Severe falciparum malaria in pregnancy in Southeast Asia: a multi-centre retrospective cohort study

BACKGROUND

Severe malaria in pregnancy causes maternal mortality, morbidity, and adverse foetal outcomes. The factors contributing to adverse maternal and foetal outcomes are not well defined. We aimed to identify the factors predicting higher maternal mortality and to describe the foetal mortality and morbidity associated with severe falciparum malaria in pregnancy.

METHODS

A retrospective cohort study was conducted of severe falciparum malaria in pregnancy, as defined by the World Health Organization severe malaria criteria. The patients were managed prospectively by the Shoklo Malaria Research Unit (SMRU) on the Thailand-Myanmar border or were included in hospital-based clinical trials in six Southeast Asian countries. Fixed-effects multivariable penalised logistic regression was used for analysing maternal mortality.

RESULTS

We included 213 (123 SMRU and 90 hospital-based) episodes of severe falciparum malaria in pregnancy managed between 1980 and 2020. The mean maternal age was 25.7 (SD 6.8) years, and the mean gestational age was 25.6 (SD 8.9) weeks. The overall maternal mortality was 12.2% (26/213). Coma (adjusted odds ratio [aOR], 7.18, 95% CI 2.01-25.57, p = 0.0002), hypotension (aOR 11.21, 95%CI 1.27-98.92, p = 0.03) and respiratory failure (aOR 4.98, 95%CI 1.13-22.01, p = 0.03) were associated with maternal mortality. Pregnant women with one or more of these three criteria had a mortality of 29.1% (25/86) (95%CI 19.5 to 38.7%) whereas there were no deaths in 88 pregnant women with hyperparasitaemia (> 10% parasitised erythrocytes) only or severe anaemia (haematocrit < 20%) only. In the SMRU prospective cohort, in which the pregnant women were followed up until delivery, the risks of foetal loss (23.3% by Kaplan-Meier estimator, 25/117) and small-for-gestational-age (38.3%, 23/60) after severe malaria were high. Maternal death, foetal loss and preterm birth occurred commonly within a week of diagnosis of severe malaria.

CONCLUSIONS

Vital organ dysfunction in pregnant women with severe malaria was associated with a very high maternal and foetal mortality whereas severe anaemia or hyperparasitaemia alone were not associated with poor prognosis, which may explain the variation of reported mortality from severe malaria in pregnancy. Access to antenatal care must be promoted to reduce barriers to early diagnosis and treatment of both malaria and anaemia.

A molecular barcode and web-based data analysis tool to identify imported Plasmodium vivax malaria

Traditionally, patient travel history has been used to distinguish imported from autochthonous malaria cases, but the dormant liver stages of Plasmodium vivax confound this approach. Molecular tools offer an alternative method to identify, and map imported cases. Using machine learning approaches incorporating hierarchical fixation index and decision tree analyses applied to 799 P. vivax genomes from 21 countries, we identified 33-SNP, 50-SNP and 55-SNP barcodes (GEO33, GEO50 and GEO55), with high capacity to predict the infection's country of origin. The Matthews correlation coefficient (MCC) for an existing, commonly applied 38-SNP barcode (BR38) exceeded 0.80 in 62% countries. The GEO panels outperformed BR38, with median MCCs > 0.80 in 90% countries at GEO33, and 95% at GEO50 and GEO55. An online, open-access, likelihood-based classifier framework was established to support data analysis (vivaxGEN-geo). The SNP selection and classifier methods can be readily amended for other use cases to support malaria control programs.

Investigating causal pathways in severe falciparum malaria: A pooled retrospective analysis of clinical studies

BACKGROUND

Severe falciparum malaria is a medical emergency characterised by potentially lethal vital organ dysfunction. Patient fatality rates even with parenteral artesunate treatment remain high. Despite considerable research into adjuvant therapies targeting organ and tissue dysfunction, none have shown efficacy apart from renal replacement therapy. Understanding the causal contributions of clinical and laboratory abnormalities to mortality is essential for the design and evaluation of novel therapeutic interventions.

METHODS AND FINDINGS

We used a structural model causal inference approach to investigate causal relationships between epidemiological, laboratory, and clinical variables in patients with severe falciparum malaria enrolled in clinical trials and their in-hospital mortality. Under this causal model, we analysed records from 9,040 hospitalised children (0-12 years, n = 5,635) and adults (n = 3,405, 12-87 years) with severe falciparum malaria from 15 countries in Africa and Asia who were studied prospectively over the past 35 years. On admission, patient covariates associated with increased in-hospital mortality were severity of acidosis (odds ratio [OR] 2.10 for a 7-mEq/L increase in base deficit [95% CI 1.93-2.28]), renal impairment (OR 1.71 for a 2-fold increase in blood urea nitrogen [95% CI 1.58, 1.86]), coma (OR 3.59 [95% CI 3.07-4.21]), seizures (OR 1.40 [95% CI 1.16-1.68]), shock (OR 1.51 [95% CI 1.14-1.99]), and presumed pulmonary oedema (OR 1.58 [95% CI 1.04-2.39]). Lower in-hospital mortality was associated with moderate anaemia (OR 0.87 for a decrease of 10 percentage points in haematocrit [95% CI 0.80-0.95]). Circulating parasite density was not associated with mortality (OR 1.02 for a 6-fold increase [95% CI 0.94-1.11]), so the pathological effects of parasitaemia appear to be mediated entirely by the downstream effects of sequestration. Treatment with an artemisinin derivative decreased mortality compared with quinine (OR 0.64 [95% CI 0.56-0.74]). These estimates were consistent across children and adults (mainly representing African and Asian patients, respectively). Using inverse probability weighting, transfusion was not estimated to be beneficial in children with admission haematocrit values between 15% and 25% (OR 0.99 [95% CI 0.97-1.02]). Except for the effects of artemisinin treatment and transfusion, causal interpretations of these estimates could be biased by unmeasured confounding from severe bacterial sepsis, immunity, and duration of illness.

CONCLUSION

These data suggest that moderate anaemia is associated with a reduced risk of death in severe falciparum malaria. This is possibly a direct causal association. The severe anaemia threshold criteria for a definition of severe falciparum malaria should be reconsidered.

The haematological consequences of Plasmodium vivax malaria after chloroquine treatment with and without primaquine: a WorldWide Antimalarial Resistance Network systematic review and individual patient data meta-analysis

BACKGROUND

Malaria causes a reduction in haemoglobin that is compounded by primaquine, particularly in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency. The aim of this study was to determine the relative contributions to red cell loss of malaria and primaquine in patients with uncomplicated Plasmodium vivax.

METHODS

A systematic review identified P. vivax efficacy studies of chloroquine with or without primaquine published between January 2000 and March 2017. Individual patient data were pooled using standardised methodology, and the haematological response versus time was quantified using a multivariable linear mixed effects model with non-linear terms for time. Mean differences in haemoglobin between treatment groups at day of nadir and day 42 were estimated from this model.

RESULTS

In total, 3421 patients from 29 studies were included: 1692 (49.5%) with normal G6PD status, 1701 (49.7%) with unknown status and 28 (0.8%) deficient or borderline individuals. Of 1975 patients treated with chloroquine alone, the mean haemoglobin fell from 12.22 g/dL [95% CI 11.93, 12.50] on day 0 to a nadir of 11.64 g/dL [11.36, 11.93] on day 2, before rising to 12.88 g/dL [12.60, 13.17] on day 42. In comparison to chloroquine alone, the mean haemoglobin in 1446 patients treated with chloroquine plus primaquine was - 0.13 g/dL [- 0.27, 0.01] lower at day of nadir (p = 0.072), but 0.49 g/dL [0.28, 0.69] higher by day 42 (p < 0.001). On day 42, patients with recurrent parasitaemia had a mean haemoglobin concentration - 0.72 g/dL [- 0.90, - 0.54] lower than patients without recurrence (p < 0.001). Seven days after starting primaquine, G6PD normal patients had a 0.3% (1/389) risk of clinically significant haemolysis (fall in haemoglobin > 25% to < 7 g/dL) and a 1% (4/389) risk of a fall in haemoglobin > 5 g/dL.

CONCLUSIONS

Primaquine has the potential to reduce malaria-related anaemia at day 42 and beyond by preventing recurrent parasitaemia. Its widespread implementation will require accurate diagnosis of G6PD deficiency to reduce the risk of drug-induced haemolysis in vulnerable individuals.

TRIAL REGISTRATION

This trial was registered with PROSPERO: CRD42016053312. The date of the first registration was 23 December 2016.

Tafenoquine versus Primaquine to Prevent Relapse of Plasmodium vivax Malaria

BACKGROUND

Tafenoquine, a single-dose therapy for Plasmodium vivax malaria, has been associated with relapse prevention through the clearance of P. vivax parasitemia and hypnozoites, termed "radical cure."

METHODS

We performed a phase 3, prospective, double-blind, double-dummy, randomized, controlled trial to compare tafenoquine with primaquine in terms of safety and efficacy. The trial was conducted at seven hospitals or clinics in Peru, Brazil, Colombia, Vietnam, and Thailand and involved patients with normal glucose-6-phosphate dehydrogenase (G6PD) enzyme activity and female patients with moderate G6PD enzyme deficiency; all patients had confirmed P. vivax parasitemia. The patients were randomly assigned, in a 2:1 ratio, to receive a single 300-mg dose of tafenoquine or 15 mg of primaquine once daily for 14 days (administered under supervision); all patients received a 3-day course of chloroquine and were followed for 180 days. The primary safety outcome was a protocol-defined decrease in the hemoglobin level (>3.0 g per deciliter or ≥30% from baseline or to a level of <6.0 g per deciliter). Freedom from recurrence of P. vivax parasitemia at 6 months was the primary efficacy outcome in a planned patient-level meta-analysis of the current trial and another phase 3 trial of tafenoquine and primaquine (per-protocol populations), and an odds ratio for recurrence of 1.45 (tafenoquine vs. primaquine) was used as a noninferiority margin.

RESULTS

A protocol-defined decrease in the hemoglobin level occurred in 4 of 166 patients (2.4%; 95% confidence interval [CI], 0.9 to 6.0) in the tafenoquine group and in 1 of 85 patients (1.2%; 95% CI, 0.2 to 6.4) in the primaquine group, for a between-group difference of 1.2 percentage points (95% CI, -4.2 to 5.0). In the patient-level meta-analysis, the percentage of patients who were free from recurrence at 6 months was 67.0% (95% CI, 61.0 to 72.3) among the 426 patients in the tafenoquine group and 72.8% (95% CI, 65.6 to 78.8) among the 214 patients in the primaquine group. The efficacy of tafenoquine was not shown to be noninferior to that of primaquine (odds ratio for recurrence, 1.81; 95% CI, 0.82 to 3.96).

CONCLUSIONS

Among patients with normal G6PD enzyme activity, the decline in hemoglobin level with tafenoquine did not differ significantly from that with primaquine. Tafenoquine showed efficacy for the radical cure of P. vivax malaria, although tafenoquine was not shown to be noninferior to primaquine. (Funded by GlaxoSmithKline and Medicines for Malaria Venture; GATHER ClinicalTrials.gov number, NCT02216123 .).

Suboptimal Exposure to Anti-TB Drugs in a TBM/HIV+ Population Is Not Related to Antiretroviral Therapy

A placebo-controlled trial that compares the outcomes of immediate vs. deferred initiation of antiretroviral therapy in HIV +ve tuberculous meningitis (TBM) patients was conducted in Vietnam in 2011. Here, the pharmacokinetics of rifampicin, isoniazid, pyrazinamide, and ethambutol were investigated in the presence and absence of anti-HIV treatment in 85 patients. Pharmacokinetic analyses show that HIV therapy has no significant impact on the pharmacokinetics of TB drugs in this cohort. The same population, however, displayed generally low cerebrospinal fluid (CSF) and systemic exposures to rifampicin compared to previously reported HIV -ve cohorts. Elevated CSF concentrations of pyrazinamide, on the other hand, were strongly and independently correlated with increased mortality and neurological toxicity. The findings suggest that the current standard dosing regimens may put the patient at risk of treatment failure from suboptimal rifampicin exposure, and potentially increasing the risk of adverse central nervous system events that are independently correlated with pyrazinamide CSF exposure.

Optimal health and disease management using spatial uncertainty: a geographic characterization of emergent artemisinin-resistant Plasmodium falciparum distributions in Southeast Asia

BACKGROUND

Artemisinin-resistant Plasmodium falciparum malaria parasites are now present across much of mainland Southeast Asia, where ongoing surveys are measuring and mapping their spatial distribution. These efforts require substantial resources. Here we propose a generic 'smart surveillance' methodology to identify optimal candidate sites for future sampling and thus map the distribution of artemisinin resistance most efficiently.

METHODS

The approach uses the 'uncertainty' map generated iteratively by a geostatistical model to determine optimal locations for subsequent sampling.

RESULTS

The methodology is illustrated using recent data on the prevalence of the K13-propeller polymorphism (a genetic marker of artemisinin resistance) in the Greater Mekong Subregion.

CONCLUSION

This methodology, which has broader application to geostatistical mapping in general, could improve the quality and efficiency of drug resistance mapping and thereby guide practical operations to eliminate malaria in affected areas.

Intensified Antituberculosis Therapy in Adults with Tuberculous Meningitis

BACKGROUND

Tuberculous meningitis is often lethal. Early antituberculosis treatment and adjunctive treatment with glucocorticoids improve survival, but nearly one third of patients with the condition still die. We hypothesized that intensified antituberculosis treatment would enhance the killing of intracerebral Mycobacterium tuberculosis organisms and decrease the rate of death among patients.

METHODS

We performed a randomized, double-blind, placebo-controlled trial involving human immunodeficiency virus (HIV)-infected adults and HIV-uninfected adults with a clinical diagnosis of tuberculous meningitis who were admitted to one of two Vietnamese hospitals. We compared a standard, 9-month antituberculosis regimen (which included 10 mg of rifampin per kilogram of body weight per day) with an intensified regimen that included higher-dose rifampin (15 mg per kilogram per day) and levofloxacin (20 mg per kilogram per day) for the first 8 weeks of treatment. The primary outcome was death by 9 months after randomization.

RESULTS

A total of 817 patients (349 of whom were HIV-infected) were enrolled; 409 were randomly assigned to receive the standard regimen, and 408 were assigned to receive intensified treatment. During the 9 months of follow-up, 113 patients in the intensified-treatment group and 114 patients in the standard-treatment group died (hazard ratio, 0.94; 95% confidence interval, 0.73 to 1.22; P=0.66). There was no evidence of a significant differential effect of intensified treatment in the overall population or in any of the subgroups, with the possible exception of patients infected with isoniazid-resistant M. tuberculosis. There were also no significant differences in secondary outcomes between the treatment groups. The overall number of adverse events leading to treatment interruption did not differ significantly between the treatment groups (64 events in the standard-treatment group and 95 events in the intensified-treatment group, P=0.08).

CONCLUSIONS

Intensified antituberculosis treatment was not associated with a higher rate of survival among patients with tuberculous meningitis than standard treatment. (Funded by the Wellcome Trust and the Li Ka Shing Foundation; Current Controlled Trials number, ISRCTN61649292.).

Arsenic exposure to drinking water in the Mekong Delta

Arsenic (As) contamination of groundwater drinking sources was investigated in the Mekong Delta, Vietnam in order to assess the occurrence of As in the groundwater, and the magnitude of As exposure of local residents through measurements of As in toenails of residents consuming groundwater as their major drinking water source. Groundwater (n=68) and toenail (n=62) samples were collected in Dong Thap Province, adjacent to the Mekong River, in southern Vietnam. Fifty-three percent (n=36) of the wells tested had As content above the World Health Organization's (WHO) recommended limit of 10 ppb. Samples were divided into Northern (mean As=4.0 ppb) and Southern (329.0 ppb) groups; wells from the Southern group were located closer to the Mekong River. Elevated As contents were associated with depth (<200 m), salinity (low salinity), and redox state (reducing conditions) of the study groundwater. In 79% of the wells, As was primarily composed of the reduced As(III) species. Arsenic content in nails collected from local residents was significantly correlated to As in drinking water (r=0.49, p<0.001), and the relationship improved for pairs in which As in drinking water was higher than 1 ppb (r=0.56, p<0.001). Survey data show that the ratio of As in nail to As in water varied among residents, reflecting differential As bioaccumulation in specific exposed sub-populations. The data show that water filtration and diet, particularly increased consumption of animal protein and dairy, and reduced consumption of seafood, were associated with lower ratios of As in nail to As in water and thus could play important roles in mitigating As exposure in areas where As-rich groundwater is the primary drinking water source.

Assessment of therapeutic responses to gametocytocidal drugs in Plasmodium falciparum malaria

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.

Optimal sampling designs for estimation of Plasmodium falciparum clearance rates in patients treated with artemisinin derivatives

BACKGROUND

The emergence of Plasmodium falciparum resistance to artemisinins in Southeast Asia threatens the control of malaria worldwide. The pharmacodynamic hallmark of artemisinin derivatives is rapid parasite clearance (a short parasite half-life), therefore, the in vivo phenotype of slow clearance defines the reduced susceptibility to the drug. Measurement of parasite counts every six hours during the first three days after treatment have been recommended to measure the parasite clearance half-life, but it remains unclear whether simpler sampling intervals and frequencies might also be sufficient to reliably estimate this parameter.

METHODS

A total of 2,746 parasite density-time profiles were selected from 13 clinical trials in Thailand, Cambodia, Mali, Vietnam, and Kenya. In these studies, parasite densities were measured every six hours until negative after treatment with an artemisinin derivative (alone or in combination with a partner drug). The WWARN Parasite Clearance Estimator (PCE) tool was used to estimate "reference" half-lives from these six-hourly measurements. The effect of four alternative sampling schedules on half-life estimation was investigated, and compared to the reference half-life (time zero, 6, 12, 24 (A1); zero, 6, 18, 24 (A2); zero, 12, 18, 24 (A3) or zero, 12, 24 (A4) hours and then every 12 hours). Statistical bootstrap methods were used to estimate the sampling distribution of half-lives for parasite populations with different geometric mean half-lives. A simulation study was performed to investigate a suite of 16 potential alternative schedules and half-life estimates generated by each of the schedules were compared to the "true" half-life. The candidate schedules in the simulation study included (among others) six-hourly sampling, schedule A1, schedule A4, and a convenience sampling schedule at six, seven, 24, 25, 48 and 49 hours.

RESULTS

The median (range) parasite half-life for all clinical studies combined was 3.1 (0.7-12.9) hours. Schedule A1 consistently performed the best, and schedule A4 the worst, both for the individual patient estimates and for the populations generated with the bootstrapping algorithm. In both cases, the differences between the reference and alternative schedules decreased as half-life increased. In the simulation study, 24-hourly sampling performed the worst, and six-hourly sampling the best. The simulation study confirmed that more dense parasite sampling schedules are required to accurately estimate half-life for profiles with short half-life (≤ three hours) and/or low initial parasite density (≤ 10,000 per μL). Among schedules in the simulation study with six or fewer measurements in the first 48 hours, a schedule with measurements at times (time windows) of 0 (0-2), 6 (4-8), 12 (10-14), 24 (22-26), 36 (34-36) and 48 (46-50) hours, or at times 6, 7 (two samples in time window 5-8), 24, 25 (two samples during time 23-26), and 48, 49 (two samples during time 47-50) hours, until negative most accurately estimated the "true" half-life. For a given schedule, continuing sampling after two days had little effect on the estimation of half-life, provided that adequate sampling was performed in the first two days and the half-life was less than three hours. If the measured parasitaemia at two days exceeded 1,000 per μL, continued sampling for at least once a day was needed for accurate half-life estimates.

CONCLUSIONS

This study has revealed important insights on sampling schedules for accurate and reliable estimation of Plasmodium falciparum half-life following treatment with an artemisinin derivative (alone or in combination with a partner drug). Accurate measurement of short half-lives (rapid clearance) requires more dense sampling schedules (with more than twice daily sampling). A more intensive sampling schedule is, therefore, recommended in locations where P. falciparum susceptibility to artemisinins is not known and the necessary resources are available. Counting parasite density at six hours is important, and less frequent sampling is satisfactory for estimating long parasite half-lives in areas where artemisinin resistance is present.

Combination antifungal therapy for cryptococcal meningitis

BACKGROUND

Combination antifungal therapy (amphotericin B deoxycholate and flucytosine) is the recommended treatment for cryptococcal meningitis but has not been shown to reduce mortality, as compared with amphotericin B alone. We performed a randomized, controlled trial to determine whether combining flucytosine or high-dose fluconazole with high-dose amphotericin B improved survival at 14 and 70 days.

METHODS

We conducted a randomized, three-group, open-label trial of induction therapy for cryptococcal meningitis in patients with human immunodeficiency virus infection. All patients received amphotericin B at a dose of 1 mg per kilogram of body weight per day; patients in group 1 were treated for 4 weeks, and those in groups 2 and 3 for 2 weeks. Patients in group 2 concurrently received flucytosine at a dose of 100 mg per kilogram per day for 2 weeks, and those in group 3 concurrently received fluconazole at a dose of 400 mg twice daily for 2 weeks.

RESULTS

A total of 299 patients were enrolled. Fewer deaths occurred by days 14 and 70 among patients receiving amphotericin B and flucytosine than among those receiving amphotericin B alone (15 vs. 25 deaths by day 14; hazard ratio, 0.57; 95% confidence interval [CI], 0.30 to 1.08; unadjusted P=0.08; and 30 vs. 44 deaths by day 70; hazard ratio, 0.61; 95% CI, 0.39 to 0.97; unadjusted P=0.04). Combination therapy with fluconazole had no significant effect on survival, as compared with monotherapy (hazard ratio for death by 14 days, 0.78; 95% CI, 0.44 to 1.41; P=0.42; hazard ratio for death by 70 days, 0.71; 95% CI, 0.45 to 1.11; P=0.13). Amphotericin B plus flucytosine was associated with significantly increased rates of yeast clearance from cerebrospinal fluid (-0.42 log10 colony-forming units [CFU] per milliliter per day vs. -0.31 and -0.32 log10 CFU per milliliter per day in groups 1 and 3, respectively; P<0.001 for both comparisons). Rates of adverse events were similar in all groups, although neutropenia was more frequent in patients receiving a combination therapy.

CONCLUSIONS

Amphotericin B plus flucytosine, as compared with amphotericin B alone, is associated with improved survival among patients with cryptococcal meningitis. A survival benefit of amphotericin B plus fluconazole was not found. (Funded by the Wellcome Trust and the British Infection Society; Controlled-Trials.com number, ISRCTN95123928.).

Effects of short-course oral corticosteroid therapy in early dengue infection in Vietnamese patients: a randomized, placebo-controlled trial

BACKGROUND

Patients with dengue can experience a variety of serious complications including hypovolemic shock, thrombocytopenia, and bleeding. These problems occur as plasma viremia is resolving and are thought to be immunologically mediated. Early corticosteroid therapy may prevent the development of such complications but could also prolong viral clearance.

METHODS

We performed a randomized, placebo-controlled, blinded trial of low-dose (0.5 mg/kg) or high-dose (2 mg/kg) oral prednisolone therapy for 3 days in Vietnamese patients aged 5-20 years admitted with dengue and fever for ≤72 hours, aiming to assess potential harms from steroid use during the viremic phase. Intention-to-treat analysis was performed using linear trend tests with a range of clinical and virological endpoints specified in advance. In addition to recognized complications of dengue, we focused on the are under the curve for serial plasma viremia measurements and the number of days after enrollment to negative viremia and dengue nonstructural protein 1 status.

RESULTS

Between August 2009 and January 2011, 225 participants were randomized to 1 of the 3 treatment arms. Baseline characteristics were similar across the groups. All patients recovered fully and adverse events were infrequent. Aside from a trend toward hyperglycemia in the steroid recipients, we found no association between treatment allocation and any of the predefined clinical, hematological, or virological endpoints.

CONCLUSIONS

Use of oral prednisolone during the early acute phase of dengue infection was not associated with prolongation of viremia or other adverse effects. Although not powered to assess efficacy, we found no reduction in the development of shock or other recognized complications of dengue virus infection in this study.

Coma in fatal adult human malaria is not caused by cerebral oedema

BACKGROUND

The role of brain oedema in the pathophysiology of cerebral malaria is controversial. Coma associated with severe Plasmodium falciparum malaria is multifactorial, but associated with histological evidence of parasitized erythrocyte sequestration and resultant microvascular congestion in cerebral vessels. To determine whether these changes cause breakdown of the blood-brain barrier and resultant perivascular or parenchymal cerebral oedema, histology, immunohistochemistry and image analysis were used to define the prevalence of histological patterns of oedema and the expression of specific molecular pathways involved in water balance in the brain in adults with fatal falciparum malaria.

METHODS

The brains of 20 adult Vietnamese patients who died of severe malaria were examined for evidence of disrupted vascular integrity. Immunohistochemistry and image analysis was performed on brainstem sections for activation of the vascular endothelial growth factor (VEGF) receptor 2 and expression of the aquaporin 4 (AQP4) water channel protein. Fibrinogen immunostaining was assessed as evidence of blood-brain barrier leakage and perivascular oedema formation. Correlations were performed with clinical, biochemical and neuropathological parameters of severe malaria infection.

RESULTS

The presence of oedema, plasma protein leakage and evidence of VEGF signalling were heterogeneous in fatal falciparum malaria and did not correlate with pre-mortem coma. Differences in vascular integrity were observed between brain regions with the greatest prevalence of disruption in the brainstem, compared to the cortex or midbrain. There was a statistically non-significant trend towards higher AQP4 staining in the brainstem of cases that presented with coma (P = .02).

CONCLUSIONS

Histological evidence of cerebral oedema or immunohistochemical evidence of localised loss of vascular integrity did not correlate with the occurrence of pre-mortem coma in adults with fatal falciparum malaria. Enhanced expression of AQP4 water channels in the brainstem may, therefore, reflect a mix of both neuropathological or attempted neuroprotective responses to oedema formation.

Multicentre prospective study on dengue classification in four South-east Asian and three Latin American countries

OBJECTIVE

To evaluate the existing WHO dengue classification across all age groups and a wide geographical range and to develop a revised evidence-based classification that would better reflect clinical severity.

METHODS

We followed suspected dengue cases daily in seven countries across South-east Asia and Latin America and then categorised them into one of three intervention groups describing disease severity according to the overall level of medical and nursing support required. Using a pre-defined analysis plan, we explored the clinical and laboratory profiles characteristic of these intervention categories and presented the most promising options for a revised classification scheme to an independent group of WHO dengue experts for consideration. Potential warning signs were also evaluated by comparing contemporaneous data of patients who progressed to severe disease with the data of those who did not.

RESULTS

A total of 2259 patients were recruited during 2006-2007 and 230 (13%) of the 1734 laboratory-confirmed patients required major intervention. Applying the existing WHO system, 47/210 (22%) of patients with shock did not fulfil all the criteria for dengue haemorrhagic fever. However, no three-tier revision adequately described the different severity groups either. Inclusion of readily discernible complications (shock/severe vascular leakage and/or severe bleeding and/or severe organ dysfunction) was necessary to devise a system that identified patients requiring major intervention with sufficient sensitivity and specificity to be practically useful. Only a small number of subjects (5%) progressed to severe disease while under observation; several warning signs were identified, but much larger studies are necessary to fully characterize features associated with disease progression.

CONCLUSIONS

Based on these results, a revised classification system comprised of two entities, 'Dengue' and 'Severe Dengue', was proposed and has now been incorporated into the new WHO guidelines.

Usefulness and applicability of the revised dengue case classification by disease: multi-centre study in 18 countries

Background

In view of the long term discussion on the appropriateness of the dengue classification into dengue fever (DF), dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS), the World Health Organization (WHO) has outlined in its new global dengue guidelines a revised classification into levels of severity: dengue fever with an intermediary group of "dengue fever with warning sings", and severe dengue. The objective of this paper was to compare the two classification systems regarding applicability in clinical practice and surveillance, as well as user-friendliness and acceptance by health staff.

Methods

A mix of quantitative (prospective and retrospective review of medical charts by expert reviewers, formal staff interviews), semi-quantitative (open questions in staff interviews) and qualitative methods (focus group discussions) were used in 18 countries. Quality control of data collected was undertaken by external monitors.

Results

The applicability of the DF/DHF/DSS classification was limited, even when strict DHF criteria were not applied (13.7% of dengue cases could not be classified using the DF/DHF/DSS classification by experienced reviewers, compared to only 1.6% with the revised classification). The fact that some severe dengue cases could not be classified in the DF/DHF/DSS system was of particular concern. Both acceptance and perceived user-friendliness of the revised system were high, particularly in relation to triage and case management. The applicability of the revised classification to retrospective data sets (of importance for dengue surveillance) was also favourable. However, the need for training, dissemination and further research on the warning signs was highlighted.

Conclusions

The revised dengue classification has a high potential for facilitating dengue case management and surveillance.

The antimicrobial resistance patterns and associated determinants in Streptococcus suis isolated from humans in southern Vietnam, 1997-2008

Background

Streptococcus suis is an emerging zoonotic pathogen and is the leading cause of bacterial meningitis in adults in Vietnam. Systematic data on the antimicrobial susceptibility profiles of S. suis strains isolated from human cases are lacking. We studied antimicrobial resistance and associated resistance determinants in S. suis isolated from patients with meningitis in southern Vietnam.

Methods

S. suis strains isolated between 1997 and 2008 were investigated for their susceptibility to six antimicrobial agents. Strains were screened for the presence and expression of tetracycline and erythromycin resistance determinants and the association of tet(M) genes with Tn916- like transposons. The localization of tetracycline resistance gene tet(L) was determined by pulse field gel electrophoresis and Southern blotting.

Results

We observed a significant increase in resistance to tetracycline and chloramphenicol, which was concurrent with an increase in multi-drug resistance. In tetracycline resistance strains, we identified tet(M), tet(O), tet(W) and tet(L) and confirmed their expression. All tet(M) genes were associated with a Tn916-like transposon. The co-expression of tet(L) and other tetracycline resistance gene(s) encoding for ribosomal protection protein(s) was only detected in strains with a minimum inhibitory concentration (MIC) of tetracycline of ≥ 64 mg/L

Conclusions

We demonstrated that multi-drug resistance in S. suis causing disease in humans in southern Vietnam has increased over the 11-year period studied. We report the presence and expression of tet(L) in S. suis strains and our data suggest that co-expression of multiple genes encoding distinct mechanism is required for an MIC ≥ 64 mg/L to tetracycline.

A prospective descriptive study of cryptococcal meningitis in HIV uninfected patients in Vietnam - high prevalence of Cryptococcus neoformans var grubii in the absence of underlying disease

Background

Most cases of cryptococcal meningitis occur in patients with HIV infection: the course and outcome of disease in the apparently immunocompetent is much more poorly understood. We describe a cohort of HIV uninfected Vietnamese patients with cryptococcal meningitis in whom underlying disease is uncommon, and relate presenting features of patients and the characteristics of the infecting species to outcome.

Methods

A prospective descriptive study of HIV negative patients with cryptococcal meningitis based at the Hospital for Tropical Diseases, Ho Chi Minh City. All patients had comprehensive clinical assessment at baseline, were cared for by a dedicated study team, and were followed up for 2 years. Clinical presentation was compared by infecting isolate and outcome.

Results

57 patients were studied. Cryptococcus neoformans var grubii molecular type VN1 caused 70% of infections; C. gattii accounted for the rest. Most patients did not have underlying disease (81%), and the rate of underlying disease did not differ by infecting species. 11 patients died while in-patients (19.3%). Independent predictors of death were age ≥ 60 years and a history of convulsions (odds ratios and 95% confidence intervals 8.7 (1 - 76), and 16.1 (1.6 - 161) respectively). Residual visual impairment was common, affecting 25 of 46 survivors (54.3%). Infecting species did not influence clinical phenotype or outcome. The minimum inhibitory concentrations of flucytosine and amphotericin B were significantly higher for C. neoformans var grubii compared with C. gattii (p < 0.001 and p = 0.01 respectively).

Conclusion

In HIV uninfected individuals in Vietnam, cryptococcal meningitis occurs predominantly in people with no clear predisposing factor and is most commonly due to C. neoformans var grubii. The rates of mortality and visual loss are high and independent of infecting species. There are detectable differences in susceptibility to commonly used antifungal drugs between species, but the clinical significance of this is not clear.

Randomized controlled trial of artesunate or artemether in Vietnamese adults with severe falciparum malaria

Background

Both artemether and artesunate have been shown to be superior to quinine for the treatment of severe falciparum malaria in Southeast Asian adults, although the magnitude of the superiority has been greater for artesunate than artemether. These two artemisinin derivatives had not been compared in a randomized trial.

Methods

A randomized double blind trial in 370 adults with severe falciparum malaria; 186 received intramuscular artesunate (2.4 mg/kg immediately followed by 1.2 mg/kg at 12 hours then 24 hours then daily) and 184 received intramuscular artemether (3.6 mg per kilogram immediately followed by 1.8 mg per kilogram daily) was conducted in Viet Nam. Both drugs were given for a minimum of 72 hours.

Results

There were 13 deaths in the artesunate group (7 percent) and 24 in the artemether group (13 percent); P = 0.052; relative risk of death in the patients given artesunate, 0.54; (95 percent confidence interval 0.28-1.02). Parasitaemia declined more rapidly in the artesunate group. Both drugs were very well tolerated.

Conclusions

Intramuscular artesunate may be superior to intramuscular artemether for the treatment of severe malaria in adults.

Avian influenza--a review for doctors in travel medicine

First identified in humans in Hong Kong, influenza A/H5N1, known commonly as avian influenza, has caused human disease in 15 countries around the world. Although the current number of confirmed patients is tiny compared to seasonal and the recently emerged H1N1 'swine' influenza, H5N1 remains a candidate for the next highly pathogenic influenza pandemic. Currently, H5N1 has very limited ability to spread from person-to-person but this may change because of mutation or reassortment with other influenza viruses leading to an influenza pandemic with high mortality. If this occurs travellers are likely to be affected and travel medicine doctors will need to consider avian influenza in returning febrile travellers. The early clinical features may be dismissed easily as 'the flu' resulting in delayed treatment. Treatment options are limited. Oral oseltamivir alone has been the most commonly used drug but mortality remains substantial, up to 80% in Indonesia. Intravenous peramivir has been filed for registration and IV zanamivir is being developed. This review will focus on the epidemiological and clinical features of influenza A/H5N1 avian influenza and will highlight aspects relevant to travel medicine doctors.

Reduced helminth burden increases allergen skin sensitization but not clinical allergy: a randomized, double-blind, placebo-controlled trial in Vietnam

BACKGROUND

Observational evidence suggests that infection with helminths protects against allergic disease and allergen skin sensitization. It is postulated that such effects are mediated by helminth-induced cytokine responses, in particular IL-10.

OBJECTIVE

We tested this hypothesis in a rural area of central Vietnam where hookworm infection is endemic.

METHODS

One thousand five hundred and sixty-six schoolchildren aged 6-17 were randomly allocated to receive either anti-helminthic therapy or a placebo at 0, 3, 6, and 9 months. We compared changes in the prevalence of exercise-induced bronchoconstriction, allergen skin sensitization, flexural eczema on skin examination, questionnaire-reported allergic disease (wheeze and rhinitis symptoms), and immunological parameters (hookworm-induced IFN-gamma, IL-5, IL-10) between 0 and 12 months.

RESULTS

One thousand four hundred and eighty-seven children (95% of these randomized) completed the study. The most common helminth infections were hookworm (65%) and Ascaris lumbricoides (7%). There was no effect of the therapy on the primary outcome, exercise-induced bronchoconstriction (within-participant mean percent fall in peak flow from baseline after anti-helminthic treatment 2.25 (SD 7.3) vs. placebo 2.19 (SD 7.8, P=0.9), or on the prevalence of questionnaire-reported wheeze [adjusted odds ratio (OR)=1.16, 95% confidence interval (CI) 0.35-3.82, P=0.8] and rhinitis (adjusted OR=1.39, 0.89-2.15, P=0.1), or flexural dermatitis on skin examination (adjusted OR=1.15, 0.39-3.45, P=0.8). However, anti-helminthic therapy was associated with a significantly higher allergen skin sensitization risk (adjusted OR=1.31, 1.02-1.67, P=0.03). This effect was particularly strong for children infected with A. lumbricoides at baseline (adjusted OR=4.90, 1.48-16.19, P=0.009). Allergen skin sensitization was inversely related to hookworm-specific IL-10 at baseline (adjusted OR=0.76, 0.59-0.99, P=0.04). No cytokine tested, including IL-10, changed significantly after the anti-helminthic therapy compared with the placebo.

CONCLUSION

A significant reduction in worm burden over a 12-month period in helminth-infected children increases the risk of allergen skin sensitization but not of clinical allergic disease. The effect on skin sensitization could not be fully explained by any of the immunological parameters tested.

Quantification of artemisinin in human plasma using liquid chromatography coupled to tandem mass spectrometry

A liquid chromatographic tandem mass spectroscopy method for the quantification of artemisinin in human heparinised plasma has been developed and validated. The method uses Oasis HLB mu-elution solid phase extraction 96-well plates to facilitate a high throughput of 192 samples a day. Artesunate (internal standard) in a plasma-water solution was added to plasma (50 microL) before solid phase extraction. Artemisinin and its internal standard artesunate were analysed by liquid chromatography and MS/MS detection on a Hypersil Gold C18 (100 mm x 2.1 mm, 5 microm) column using a mobile phase containing acetonitrile-ammonium acetate 10mM pH 3.5 (50:50, v/v) at a flow rate of 0.5 mL/min. The method has been validated according to published FDA guidelines and showed excellent performance. The within-day, between-day and total precisions expressed as R.S.D., were lower than 8% at all tested quality control levels including the upper and lower limit of quantification. The limit of detection was 0.257 ng/mL for artemisinin and the calibration range was 1.03-762 ng/mL using 50 microL plasma. The method was free from matrix effects as demonstrated both graphically and quantitatively.

A common human TLR1 polymorphism regulates the innate immune response to lipopeptides

Toll-like receptors (TLR) are critical mediators of the immune response to pathogens and human polymorphisms in this gene family regulate inflammatory pathways and are associated with susceptibility to infection. Lipopeptides are present in a wide variety of microbes and stimulate immune responses through TLR1/2 or TLR2/6 heterodimers. It is not currently known whether polymorphisms in TLR1 regulate the innate immune response. We stimulated human whole blood with triacylated lipopeptide, a ligand for TLR1/2 heterodimers, and found substantial inter-individual variation in the immune response. We sequenced the coding region of TLR1 and found a non-synonymous polymorphism, I602S (base pair T1805G), that regulated signalling. In comparison to TLR1_602S, the 602I variant mediated substantially greater basal and lipopeptide-induced NF-kappaB signalling in transfected HEK293 cells. These signalling differences among TLR1 variants were also found with stimulation by extracts of Mycobacterium tuberculosis. Furthermore, individuals with the 602II genotype produced substantially more IL-6 than those with the 602SS variant in a lipopeptide-stimulated whole-blood cytokine assay. Together, these observations demonstrate that variation in the inflammatory response to bacterial lipopeptides is regulated by a common TLR1 transmembrane domain polymorphism that could potentially impact the innate immune response and clinical susceptibility to a wide spectrum of pathogens.

A polymorphism in human TLR2 is associated with increased susceptibility to tuberculous meningitis

Tuberculous meningitis (TBM) results from the haematogenous dissemination of Mycobacterium tuberculosis from the lung to the brain. Dissemination is believed to occur early during infection, before the development of adaptive immunity. Toll-like receptor 2 (TLR2) mediates recognition of M. tuberculosis and initiates the innate immune response to infection. We hypothesized that polymorphisms in the TLR2 gene influence bacterial dissemination and the development of TBM. A case-control study was designed to test the hypothesis. Cases of bacteriologically confirmed pulmonary tuberculosis (TB) (n=183) and TBM (n=175), and cord blood controls (n=389) were enrolled in Vietnam. TLR2 genotype 597CC was associated with susceptibility to TB (odds ratio (OR)=2.22, 95% confidence interval (CI): 1.23-3.99). The association was found with meningeal rather than pulmonary TB (TBM vs control, OR=3.26, 95% CI: 1.72-6.18), and was strongest when miliary TB was found on chest radiography (controls vs TBM with miliary TB, OR=5.28, 95% CI: 2.20-12.65). Furthermore, the association increased with the severity of neurologic symptoms (grade I TBM, OR=1.93, 95% CI: 0.54-6.92; grade II, OR=3.32, 95% CI: 0.84-13.2; and grade III, OR=5.70, 95% CI: 1.81-18.0). These results demonstrate a strong association of TLR2 SNP T597C with the development of TBM and miliary TB and indicate that TLR2 influences the dissemination of M. tuberculosis.

The radiologic manifestations of H5N1 avian influenza

Avian influenza is caused by the H5N1 subtype of the influenza A virus. Human transmission is either directly through close contact with infected birds usually poultry or their secretions. To date 178 people throughout South East Asia have been infected with 85 deaths. Patients usually present with a rapidly progressive pneumonia that can result in respiratory failure and acute respiratory distress syndrome. The chest radiograph therefore remains the most convenient and accessible imaging modality. Studies have shown that most radiographs are abnormal at the time of presentation with multifocal consolidation the commonest radiographic finding. During the course of disease, pleural effusions and cavitation can also develop. Consolidation that involves > or = 4 zones on presentation or at day 7 after the onset of symptoms and subsequent development of acute respiratory distress syndrome are generally associated with an adverse outcome. Chest CT examinations performed during the convalescent period have demonstrated persistent ground glass attenuation and segmental consolidation. Additional features included pseudocavitation, pneumatocoele formation, lymphadenopathy, and centrilobular nodules. Overall the appearances are suggestive of mild fibrosis.

Cerebral calpain in fatal falciparum malaria

Disruption of axonal transport may represent a final common pathway leading to neurological dysfunction in cerebral malaria (CM). Calpains are calcium (Ca2+)-activated cysteine proteases which have been implicated in axonal injury in neurological diseases of various aetiologies. In this study we examined the association between mu- and m-calpain, the specific inhibitor calpastatin, and axonal injury in post mortem brain tissue from patients who died from severe malaria. Calpains were associated with axons labelled for the beta-amyloid precursor protein that detects impaired axonal transport. Elevated levels of calpastatin were rarely observed in injured axons. There were increased numbers of neurones with mu-calpain in the nuclear compartment in severe malaria cases compared with non-neurological controls, and increased numbers of glia with nuclear mu-calpain in CM patients compared with non-CM malaria cases and non-neurological controls. There was marked redistribution of calpastatin in the sequestered Plasmodium falciparum-infected erythrocytes. Responses specific to malaria infection were ascertained following analysis of brain samples from fatal cases with acute axonal injury, HIV encephalitis, and progressive multifocal leucoencephalopathy. Our findings implicate a role for calpains in the modulation of disease progression in CM.

A simple and rapid liquid chromatographic assay for evaluation of potentially counterfeit Tamiflu

A simple and rapid liquid chromatographic assay for the evaluation of potentially counterfeit oseltamivir (Tamiflu has been developed and assessed. The assay uses approximately 1mg Tamiflu powder when used for authentication and content estimate. The procedure was validated using 50 replicates analysed during five independent series with a total R.S.D. of 11.2%. The assay can also be used to monitor the exact content of oseltamivir in Tamiflu capsules. One Tamiflu capsule was transferred to a 250mL volumetric flask and 150mL water was added. The flask was placed in an ultrasonic bath at 40 degrees C for 20min to dissolve the capsule. The solution was allowed to cool to room temperature before the flask was filled up to the mark (250mL). A small aliquot was centrifuged and then directly injected into the LC-system for quantification. Oseltamivir was analysed by liquid chromatography with UV detection on a Hypersil Gold column (150mmx4.6mm) using a mobile phase containing methanol-phosphate buffer (pH 2.5; 0.1M) (50:50, v/v) at a flow rate of 1.0mL/min. The assay was implemented for the analysis of Tamiflu purchased over the Internet and at local pharmacies in Thailand and Vietnam.

Evolution and adaptation of H5N1 influenza virus in avian and human hosts in Indonesia and Vietnam

Highly pathogenic avian influenza virus H5N1 is endemic in poultry in East and Southeast Asia with disease outbreaks recently spreading to parts of central Asia, Europe and Africa. Continued interspecies transmission to humans has been reported in Vietnam, Thailand, Cambodia, Indonesia and China, causing pandemic concern. Here, we genetically characterize 82 H5N1 viruses isolated from poultry throughout Indonesia and Vietnam and 11 human isolates from southern Vietnam together with sequence data available in public databases to address questions relevant to virus introduction, endemicity and evolution. Phylogenetic analysis shows that all viruses from Indonesia form a distinct sublineage of H5N1 genotype Z viruses suggesting this outbreak likely originated from a single introduction that spread throughout the country during the past two years. Continued virus activities in Indonesia were attributed to transmission via poultry movement within the country rather than through repeated introductions by bird migration. Within Indonesia and Vietnam, H5N1 viruses have evolved over time into geographically distinct groups within each country. Molecular analysis of the H5N1 genotype Z genome shows that only the M2 and PB1-F2 genes were under positive selection, suggesting that these genes might be involved in adaptation of this virus to new hosts following interspecies transmission. At the amino acid level 12 residues were under positive selection in those genotype Z viruses, in the HA and PB1-F2 proteins. Some of these residues were more frequently observed in human isolates than in avian isolates and are related to viral antigenicity and receptor binding. Our study provides insight into the ongoing evolution of H5N1 influenza viruses that are transmitting in diverse avian species and at the interface between avian and human hosts.

Analysis of the hypervariable region of the Salmonella enterica genome associated with tRNA(leuX)

The divergence of Salmonella enterica and Escherichia coli is estimated to have occurred approximately 140 million years ago. Despite this evolutionary distance, the genomes of these two species still share extensive synteny and homology. However, there are significant differences between the two species in terms of genes putatively acquired via various horizontal transfer events. Here we report on the composition and distribution across the Salmonella genus of a chromosomal region designated SPI-10 in Salmonella enterica serovar Typhi and located adjacent to tRNA(leuX). We find that across the Salmonella genus the tRNA(leuX) region is a hypervariable hot spot for horizontal gene transfer; different isolates from the same S. enterica serovar can exhibit significant variation in this region. Many P4 phage, plasmid, and transposable element-associated genes are found adjacent to tRNA(leuX) in both Salmonella and E. coli, suggesting that these mobile genetic elements have played a major role in driving the variability of this region.

Fatal Plasmodium falciparum malaria causes specific patterns of splenic architectural disorganization

The spleen is critical for host defense against pathogens, including Plasmodium falciparum. It has a dual role, not only removing aged or antigenically altered erythrocytes from the blood but also as the major lymphoid organ for blood-borne or systemic infections. The human malaria parasite P. falciparum replicates within erythrocytes during asexual blood stages and causes repeated infections that can be associated with severe disease. In spite of the crucial role of the spleen in the innate and acquired immune response to malaria, there is little information on the pathology of the spleen in human malaria. We performed a histological and quantitative immunohistochemical study of spleen sections from Vietnamese adults dying from severe falciparum malaria and compared the findings with the findings for spleen sections from control patients and patients dying from systemic bacterial sepsis. Here we report that the white pulp in the spleens of patients dying from malaria showed a marked architectural disorganization. We observed a marked dissolution of the marginal zones with relative loss of B cells. Furthermore, we found strong HLA-DR expression on sinusoidal lining cells but downregulation on cordal macrophages. P. falciparum infection results in alterations in splenic leukocytes, many of which are not seen in sepsis.

Fake antimalarials in Southeast Asia are a major impediment to malaria control: multinational cross-sectional survey on the prevalence of fake antimalarials

OBJECTIVE

To assess the prevalence of counterfeit antimalarial drugs in Southeast (SE) Asia.

DESIGN

Cross-sectional survey.

SETTING

Pharmacies and shops selling antimalarial drugs in Myanmar (Burma), Lao PDR, Vietnam, Cambodia and Thailand.

MAIN OUTCOME MEASURES

Proportion of artemisinin derivatives or mefloquine containing drugs of substandard quality.

RESULTS

Of the 188 tablet packs purchased which were labelled as 'artesunate' 53% did not contain any artesunate. All counterfeit artesunate tablets were labelled as manufactured by 'Guilin Pharma', and refinements of the fake blisterpacks made them often hard to distinguish from their genuine counterparts. No other artemisinin derivatives were found to be counterfeited. Of the 44 mefloquine samples, 9% contained <10% of the expected amount of active ingredient.

CONCLUSIONS

An alarmingly high proportion of antimalarial drugs bought in pharmacies and shops in mainland SE Asia are counterfeit, and the problem has increased significantly compared with our previous survey in 1999-2000. This is a serious threat to public health in the region.

Comparative pharmacokinetics of intramuscular artesunate and artemether in patients with severe falciparum malaria

The first-dose pharmacokinetic properties of intramuscular (i.m.) artesunate (ARTS; 2.4 mg/kg immediately [stat], followed by 1.2 mg/kg i.m. daily) and artemether (ARM; 3.2 mg/kg i.m. stat, followed by 1.6 mg/kg i.m. daily) were compared in Vietnamese adults with severe falciparum malaria. A total of 19 patients were studied; 9 received ARTS, and 10 received ARM. ARTS was absorbed very rapidly; concentrations in plasma peaked between 1,362 and 8,388 nmol/liter (median, 5,710 nmol/liter) within 20 min of injection and then declined with a median (range) half-life (t(1/2)) of 30 (3 to 67) min. ARTS was hydrolyzed rapidly and completely to the biologically active metabolite dihydroartemisinin (DHA). Peak DHA concentrations in plasma ranged between 1,718 and 7,080 nmol/liter (median, 3,060 nmol/liter) and declined with a t(1/2) of 52 (26 to 69) min. In contrast, ARM was slowly and erratically absorbed. The absorption profile appeared biphasic. Maximum ARM concentrations in plasma ranged between 67 nmol/liter (a value close to the 50% inhibitory concentration for some Plasmodium falciparum isolates) and 1,631 nmol/liter (median, 574 nmol/liter) and occurred at a median (range) of 10 (1.5 to 24) h. There was relatively little conversion to DHA. After i.m. injection in cases of severe malaria, absorption of the water-soluble ARTS is rapid and extensive, whereas the oil-based ARM is slowly and erratically absorbed, with relatively little conversion to the more active DHA. On the basis of this pharmacological study, parenteral ARTS is preferable to ARM as an initial antimalarial therapy, particularly in the most seriously ill patients. These findings should be formally assessed by a randomized clinical trial.

The role of the polymerase chain reaction in the diagnosis of bacterial meningitis in Vietnam

Bacterial meningitis remains an important cause of morbidity and mortality in Vietnam. Diagnosis is hampered by the ready availability of antibiotics in the community, leading to late presentation, masked clinical signs, and poor organism detection during the microscopical examination and culture of cerebrospinal fluid (CSF). In order to improve organism detection at the Hospital for Tropical Diseases in Ho Chi Minh City, a diagnostic PCR-based protocol was developed. This protocol was followed in the investigation of CSF samples from 36 patients with clinical signs of bacterial meningitis. Each sample was first tested in a semi-nested PCR using primers for the 16sRNA gene common to all bacteria. The products of this reaction were then amplified using a 16sru8 primer and primers specific for Neisseria meningitidis, Haemophilus influenzae or Streptococcus spp. The samples found positive for Streptococcus were further investigated in a nested PCR using primers specific for the pneumolysin gene of S. pneumoniae. The sensitivity of detection was increased from 36% with culture to 44% with PCR. Although the sample size was small, the results indicate that PCR would be a feasible and useful adjunct in the diagnosis of bacterial meningitis, particularly in areas where community antibiotic use is common.

Factors associated with carriage of penicillin-resistant Streptococcus pneumoniae among Vietnamese children: a rural-urban divide

This study examined the relationship between antimicrobial resistance in Streptococcus pneumoniae and patterns of antimicrobial usage and over-the-counter dispensing by pharmacies in urban and rural districts of Vietnam. The antimicrobial susceptibility of S. pneumoniae carried by healthy urban and rural school children was determined. Questionnaires were distributed to parents to describe their healthcare-seeking behaviour. Mock parents presented standardized cases of mild respiratory infection and acute watery diarrhoea to pharmacies in the district surrounding each school. Penicillin resistance was significantly more common in S. pneumoniae carried by urban children compared to rural children as was recent antibiotic usage. Both urban and rural pharmacies showed high rates of dispensing inadequate antimicrobial regimens. The high level of antimicrobial resistance in S. pneumoniae may be related to greater antimicrobial usage. This may result from the much easier access to healthcare providers in urban areas and may suggest that relying solely on education without limiting access to outlets may have only limited impact. The results suggest a greater understanding of the subtleties of healthcare-seeking behaviour, and access to healthcare is needed to help refine and guide rationale suggestions to reduce the continued spread of drug resistance.

Neuropathological assessment of artemether-treated severe malaria

In animals, high doses of intramuscular artemether and artemotil have been shown to cause an unusual pattern of selective damage to certain brainstem nuclei, especially those implicated in hearing and balance. We aimed to investigate whether a similar pattern arises in human adults. We examined the brainstems of adults who died after treatment with high dose artemether or quinine for severe falciparum malaria for evidence of a pattern of selective neuronal damage. Neuropathological findings were similar in recipients of quinine (n=15) and artemether (n=6; total artemether doses received 4-44 mg/kg). No evidence was recorded for artemether-induced neurotoxic effects.

Hemochromatosis gene (HFE) mutations in South East Asia: a potential for iron overload

Hereditary hemochromatosis (HH) is an autosomal recessive disease caused by mutations in the HFE gene that mainly affects populations of European descent. Recently a novel mutation (IVS5+1 G-->A) has been described in a Vietnamese patient with HH that was not detected in a European control population. We have developed a novel method to screen for this mutation based on restriction enzyme digestion of a PCR product using a modified forward primer. We have screened 314 Vietnamese people from several ethnic groups and 154 people from Thailand for this mutation and have detected two heterozygotes in the Vietnamese subjects (allele frequency 0.003). Analysis of these heterozygotes indicates that the mutation is on the same haplotype as that found in the original proband. Screening for the widely distributed HFE mutation, H63D, gave an allele frequency of 0.049 in the Vietnamese subjects and 0.032 in the subjects from Thailand. This is the first report of H63D allele frequencies in these populations. We suggest that the presence of the IVS5+1 G-->A and H63D mutations should be considered when investigating iron overload in Vietnamese patients and those of mixed origin as co-inheritance of both mutations is likely to be a risk factor for iron overload.

Cytokine release by lipopolysaccharide-stimulated whole blood from patients with typhoid fever

The ex vivo cytokine response to lipopolysaccharide (LPS) of whole blood from patients with typhoid fever was investigated. Tumor necrosis factor (TNF)-alpha release by LPS-stimulated blood was found to be lower during acute typhoid fever than after a course of antimicrobial therapy (P<or=.001). Ex vivo interleukin (IL)-1beta, but not IL-1 receptor antagonist, release was also depressed during the acute stage of typhoid fever. Low ex vivo production of TNF-alpha was associated with delayed recovery. No association was found between the TNFA-308 promoter polymorphism and LPS-induced TNF-alpha release, either during an active infection or after treatment. In acute typhoid fever, the ability of peripheral blood leukocytes to release proinflammatory cytokines in response to an inflammatory stimulus is depressed, and this may contribute to delayed recovery following antibiotic treatment.

Malaria in injection drug abusers in Vietnam

A prospective case-control study was conducted in a referral hospital in Ho Chi Minh City, Vietnam, to compare the clinical and laboratory features and outcome of severe falciparum malaria in injection drug abusers (IDAs) with those of patients who had acquired malaria by mosquito bite. From 1991 to 1996, 70 IDAs were admitted to the hospital, of whom at least 32 had acquired malaria by needle sharing. Although IDAs were more likely than control patients with severe malaria to be malnourished and to have coincident hepatitis B, hepatitis C, and human immunodeficiency virus infections, the overall rates of mortality, complications, and recovery were similar in the 2 groups. The route of malaria acquisition did not affect the outcome of severe malaria. The management of severe malaria in IDAs is similar to that for other patients.

Assessment of the factors associated with flavivirus seroprevalence in a population in Southern Vietnam

Dengue and Japanese encephalitis flaviviruses cause severe disease and are hyperendemic in southern Vietnam. This study assesses associations between sociodemographic factors and flavivirus seroprevalence in this region. Sera were collected from 308 community and hospital-based subjects between April 1996 and August 1997 and tested with an indirect ELISA. The factors associated with seroprevalence were assessed using multivariate logistic regression. In this first report of adjusted prevalence odds ratios (POR) for flavivirus infection in Vietnam, seropositivity was associated with increasing age in children (multiple regression coefficients for a child compared to an adult = -4.975 and for age in children = 0.354) and residence in the city compared to surrounding rural districts. The association with age indicates that subjects were most likely to have acquired infection in early childhood. This is key to the design of Vietnamese health education and immunization programmes.

Short report: hepatitis b infection and severe Plasmodium falciparum malaria in Vietnamese adults

We investigated the prevalence of infection with hepatitis B virus among adult Vietnamese patients hospitalized for severe Plasmodiumfalciparum malaria. Sera from patients admitted with severe malaria in Ho Chi Minh City, Vietnam, between May 1991 and January 1996 were assayed for hepatitis B surface antigen (HB(s)Ag) by a commercial enzyme-linked immunosorbent assay kit. The overall prevalence of HB(s)Ag was 23.77% (77 of 324). This was higher than reported estimates of prevalence in the general catchment population for the study hospital (mean, 9.8%; range, 9-16%). No association was found between risk of death caused by severe malaria and HB(s)Ag. Patients admitted with cerebral malaria had a slightly greater risk of registering positive for HB(s)Ag (relative risk, 1.28; 95% confidence interval, 1.04-1.58) relative to other manifestations of severe malaria. Chronic infection with hepatitis B virus may be a risk factor for severe malaria.

Cellular stress and injury responses in the brains of adult Vietnamese patients with fatal Plasmodium falciparum malaria

Immunohistochemical techniques have been used to investigate specific patterns of potentially reversible cellular injury, DNA damage, and apoptosis in the brainstems of Vietnamese patients who died of severe Plasmodium falciparum malaria. The degree and pattern of neuronal and glial stress responses were compared between patients with cerebral and non-cerebral malaria (CM), and appropriate non-malaria infected controls. The following markers were examined: (i) heat shock protein 70 (HSP70), for reversible injury; (ii) heme oxygenase-1, for oxidative stress; (iii & iv) two DNA-repair proteins, poly(ADP) ribose polymerase (PARP) and DNA-dependent protein kinase catalytic subunit; (v) poly(ADP) ribose, an end-product of PARP activity; and (vi) caspase-3-active, for apoptosis. Stress responses were found in a range of cell types as reflected by the widespread expression of HSP70. Oxidative stress predominated in the vicinity of vessels and haemorrhages. Some degree of DNA damage was found in the majority of malaria patients, but the distribution and frequency of the damage was much less than that observed in controls with irreversible neuronal injury. Similarly, caspase-3-active expression, as a measure of apoptosis, was no higher in the majority of malaria patients than the negative control cases, although 40% of CM cases expressed caspase-3-active in a small number of neurones of the pontine nuclei or within swollen axons of the pontocerebellar and corticospinal tracts. In conclusion, cells within the brainstem of all patients who died from severe malaria showed staining patterns indicative of considerable stress response and reversible neuronal injury. There was no evidence for a specific pattern of widespread irreversible cell damage in those patients with cerebral malaria.