Publications

Significance Slow-clearing artemisinin-resistant malaria parasites are now well established in the Greater Mekong Subregion. This large multinational therapy efficacy study incorporating clinical data, molecular drug-resistance markers, and immune profiling aimed to understand how variations in population levels of naturally acquired malarial immunity affect the slow-clearing phenotype, emergence of artemisinin resistance-associated mutations, and assessment of the geographical spread of artemisinin resistance. We found that slow-clearing mutant parasites occur at higher frequencies in areas where immunity is lowest, patients with higher immunity have faster clearance times, and immunity has the greatest effect on clearance in patients with slow-clearing mutant parasites. Immunity plays an important role in the emergence of resistant parasites and can confound the World Health Organization’s phenotype and genotype definitions of artemisinin resistance.

No abstract is provided for this article.

Capillary permeability was investigated in 32 Thai patients aged 14–49 years who had acute falciparum malaria with use of three distinct techniques: quantitation of the urinary albumin/creatinine ratio (ACR), estimation of the transcapillary escape rate of radiolabeled albumin (TER), and retinal photography/fluorescein angiography. Fourteen patients had uncomplicated infections and 18 were severe cases. The severely ill patients had significantly higher ACRs (median, 4.8 mg/mmol; 95% confidence limits, 2.4–19.9 mg/mmol) and TERs (median, 8.3%/h; 95% confidence limits, 6.2–13.2%/h) than the uncomplicated cases (ACR: median, 2.1 mg/mmol; 95% confidence limits, 1.0–8.8 mg/mmol; TER: median, 5.90/0/h; 95% confidence limits, 3.8–10.6%/h; P = .014 and .042). Both variables were significantly associated with biochemical indices of disease severity including total serum bilirubin levels (rs ⩾ 0.398, P < .025 in each case), but there were no significant differences between ACRs and TERs among comatose and noncomatose patients with severe infections (P ⩾ .08). Retinopathy (hemorrhages, cotton-wool spots, capillary nonperfusion, and/or extravasation of fluorescein) was found in eight severely ill patients and in two uncomplicated cases. Fluorescein leakage was evident in six patients. Although fluorescein leakage had the strongest parametric correlation with the presence of coma relative to both ACR and TER in the full patient series (r = 0.58, P < .01), multiple linear regression analysis indicated that concentrations of plasma lactate (t = 2.998, P = .006) and serum creatinine (t = 2.200, P = .036) were the factors responsible for this association. These data do not support a role for tissue edema in the pathogenesis of cerebral malaria but reveal an association between markers of disease severity and a generalized increase in systemic capillary permeability.

Background Artemisinin-resistant falciparum malaria has arisen in western Cambodia. A concerted international effort is underway to contain artemisinin-resistant Plasmodium falciparum, but containment strategies are dependent on whether resistance has emerged elsewhere. We aimed to establish whether artemisinin resistance has spread or emerged on the Thailand–Myanmar (Burma) border. Methods In malaria clinics located along the northwestern border of Thailand, we measured six hourly parasite counts in patients with uncomplicated hyperparasitaemic falciparum malaria (≥4% infected red blood cells) who had been given various oral artesunate-containing regimens since 2001. Parasite clearance half-lives were estimated and parasites were genotyped for 93 single nucleotide polymorphisms. Findings 3202 patients were studied between 2001 and 2010. Parasite clearance half-lives lengthened from a geometric mean of 2·6 h (95% CI 2·5–2·7) in 2001, to 3·7 h (3·6–3·8) in 2010, compared with a mean of 5·5 h (5·2–5·9) in 119 patients in western Cambodia measured between 2007 and 2010. The proportion of slow-clearing infections (half-life ≥6·2 h) increased from 0·6% in 2001, to 20% in 2010, compared with 42% in western Cambodia between 2007 and 2010. Of 1583 infections genotyped, 148 multilocus parasite genotypes were identified, each of which infected between two and 13 patients. The proportion of variation in parasite clearance attributable to parasite genetics increased from 30% between 2001 and 2004, to 66% between 2007 and 2010. Interpretation Genetically determined artemisinin resistance in P falciparum emerged along the Thailand–Myanmar border at least 8 years ago and has since increased substantially. At this rate of increase, resistance will reach rates reported in western Cambodia in 2–6 years. Funding The Wellcome Trust and National Institutes of Health.

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.

Background Japanese encephalitis virus (JEV), although confined to Asia, causes about 35 000–50 000 cases and 10 000 deaths every year, and is the most important cause of encephalitis worldwide. There is no known antiviral treatment for any flavivirus. Results from in-vitro studies and work in animals have shown inteferon alfa has antiviral activity on Japanese encephalitis and other flaviviruses; therefore, we aimed to assess the efficacy of inteferon alfa-2a in Japanese encephalitis. Methods We did a randomised double-blind placebo-controlled trial of interferon alfa-2a (10 million units/m 2 , daily for 7 days) in 112 Vietnamese children with suspected Japanese encephalitis, 87 of whom had serologically confirmed infections. Our primary endpoints were hospital death or severe sequelae at discharge. Analysis was by intention to treat. Findings Overall, 21 children (19%) died, and 17 (15%) had severe sequelae. Outcome at discharge and 3 months did not differ between the two treatment groups; 20 children in the interferon group had a poor outcome (death or severe sequelae), compared with 18 in the placebo group (p=0·85, difference 0·1%, 95% CI −17·5 to 17·6%), there were no long-term side effects of interferon. Interpretation The doses of interferon alfa-2a given in this regimen did not improve the outcome of patients with Japanese encephalitis. Published online February 11,2003 http://image.thelancet.com/extras/02art9329web.pdf

No abstract is provided for this article.

The plasma concentrations of quinine and its main metabolite, 3-hydroxyquinine (3OHQn), were measured in 5 adult Thai patients with severe Plasmodium falciparum malaria and acute renal failure. Two patients required peritoneal dialysis but all survived. During acute renal failure plasma concentrations of 3OHQn rose to reach up to 45% of the levels of the parent compound. The estimated median (range) quinine clearance was 0·83 mL/kg/min (0·58-1·16), and 3OHQn clearance/fraction of quinine converted was 3·40 mL/kg/min (2·58-4.47). The estimated 3OHQn terminal elimination half-life was 21 h (16·5–32·5). These data suggest that 3OHQn contributes about 12% of the antimalarial activity of the parent compound in patients with falciparum malaria and acute renal failure. It is also likely that 3OHQn contributes to adverse effects, although this metabolite is not quantitated routinely by current highperformance liquid chromatography quinine assays.

A randomised trial was conducted in adults and children (> 1 year old) with acute falciparum malaria in Western Myanmar to compare the operational effectiveness of 4 different artesunate-mefloquine combinations. All regimens were well tolerated. During 42 days follow-up polymerase chain reaction genotyping-confirmed recrudescence occurred in 11 of 187 (5.9%) patients who received observed single low-dose mefloquine (15 mg/kg) and artesunate (4 mg/kg), 7 of 192 (3.6%) patients following observed single high-dose mefloquine (25 mg/kg) and artesunate (4 mg/kg), 7 of 180 (3.9%) patients following observed artesunate 4 mg/kg on day 0 plus self-administered mefloquine 15 mg/kg on day 1 and 10 mg/kg on day 2 with artesunate 4 mg/kg/day on day 1 and 2, and none of 177 patients who received this 3 d regimen under direct observation (P = 0.01). Compared with 3 d treatment regimens, single dose treatments were followed by significantly more P vivax infections during the 42 d follow-up (P = 0.009). Post treatment anaemia (haemoglobin < 10 g/dL) was reduced by the 3 d regimens. Gametocyte appearance was low with all 4 regimens. Single dose observed mefloquine-artesunate regimens were very effective, but the 3 d artesunate-mefloquine regimen is the best treatment for acute falciparum malaria in Western Myanmar. Active measures to ensure absorption and improve adherence will be necessary to realise this advantage operationally.

Tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, and IL-6 are implicated in the pathogenesis of severe Plasmodium falciparum malaria. In this study, the effect of IL-10 on their production by peripheral blood mononuclear cells (PBMC) from acutely infected patients was examined. Exogenous IL-10 inhibited malarial antigen-induced cytokine production by reducing mRNA accumulation. Maximal inhibition occurred when IL-10 was added in the first 2 h of stimulation. Conversely, the addition of anti-IL-10 markedly enhanced TNF-alpha, IL-1beta, and IL-6 production. The effect was significantly greater on PBMC from patients with uncomplicated infection than PBMC from patients with severe disease. Kinetics studies showed that TNF-alpha, IL-6, and IL-1beta were produced within 2-4 h of stimulation, while IL-10 was first detectable after 8 h. These findings suggest that IL-10 counter-regulates the proinflammatory response to P. falciparum. Severe falciparum malaria may be associated with an inadequate negative feedback response by IL-10.