarrhoea after treatment (OR 3.6) were the strongest predictors of failure by day 7. Parasitaemias > 10 000/mm3 (OR 1.4), and fever with a history of recent vomiting (OR 1.6) were risk factors for recrudescence of the infection between days 10 and 28. Patients treated with mefloquine in the previous 2 months were also at increased risk of failure (OR 2.38), particularly if they were anaemic (haematocrit < 30%) (OR 5.96), which suggested that they had recrudescent infections at presentation. Combined, these 6 factors identified half of all treatment failures. Vomiting and diarrhoea accounted for 24% of the early failures in children. Patients at increased risk of treatment failure should be monitored closely and given early alternative treatment if fever and parasites persist for > or = 3 d.

The clinical and laboratory features of severe falciparum malaria in 180 Gambian children were studied between 1985 and 1989. Of the 180 children, 118 (66%) presented with seizures, 77 (43%) had cerebral malaria, 35 (20%) had witnessed seizures after admission, 29 (16%) were hypoglycemic, and 27 (15%) died. Respiratory distress was a common harbinger of a fatal outcome. The differences in admission parasite counts in the blood, hematocrit, and opening cerebrospinal pressures for patients who died and survivors were not significant. A multiple logistic regression model identified neurological status (coma, particularly if associated with extensor posturing), stage of parasite development on the peripheral blood film, pulse rate of > 150 or respiratory rate of > 50, hypoglycemia, and hyperlactatemia (plasma lactate level, > 5 mmol/L) as independent indicators of a fatal outcome. Biochemical evidence of hepatic and renal dysfunction was an additional marker of a poor prognosis, but, in contrast to severe malaria in adults, none of these children with severe malaria had acute renal failure.

Fever almost invariably accompanies uncomplicated falciparum malaria. In a randomized, double-'blind' study, we compared a single dose of ibuprofen (10 mg/kg, n = 8) with paracetamol (15 mg/kg, n = 8) for the treatment of fever > 38.5 degrees C due to uncomplicated falciparum malaria. Ibuprofen was significantly more effective than paracetamol in lowering temperatures throughout the first 4.5 h after dosing (P = 0.016) and should be considered as an antipyretic agent in the management of uncomplicated falciparum infections, providing there is no contraindication to its use.

The effects of quinine and paracetamol on fever were studied in 21 adult patients with acute uncomplicated falciparum malaria. Quinine alone (n = 7) had no significant effect on fever, whereas paracetamol given 2 h after quinine (n = 7) or 2 h before quinine (n = 7) reduced temperature by a mean of 2.1 degrees C (standard deviation [SD] 0.95) and 2.1 degrees C (SD 0.79) respectively. A temperature reduction of 1 degree C was associated with a mean decrement of 9.7 beats/min (SD 3.3) in the pulse rate. Quinine does not possess useful antipyretic activity.

Between 1990 and 1994, a series of prospective studies were conducted to optimize the treatment of multidrug-resistant falciparum malaria on the borders of Thailand. The tolerance of various treatment regimens containing either mefloquine 15 mg/kg (M15) or 25 mg/kg (M25) was evaluated in 3673 patients aged between 6 months and 88 years. Early vomiting (within 1 hour) is an important determinant of treatment outcome in these areas, despite re-administration of the dose. Overall, 7 % of the patients vomited within an hour. Significant risk factors were age < or = 6 years (relative risk (RR), 3.9) or > or 50 years (RR, 2.7), the higher mefloquine dose (M25) (RRm 2.7), vomiting < 24 hours before enrolment (RR, 2.5), axillary temperature > 38.0 degrees C (RR, 1.6), and parasitaemia > 10,000/microliter (RR, 1.3). In children < or = 2 years, 30% vomited with M25, and 13% did not tolerate a repeat dose. Vomiting was reduced 40% by splitting the higher dose (RR, 0.6; 95% CI, 0.4-0.8), and 50% by giving mefloquine on the second day in combination with artesunate (RR, 0.5; CI, 0.3-0.9). Anorexia, nausea, vomiting, dizziness, and sleeping disorders were 1.1-1.4 times more frequent with M25 than M15 in the three days following treatment, but were similar in the single or split-dose M25 groups, despite twofold higher mefloquine concentrations obtained with the latter. There was no evidence that diarrhoea, headache, and abdominal pain were associated with mefloquine use. High-dose mefloquine is well tolerated but should be given as a split dose.

Whole blood mefloquine, halofantrine, and desbutyl-halofantrine concentrations were measured by high-performance liquid chromatography in capillary blood, venous blood, and venous plasma samples from patients along the Thai/Burmese border with falciparum malaria who were treated with either mefloquine (25 mg/kg) or halofantrine (24 mg/kg or 72 mg/kg). The limits of detection for mefloquine, halofantrine, and desbutyl-halofantrine were 50, 15, and 10 ng/ml, respectively, with 200 microliters whole blood samples. There was a good linear correlation (r > 0.9) between capillary and venous blood and between whole blood and plasma for all three compounds. Mefloquine concentrations in venous and capillary blood were very similar (mean ratio 1.02, 95% confidence intervals [CI] 0.95-1.09, n = 60), but were 1.15 times higher (95% CI 1.03-1.29) in whole blood than in plasma (n = 22). The halofantrine and desbutyl-halofantrine concentrations were 1.27 (1.12-1.45, n = 23) and 1.34 (1.16-1.55, n = 24) times higher in venous compared to capillary blood, while halofantrine but not desbutyl-halofantrine concentrations were lower in whole blood than in plasma (mean ratios: halofantrine: 0.83 [0.72, 0.94], n = 39 and desbutyl-halofantrine: 1.05 [0.96-1.15], n = 41). Measurement of mefloquine, halofantrine, or desbutyl-halofantrine in capillary blood is an accurate and practical alternative to venous blood sampling, and is particularly useful for sampling with children, and under field conditions when technical facilities are limited.

Studies of 652 adults and children with acute uncomplicated falciparum malaria were done to determine the optimum treatment of multidrug-resistant Plasmodium falciparum malaria on the Thai-Burmese border. Single-dose artesunate (4 mg/kg) plus mefloquine (25 mg of base/kg) gave more rapid symptomatic and parasitologic responses than high-dose mefloquine alone but did not improve cure rates. Three days of artesunate (total dose, 10 mg/kg) plus mefloquine was 98% effective compared with a 28-day failure rate of 31% with high-dose mefloquine alone (relative risk [RR], 0.06; 95% confidence interval [CI], 0.02-0.2; P < .0001). By day 63, the reinfection adjusted failure rates were 2% and 44%, respectively (P < .0001). Artesunate also prevented high-grade failures. Both drugs were well tolerated. No adverse effects were attributable to artesunate. Vomiting was reduced significantly by giving mefloquine on day 2 of treatment (RR, 0.40; 95% CI, 0.20-0.79; P = .009. Artesunate (10 mg/kg over 3 days) plus mefloquine (25 mg/kg) is currently the most effective treatment for falciparum malaria in this area of increasing mefloquine resistance.

The therapeutic efficacy and toxicity of a combination of low dose mefloquine (15 mg/kg) plus artesunate 10 mg/kg in one day (MA) was compared with the currently used regimen of high dose mefloquine (25 mg/kg) (MQ) in 552 patients with uncomplicated falciparum malaria in an area of multi-drug resistance on the Thai-Burmese border. MA gave faster clinical and parasitological responses and prevented early treatment failure; 15 patients in the MQ group (6%) were early failures (< 9 d) compared with none receiving MA (P = 0.0001). Overall failure rates by day 28 were 19% in the MA group and 24% in with MQ group (relative risk (RR) = 0.78, 95% confidence interval (CI) 0.54-1.12). In the subgroup of patients who required re-treatment, MA proved significantly more effective than MQ; failure rates were 25% and 52% respectively (RR = 0.49, 95% CI = 0.29-0.83). Treatment failures were associated with mefloquine treatment in the previous month (RR = 1.72, 95% CI = 1.09-2.70) and diarrhoea (RR = 1.55, 95% CI = 1.05-2.28). Gastrointestinal side-effects and dizziness were more likely in the MQ group. There was no evident adverse effect associated with artesunate. A single day's treatment with artesunate augments the antimalarial efficacy of mefloquine.

Serial clinical and metabolic changes were monitored in 115 Gambian children (1.5-12 years old) with severe malaria. Fifty-three children (46%) had cerebral malaria (coma score < or = 2) and 21 (18%) died. Admission geometric mean venous blood lactate concentrations were almost twice as high in fatal cases as in survivors (7.1 mmol/L vs. 3.6 mmol/L; P < 0.001) and were correlated with levels of tumour necrosis factor (r = 0.42, n = 79; P < 0.0001) and interleukin 1-alpha (r = 0.6, n = 34; P < 0.0001). Admission blood venous glucose concentrations were lower in fatal cases than survivors (3.2 mmol/L, vs. 5.8 mmol/L; P < 0.0001). Treatment with quinine was associated with significantly more episodes of post-admission hypoglycaemia when compared with artemether or chloroquine. After treatment, lactate concentrations fell rapidly in survivors but fell only slightly, or rose, in fatal cases. Plasma cytokine levels fluctuated widely after admission. Sustained hyperlactataemia (raised lactate concentrations, 4 h after admission) proved to be the best overall prognostic indicator of outcome in this series. Lactic acidosis is an important cause of death in severe malaria.

1 The pharmacokinetics, efficacy and toxicity of a new parenteral formulation of halofantrine hydrochloride were evaluated in 12 adults with acute uncomplicated falciparum malaria and nine adults who attended in convalescence. 2 Intravenous halofantrine (1 mg kg(-1) infused in 1 h) was given every 8 h for a total of three doses in the acute study. Halofantrine cleared parasitaemia rapidly in all but one patient, with a mean (s.d.) parasite clearance time of 71 (29) h. Convalescent patients received a single infusion (1 mg kg(-1) in 1 h). 3 An open two-compartment model with the following parameters described the pharmacokinetics of halofantrine in acute malaria (mean (s.d)): V1 = 0.36 (0.18) l kg(-1); CL = 0.355 (0.18) l h(-1) kg(-1); t1/2alpha = 0.19 (0.12) h; t1/2beta = 14.4 (7.5) h. 4 Intravenous halofantrine in acute malaria produced significant prolongations of the QT and QTc intervals (mean (s.d.)) of 20 (15%) and 8.2 (5.6)%, respectively (P < 0.001) after the third dose, but no clinically significant cardiotoxcity. Eight patients experienced mild to moderate thrombophlebitis at the halofantrine infusion site which had resolved in six by the time of follow-up. In the single treatment failure who received oral quinine, there was a large rise in plasma halofantrine concentration but this did not result in detectable toxicity. 5 These data provide the basis for the design of improved dosing regimens for the use of parenteral halofantrine in malaria.

A prospective comparison of the antimalarial efficacy of bed nets was conducted with 341 pregnant women living in a mesoendemic malarious area of the Thai-Burmese border. Women in 3 adjacent study sites were allocated at random to receive either a single size permethrin-impregnated bed net (PIB), a non-impregnated bed net (NIB), or to a control group who used either their own family size non-impregnated bed net (FNIB) or no net. In one study site, but not the other 2, PIB significantly reduced parasite densities and, together with FNIB, reduced the incidence of malaria in pregnancy from 56% to 33% (relative risk = 1.67, confidence interval = 1.07-2.61, P = 0.03, allowing for parity). Anaemia proved a more sensitive marker of bed net antimalarial efficacy than parasite rates. The incidence of anaemia (haematocrit < 30%) at all study sites was significantly lower at delivery in the PIB (27%) and FNIB groups (21%) than in the NIB group (41%) or those using no net (56%). This suggests that a significant proportion of the malaria in pregnancy in this mesoendemic area was sub-patent. Both patent Plasmodium falciparum parasitaemia and anaemia were associated with a reduction in birth weight. Infant mortality was high (16%) and strongly associated with prematurity, low birth weight and maternal anaemia. PIB were well tolerated and had no apparent adverse effect on the pregnancy or infant development. Although the overall effect of bed nets on patent parasitaemia was marginal, they were associated with a significant reduction in maternal malaria-associated anaemia.(ABSTRACT TRUNCATED AT 250 WORDS)

In 1991 and 1992, a prospective randomized trial was conducted on the northern Thai-Cambodian border. That trial compared the efficacy and tolerance of two mefloquine regimens for the treatment of uncomplicated Plasmodium falciparum malaria in an area with multi-drug-resistant P. falciparum. The resolution of fever and other symptoms was faster with high-dose mefloquine (25 mg/kg of body weight [M25 group; n = 68]) than with the conventional 15-mg/kg dose (M15 group; n = 71). There were no early treatment failures (days 7 to 9) in the M25 group, but there were 5 (7%) treatment failures in the M15 group (P = 0.03). The incidences of treatment failures by day 28 were 40% with the M15 group and 11% with the M25 group (P = 0.0004). By day 42, these values had risen to 50 and 27%, respectively (P = 0.01). The risk of treatment failure was highest in children (relative risk, 2.1; 95% confidence interval, 1.3 to 3.4) and patients with posttreatment diarrhea (relative risk, 2.0; 95% confidence interval, 1.3 to 3.1). Over half of the recrudescences in the M25 group occurred between days 28 and 42, whereas 17% of the recrudescences in the M15 group occurred between days 28 and 42 (P = 0.02). Thus, the sensitivity of assessment was significantly increased with longer follow-up. Treatment failure was associated with a delayed parasite clearance and an inadequate hematological recovery. Upper gastrointestinal side effects and dizziness were significantly more common in the M25 group, but overall, the high dose was relatively well tolerated, in particular by children. An increase in the dose to 25 mg/kg can prolong the therapeutic use of mefloquine in areas with multi-drug-resistant P.falciparum malaria where high-grade resistance to mefloquine is still rare.

In a prospective electrocardiographic study of Karen patients with acute uncomplicated falciparum malaria, mefloquine (25 mg/kg) had no cardiac effects (n = 53), but halofantrine (72 mg/kg) induced consistent dose-related lengthening of the PR and QT intervals in all 61 patients treated. The likelihood of significant QTc prolongation (by more than 25% or a QTc of 0.55 s1/2 or more) was greater after halofantrine as retreatment following mefloquine failure than as primary treatment (7/10 vs 18/51; relative risk 2.0 [95% Cl 1.1-3.4], p = 0.04). More than 60% of the effect occurred with three doses of halofantrine (24 mg/kg). The arrhythmogenic potential of halofantrine should now be investigated.

The continuing spread of multidrug resistance in Plasmodium falciparum malaria makes the search for alternative treatments ever more urgent. We have investigated the relative efficacy of halofantrine and mefloquine in two paired randomised trials on the Thai-Burmese border, a multidrug-resistant area. In the first trial, 198 patients with acute uncomplicated falciparum malaria were randomly assigned either the standard halofantrine regimen (24 mg/kg) or mefloquine (25 mg/kg). The cumulative failure rates by day 28 were 35% with halofantrine and 10% with mefloquine (p = 0.0002). In the second study of 437 patients, a higher dose of halofantrine (8 mg/kg every 8 h for 3 days = 72 mg/kg) was both more effective and better tolerated than mefloquine 25 mg/kg; the failure rates were 3% and 8% (p = 0.03), respectively, or 1% vs 6% after adjustment for possible reinfections (p = 0.009). The rate of failure was higher after retreatment than after primary treatment in all study groups. Halofantrine 72 mg/kg was especially effective in the retreatment of these recrudescent infections; the failure rate was 44% with mefloquine and 15% with high-dose halofantrine (relative risk 3.0 [95% CI 1.2-7.3], p = 0.008). Thus, high-dose halofantrine is better tolerated and more effective than mefloquine for the treatment of uncomplicated falciparum malaria in this area. However, evidence of possible cardiotoxicity will need to be investigated fully before a role can be established for halofantrine in the treatment of multidrug-resistant malaria.

The therapeutic efficacy and toxicity of a high-dose (25 mg/kg) mefloquine regimen (M25) and the currently recommended regimen of 15 mg/kg (M15) were compared in 199 patients with acute falciparum malaria in an area with deteriorating multidrug resistance on the Thai-Burmese border. The clinical and parasitologic responses were significantly more rapid with M25. The incidence of treatment failures by day 7-9 was 7% for M15 and 1% for M25 (P = .03) and had increased to 40% and 9%, respectively, by day 28 (P < .0001). Overall failure rates were highest in children (P = .02). Parasite clearance times were a good predictor of the therapeutic response; all patients with parasitemia persisting > 5 days after treatment experienced subsequent recrudescence. Side effects were dose-related and included dizziness, anorexia, nausea, vomiting, and fatigue. Although vomiting < 1 h after treatment was more likely in young children, children overall tolerated mefloquine better than adults, and men better than women. The optimum treatment dose of mefloquine in this area is 25 mg/kg.

A prospective study of malaria during pregnancy was conducted between September 1986 and December 1989 in an area of unstable (mesoendemic) malaria transmission on the Thai-Burmese border. Antenatal clinics were set up in camps for displaced persons of the Karen ethnic minority and 1358 pregnant women were enrolled at a mean estimated gestational age of 23 weeks (standard deviation 5.7 weeks) and were followed weekly until delivery. Malaria developed in 505 women (37.2%); 80.2% of infections were Plasmodium falciparum, 17.1% were P. vivax, and 2.7% were mixed. Primigravidae were infected more commonly than multigravidae: 153/322 (47.5%) compared with 318/953 (33.3%) (P less than 0.001). The incidence of malaria declined from the 20th week of gestation (12%) towards term (4.4%). Most infections were detected before symptoms developed, and there were no deaths associated with malaria. Despite this, malaria was associated with an overall 123 g reduction in birthweight (95% confidence interval [CI] 34-212 g). This reduction was largely accounted for by lower birthweights of babies born to infected primigravidae (mean reduction 151 g, 95% CI 21-282 g) and women in their 2nd and 3rd pregnancies (mean reduction 185 g, 95% CI 84-286 g). The incidence of anaemia requiring treatment was higher in women who developed malaria, 149/420 (35.4%) compared with 191/670 (28.5%), and was proportional to the number of parasitaemic episodes. Thus, despite regular antenatal clinic attendance with prompt detection and treatment of malaria (the currently employed antimalarial strategy in areas with multidrug-resistant P. falciparum), malaria still had a significant adverse effect on pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)