Search tips
Search criteria

Results 1-25 (60)

Clipboard (0)

Select a Filter Below

Year of Publication
more »
1.  Leptospira Species in Floodwater during the 2011 Floods in the Bangkok Metropolitan Region, Thailand 
Floodwater samples (N = 110) collected during the 2011 Bangkok floods were tested for Leptospira using culture and polymerase chain reaction (PCR); 65 samples were PCR-positive for putatively non-pathogenic Leptospira species, 1 sample contained a putatively pathogenic Leptospira, and 6 samples contained Leptospira clustering phylogenetically with the intermediate group. The low prevalence of pathogenic and intermediate Leptospira in floodwater was consistent with the low number of human leptospirosis cases reported to the Bureau of Epidemiology in Thailand. This study provides baseline information on environmental Leptospira in Bangkok together with a set of laboratory tests that could be readily deployed in the event of future flooding.
PMCID: PMC3795115  PMID: 24002484
2.  Gametocyte Dynamics and the Role of Drugs in Reducing the Transmission Potential of Plasmodium vivax 
The Journal of Infectious Diseases  2013;208(5):801-812.
Background. Designing interventions that will reduce transmission of vivax malaria requires knowledge of Plasmodium vivax gametocyte dynamics.
Methods. We analyzed data from a randomized controlled trial in northwestern Thailand and 2 trials in Papua, Indonesia, to identify and compare risk factors for vivax gametocytemia at enrollment and following treatment.
Results. A total of 492 patients with P. vivax infections from Thailand and 476 patients (162 with concurrent falciparum parasitemia) from Indonesia were evaluable. Also, 84.3% (415/492) and 66.6% (209/314) of patients with monoinfection were gametocytemic at enrollment, respectively. The ratio of gametocytemia to asexual parasitemia did not differ between acute and recurrent infections (P = .48 in Thailand, P = .08 in Indonesia). High asexual parasitemia was associated with an increased risk of gametocytemia during follow-up in both locations. In Thailand, the cumulative incidence of gametocytemia between day 7 and day 42 following dihydroartemisinin + piperaquine (DHA + PIP) was 6.92% vs 29.1% following chloroquine (P < .001). In Indonesia, the incidence of gametocytemia was 33.6% following artesunate + amodiaquine (AS + AQ), 7.42% following artemether + lumefantrine, and 6.80% following DHA + PIP (P < .001 for DHA + PIP vs AS + AQ).
Conclusions. P. vivax gametocyte carriage mirrors asexual-stage infection. Prevention of relapses, particularly in those with high asexual parasitemia, is likely the most important strategy for interrupting P. vivax transmission.
PMCID: PMC3733516  PMID: 23766527
Plasmodium vivax; gametocytes; antimalarial drugs; epidemiology; transmission
3.  Malaria in the Post-Partum Period; a Prospective Cohort Study 
PLoS ONE  2013;8(3):e57890.
Several studies have shown a prolonged or increased susceptibility to malaria in the post-partum period. A matched cohort study was conducted to evaluate prospectively the susceptibility to malaria of post-partum women in an area where P.falciparum and P.vivax are prevalent.
In an area of low seasonal malaria transmission on the Thai-Myanmar border pregnant women attending antenatal clinics were matched to a non-pregnant, non-post-partum control and followed up prospectively until 12 weeks after delivery.
Post-partum women (n = 744) experienced significantly less P.falciparum episodes than controls (hazard ratio (HR) 0.39 (95%CI 0.21–0.72) p = 0.003) but significantly more P.vivax (HR 1.34 (1.05–1.72) p = 0.018). The reduced risk of falciparum malaria was accounted for by reduced exposure, whereas a history of P.vivax infection during pregnancy was a strong risk factor for P.vivax in post-partum women (HR 13.98 (9.13–21.41), p<0.001). After controlling for effect modification by history of P.vivax, post-partum women were not more susceptible to P.vivax than controls (HR: 0.33 (0.21–0.51), p<0.001). Genotyping of pre-and post-partum infections (n⊕ = ⊕10) showed that each post-partum P.falciparum was a newly acquired infection.
In this area of low seasonal malaria transmission post-partum women were less likely to develop falciparum malaria but more likely to develop vivax malaria than controls. This was explained by reduced risk of exposure and increased risk of relapse, respectively. There was no evidence for altered susceptibility to malaria in the post-partum period. The treatment of vivax malaria during and immediately after pregnancy needs to be improved.
PMCID: PMC3596341  PMID: 23516418
4.  Malaria Burden and Artemisinin Resistance in the Mobile and Migrant Population on the Thai–Myanmar Border, 1999–2011: An Observational Study 
PLoS Medicine  2013;10(3):e1001398.
Francois Nosten and colleagues evaluate malaria prevalence and incidence in the mobile population on the Myanmar side of the border with Thailand between 1999 and 2011, and also assess resistance to artemisinin.
The Shoklo Malaria Research Unit has been working on the Thai–Myanmar border for 25 y providing early diagnosis and treatment (EDT) of malaria. Transmission of Plasmodium falciparum has declined, but resistance to artesunate has emerged. We expanded malaria activities through EDT and evaluated the impact over a 12-y period.
Methods and Findings
Between 1 October 1999 and 30 September 2011, the Shoklo Malaria Research Unit increased the number of cross-border (Myanmar side) health facilities from two to 11 and recorded the number of malaria consultations. Changes in malaria incidence were estimated from a cohort of pregnant women, and prevalence from cross-sectional surveys. In vivo and in vitro antimalarial drug efficacy were monitored. Over this period, the number of malaria cases detected increased initially, but then declined rapidly. In children under 5 y, the percentage of consultations due to malaria declined from 78% (95% CI 76–80) (1,048/1,344 consultations) to 7% (95% CI 6.2–7.1) (767/11,542 consultations), p<0.001. The ratio of P. falciparum/P. vivax declined from 1.4 (95% CI 1.3–1.4) to 0.7 (95% CI 0.7–0.8). The case fatality rate was low (39/75,126; 0.05% [95% CI 0.04–0.07]). The incidence of malaria declined from 1.1 to 0.1 episodes per pregnant women-year. The cumulative proportion of P. falciparum decreased significantly from 24.3% (95% CI 21.0–28.0) (143/588 pregnant women) to 3.4% (95% CI 2.8–4.3) (76/2,207 pregnant women), p<0.001. The in vivo efficacy of mefloquine-artesunate declined steadily, with a sharp drop in 2011 (day-42 PCR-adjusted cure rate 42% [95% CI 20–62]). The proportion of patients still slide positive for malaria at day 3 rose from 0% in 2000 to reach 28% (95% CI 13–45) (8/29 patients) in 2011.
Despite the emergence of resistance to artesunate in P. falciparum, the strategy of EDT with artemisinin-based combination treatments has been associated with a reduction in malaria in the migrant population living on the Thai–Myanmar border. Although limited by its observational nature, this study provides useful data on malaria burden in a strategically crucial geographical area. Alternative fixed combination treatments are needed urgently to replace the failing first-line regimen of mefloquine and artesunate.
Please see later in the article for the Editors' Summary
Editors' Summary
According to latest figures, the World Health Organization estimates that there are over 200 million cases of malaria each year, with over three-quarters of a million deaths. Several Plasmodium parasites cause malaria (the most serious being Plasmodium falciparum) and are transmitted to people through the bites of infected night-flying mosquitoes. Malaria transmission can be prevented by using insecticides to control the mosquitoes and by sleeping under insecticide-treated bed nets. However, in Southeast Asia the effectiveness of these measures is limited. Treating infected people with antimalarial drugs, particularly with artemisinin-based combination treatments (ACTs), is a key strategy in reducing the deaths and disability caused by malaria. However, progress is now threatened by the emergence in Southeast Asia of P. falciparum isolates that are resistant to artesunate (a common component of ACT). This development is concerning, as resistance to the artemisinin family of drugs, of which artesunate is a member, could trigger a resurgence in malaria in many parts of the world and compromise the progress made in the treatment of severe malaria.
Why Was This Study Done?
P. falciparum resistance to artemisinin has been confirmed in the area around the border between Thailand and Myanmar. Malaria control in this border area is particularly challenging, as there is a reservoir of malaria in Myanmar (where the disease burden is higher than in Thailand), frequent population movement, and differences in adequate control measures on the two sides of the border. In this study the authors evaluated malaria prevalence and incidence in the mobile population on the Myanmar side of the border between 1 October 1999 and 30 September 2011 to assess whether increasing access to early diagnosis and treatment with ACT was associated with a decline in the malaria burden.
What Did the Researchers Do and Find?
The Shoklo Malaria Research Unit (SMRU) has been working on the Thai–Myanmar border for 25 years providing early diagnosis and treatment of malaria and has extended its services from two to 11 health care facilities (health posts) on the Myanmar side of the border over the past few years. In order to evaluate any changes in the malaria burden since the expansion of services, the researchers recorded the number of consultations in all SMRU clinics and health posts with confirmed malaria diagnosis and tracked changes in the prevalence of malaria in the population on the Myanmar side of the border (via cross-sectional surveys in villages). The researchers also assessed the incidence of malaria in a cohort of pregnant women living on both sides of the border and monitored antimalarial drug efficacy over this time period.
The researchers found that although the mobile population on the Thai side of the border remained constant, the population in villages covered by the clinics and health posts in the border area increased four-fold. Over the time period, the researchers found that the number of confirmed malaria cases (P. falciparum) increased initially, rising from just over 5,000 in 2000 to a peak of 13,764 in 2006, and then declined to just over 3,500 in 2011. A striking finding was the predominance of infections in young adult males (50,316/90,321; 55.7%). Encouragingly, the percentage of consultations due to malaria in children under five years fell from 78% to 7%, and the incidence of malaria declined from 1.1 to 0.1 episodes per pregnant woman-year. In addition, the proportion of patients admitted to hospital with severe disease was stable, and the number of deaths from malaria remained extremely low, with an overall case fatality rate of 0.05%. The researchers also found that the ratio of P. falciparum to P. vivax infections declined from 1.4 to 0.7, and the prevalence of P. falciparum decreased from 24.3% to 3.4%. However, worryingly, in the small number of patients undertaking drug efficacy tests, the drug efficacy of artesunate declined steadily, with the proportion of patients still infected with malaria at day 3 of treatment increasing from 0% in 2000 to 28% in 2011.
What Do These Findings Mean?
These findings indicate that despite the emergence of resistance to artesunate in P. falciparum, and the decline in the efficacy of ACT, the strategy of early diagnosis and treatment with ACTs has been associated with a reduction in malaria in the population living on the Thai–Myanmar border. Furthermore, these findings suggest that an aggressive strategy based on early detection and treatment of cases, combined with vector control and information, could be the way forward to eliminate malaria. Although there were only a small number of patients involved in drug efficacy tests in 2011, this study shows that alternative fixed combination treatments are needed urgently to replace the failing first-line regimen of mefloquine and artesunate.
Additional Information
Please access these websites via the online version of this summary at
More information about the Shoklo Malaria Research Unit is available
The World Health Organization website has more information about antimalarial drug efficacy and drug resistance
The Bill & Melinda Gates Foundation website tells the malaria resistance story
PMCID: PMC3589269  PMID: 23472056
5.  Artesunate/dihydroartemisinin pharmacokinetics in acute falciparum malaria in pregnancy: absorption, bioavailability, disposition and disease effects 
To determine if reported lower plasma concentrations of artemisinin derivatives for malaria in pregnancy result from reduced oral bioavailability, expanded volume of distribution or increased clearance.
In a sequentially assigned crossover treatment study, pregnant women with uncomplicated falciparum malaria received i.v. artesunate (i.v. ARS) (4 mg kg−1) on the first day and oral ARS (4 mg kg−1) on the second, or, oral on the first and i.v. on the second, in both groups followed by oral ARS (4 mg kg−1 day−1) for 5 days. Plasma concentrations of ARS and dihyroartemisinin (DHA) were measured by liquid chromatography-mass-spectrometry on days 0, 1, 2 and 6. Controls were the same women restudied when healthy (3 months post partum).
I.v. ARS administration resulted in similar ARS and DHA pharmacokinetics in pregnant women with malaria (n = 20) and in controls (n = 14). Oral administration resulted in higher total drug exposure in pregnancy [AUC (95% CI) in (ng ml−1 h)/(mg kg−1)] of 55.1 (30.1, 100.0) vs. 26.5 (12.2, 54.3) for ARS, P = 0.002 and 673 (386, 1130) vs. 523 (351, 724) for DHA, P = 0.007. The corresponding median absolute oral bioavailability (F%) was 21.7 (12.6, 75.1) vs. 9.9 (6.0, 36.81) for ARS (P = 0.046) and 77.0 (42.2, 129) vs. 72.7 (42.0, 87.7) for DHA, P = 0.033. Total DHA exposure was lower at day 6 in pregnant women with malaria (P < 0.001) compared with day 0 or 1, but not in the controls (P = 0.084).
This study demonstrates the effects of malaria on oral ARS drug disposition are greater than those of pregnancy. This probably results from a disease related reduction in first pass metabolism. The data are reassuring regarding current dosing recommendations.
PMCID: PMC3370352  PMID: 21950338
artesunate; dihyroartemisinin; malaria; pharmacokinetics; post partum; pregnancy
6.  An analysis of health system resources in relation to pandemic response capacity in the Greater Mekong Subregion 
There is increasing perception that countries cannot work in isolation to militate against the threat of pandemic influenza. In the Greater Mekong Subregion (GMS) of Asia, high socio-economic diversity and fertile conditions for the emergence and spread of infectious diseases underscore the importance of transnational cooperation. Investigation of healthcare resource distribution and inequalities can help determine the need for, and inform decisions regarding, resource sharing and mobilisation.
We collected data on healthcare resources deemed important for responding to pandemic influenza through surveys of hospitals and district health offices across four countries of the GMS (Cambodia, Lao PDR, Thailand, Vietnam). Focusing on four key resource types (oseltamivir, hospital beds, ventilators, and health workers), we mapped and analysed resource distributions at province level to identify relative shortages, mismatches, and clustering of resources. We analysed inequalities in resource distribution using the Gini coefficient and Theil index.
Three quarters of the Cambodian population and two thirds of the Laotian population live in relatively underserved provinces (those with resource densities in the lowest quintile across the region) in relation to health workers, ventilators, and hospital beds. More than a quarter of the Thai population is relatively underserved for health workers and oseltamivir. Approximately one fifth of the Vietnamese population is underserved for beds and ventilators. All Cambodian provinces are underserved for at least one resource. In Lao PDR, 11 percent of the population is underserved by all four resource items. Of the four resources, ventilators and oseltamivir were most unequally distributed. Cambodia generally showed higher levels of inequalities in resource distribution compared to other countries. Decomposition of the Theil index suggests that inequalities result principally from differences within, rather than between, countries.
There is considerable heterogeneity in healthcare resource distribution within and across countries of the GMS. Most inequalities result from within countries. Given the inequalities, mismatches, and clustering of resources observed here, resource sharing and mobilization in a pandemic scenario could be crucial for more effective and equitable use of the resources that are available in the GMS.
PMCID: PMC3556110  PMID: 23241450
Health system; Pandemic influenza; Health equity; Resource mapping; Resource allocation; Antivirals; Southeast Asia
7.  Artemisinin Resistance in Plasmodium falciparum Malaria 
The New England journal of medicine  2009;361(5):455-467.
Artemisinin-based combination therapies are the recommended first-line treatments of falciparum malaria in all countries with endemic disease. There are recent concerns that the efficacy of such therapies has declined on the Thai–Cambodian border, historically a site of emerging antimalarial-drug resistance.
In two open-label, randomized trials, we compared the efficacies of two treatments for uncomplicated falciparum malaria in Pailin, western Cambodia, and Wang Pha, northwestern Thailand: oral artesunate given at a dose of 2 mg per kilogram of body weight per day, for 7 days, and artesunate given at a dose of 4 mg per kilogram per day, for 3 days, followed by mefloquine at two doses totaling 25 mg per kilogram. We assessed in vitro and in vivo Plasmodium falciparum susceptibility, artesunate pharmacokinetics, and molecular markers of resistance.
We studied 40 patients in each of the two locations. The overall median parasite clearance times were 84 hours (interquartile range, 60 to 96) in Pailin and 48 hours (interquartile range, 36 to 66) in Wang Pha (P<0.001). Recrudescence confirmed by means of polymerase-chain-reaction assay occurred in 6 of 20 patients (30%) receiving artesunate monotherapy and 1 of 20 (5%) receiving artesunate–mefloquine therapy in Pailin, as compared with 2 of 20 (10%) and 1 of 20 (5%), respectively, in Wang Pha (P = 0.31). These markedly different parasitologic responses were not explained by differences in age, artesunate or dihydroartemisinin pharmacokinetics, results of isotopic in vitro sensitivity tests, or putative molecular correlates of P. falciparum drug resistance (mutations or amplifications of the gene encoding a multidrug resistance protein [PfMDR1] or mutations in the gene encoding sarco–endoplasmic reticulum calcium ATPase6 [PfSERCA]). Adverse events were mild and did not differ significantly between the two treatment groups.
P. falciparum has reduced in vivo susceptibility to artesunate in western Cambodia as compared with northwestern Thailand. Resistance is characterized by slow parasite clearance in vivo without corresponding reductions on conventional in vitro susceptibility testing. Containment measures are urgently needed. ( number, NCT00493363, and Current Controlled Trials number, ISRCTN64835265.)
PMCID: PMC3495232  PMID: 19641202
8.  Population Pharmacokinetic and Pharmacodynamic Modeling of Amodiaquine and Desethylamodiaquine in Women with Plasmodium vivax Malaria during and after Pregnancy 
Antimicrobial Agents and Chemotherapy  2012;56(11):5764-5773.
Amodiaquine is effective for the treatment of Plasmodium vivax malaria, but there is little information on the pharmacokinetic and pharmacodynamic properties of amodiaquine in pregnant women with malaria. This study evaluated the population pharmacokinetic and pharmacodynamic properties of amodiaquine and its biologically active metabolite, desethylamodiaquine, in pregnant women with P. vivax infection and again after delivery. Twenty-seven pregnant women infected with P. vivax malaria on the Thai-Myanmar border were treated with amodiaquine monotherapy (10 mg/kg/day) once daily for 3 days. Nineteen women, with and without P. vivax infections, returned to receive the same amodiaquine dose postpartum. Nonlinear mixed-effects modeling was used to evaluate the population pharmacokinetic and pharmacodynamic properties of amodiaquine and desethylamodiaquine. Amodiaquine plasma concentrations were described accurately by lagged first-order absorption with a two-compartment disposition model followed by a three-compartment disposition of desethylamodiaquine under the assumption of complete in vivo conversion. Body weight was implemented as an allometric function on all clearance and volume parameters. Amodiaquine clearance decreased linearly with age, and absorption lag time was reduced in pregnant patients. Recurrent malaria infections in pregnant women were modeled with a time-to-event model consisting of a constant-hazard function with an inhibitory effect of desethylamodiaquine. Amodiaquine treatment reduced the risk of recurrent infections from 22.2% to 7.4% at day 35. In conclusion, pregnancy did not have a clinically relevant impact on the pharmacokinetic properties of amodiaquine or desethylamodiaquine. No dose adjustments are required in pregnancy.
PMCID: PMC3486620  PMID: 22926572
9.  Artemisinin resistance containment project in Thailand. II: responses to mefloquine-artesunate combination therapy among falciparum malaria patients in provinces bordering Cambodia 
Malaria Journal  2012;11:300.
The area along the Thai-Cambodian border is considered an epicenter of anti-malarial drug resistance. Recently, parasite resistance to artemisinin-based therapies has been reported in the area. The artemisinin resistance containment project was initiated in November 2008, with the aim to limit resistant parasites and eliminate malaria in this region. This study describes the response to artemisinin-based therapy among falciparum malaria patients in the area, using data from the malaria surveillance programmed under the containment project.
The study was conducted in seven provinces of Thailand along the Thai-Cambodian border. Data of Plasmodium falciparum-positive patients during January 2009 to December 2011 were obtained from the electronic malaria information system (eMIS) Web-based reporting system. All P. falciparum cases were followed for 42 days, as the routine case follow-up protocol. The demographic characteristics of the patients were described. Statistical analysis was performed to determine the cure rate of the current standard anti-malarial drug regimen--mefloquine-artesunate combination therapy (MAS). The proportion of patients who remained parasite-positive at each follow-up day was calculated. In addition, factors related to the delayed parasite clearance on day-3 post-treatment, were explored.
A total of 1,709 P. falciparum-positive cases were reported during the study period. Almost 70% of falciparum cases received MAS therapy (n = 1,174). The majority of cases were males, aged between 31 and 50 years. The overall MAS cure rate was >90% over the three-year period. Almost all patients were able to clear the parasite within 7 to 14 days post-treatment. Approximately 14% of patients undergoing MAS remained parasite-positive on day-3. Delayed parasite clearance was not significantly associated with patient gender, age, or citizenship. However, delayed parasite clearance varied across the study area.
Anti-malarial drug-resistant parasites should be closely monitored in the area along the Thai-Cambodian border. Although the MAS cure rate in this study area was above 90%, an increasing trend of treatment failure has been reported in neighboring parts. Effective malaria surveillance is an important component to monitor drug-resistance in the malaria containment project.
PMCID: PMC3445821  PMID: 22929621
Malaria containment; Artemisinin resistance; Thai-Cambodian border; Malaria surveillance
10.  Artemisinin resistance containment project in Thailand. (I): Implementation of electronic-based malaria information system for early case detection and individual case management in provinces along the Thai-Cambodian border 
Malaria Journal  2012;11:247.
The Bureau of Vector-borne Diseases, Ministry of Public Health, Thailand, has implemented an electronic Malaria Information System (eMIS) as part of a strategy to contain artemisinin resistance. The attempt corresponds to the WHO initiative, funded by the Bill & Melinda Gates Foundation, to contain anti-malarial drug resistance in Southeast Asia. The main objective of this study was to demonstrate the eMIS’ functionality and outputs after implementation for use in the Thailand artemisinin-resistance containment project.
The eMIS had been functioning since 2009 in seven Thai-Cambodian border provinces. The eMIS has covered 61 malaria posts/clinics, 27 Vector-borne Disease Units covering 12,508 hamlets at risk of malaria infections. The eMIS was designed as an evidence-based and near real-time system to capture data for early case detection, intensive case investigation, monitoring drug compliance and on/off-site tracking of malarial patients, as well as collecting data indicating potential drug resistance among patients. Data captured by the eMIS in 2008–2011 were extracted and presented.
The core functionalities of the eMIS have been utilized by malaria staff at all levels, from local operational units to ministerial management. The eMIS case detection module suggested decreasing trends during 2009–2011; the number of malaria cases detected in the project areas over the years studied were 3818, 2695, and 2566, with sero-positive rates of 1.24, 0.98, and 1.16%, respectively. The eMIS case investigation module revealed different trends in weekly Plasmodium falciparum case numbers, when classified by responsible operational unit, local and migrant status, and case-detection type. It was shown that most Thai patients were infected within their own residential district, while migrants were infected either at their working village or from across the border. The data mapped in the system suggested that P. falciparum-infected cases and potential drug-resistant cases were scattered mostly along the border villages. The mobile technology application has detected different follow-up rates, with particularly low rates among seasonal and cross-border migrants.
The eMIS demonstrated that it could capture essential data from individual malaria cases at local operational units, while effectively being used for situation and trend analysis at upper-management levels. The system provides evidence-based information that could contribute to the control and containment of resistant parasites. Currently, the eMIS is expanding beyond the Thai-Cambodian project areas to the provinces that lie along the Thai-Myanmar border.
PMCID: PMC3464131  PMID: 22839508
Malaria containment; Electronic-based; Information system; Malaria surveillance
11.  Effect of Early Detection and Treatment on Malaria Related Maternal Mortality on the North-Western Border of Thailand 1986–2010 
PLoS ONE  2012;7(7):e40244.
Maternal mortality is high in developing countries, but there are few data in high-risk groups such as migrants and refugees in malaria-endemic areas. Trends in maternal mortality were followed over 25 years in antenatal clinics prospectively established in an area with low seasonal transmission on the north-western border of Thailand.
Methods and Findings
All medical records from women who attended the Shoklo Malaria Research Unit antenatal clinics from 12th May 1986 to 31st December 2010 were reviewed, and maternal death records were analyzed for causality. There were 71 pregnancy-related deaths recorded amongst 50,981 women who attended antenatal care at least once. Three were suicide and excluded from the analysis as incidental deaths. The estimated maternal mortality ratio (MMR) overall was 184 (95%CI 150–230) per 100,000 live births. In camps for displaced persons there has been a six-fold decline in the MMR from 499 (95%CI 200–780) in 1986–90 to 79 (40–170) in 2006–10, p<0.05. In migrants from adjacent Myanmar the decline in MMR was less significant: 588 (100–3260) to 252 (150–430) from 1996–2000 to 2006–2010. Mortality from P.falciparum malaria in pregnancy dropped sharply with the introduction of systematic screening and treatment and continued to decline with the reduction in the incidence of malaria in the communities. P.vivax was not a cause of maternal death in this population. Infection (non-puerperal sepsis and P.falciparum malaria) accounted for 39.7 (27/68) % of all deaths.
Frequent antenatal clinic screening allows early detection and treatment of falciparum malaria and substantially reduces maternal mortality from P.falciparum malaria. No significant decline has been observed in deaths from sepsis or other causes in refugee and migrant women on the Thai–Myanmar border.
PMCID: PMC3399834  PMID: 22815732
12.  The effects of serum lipids on the in vitro activity of lumefantrine and atovaquone against Plasmodium falciparum 
Malaria Journal  2012;11:177.
Lumefantrine and atovaquone are highly lipophilic anti-malarial drugs. As a consequence absorption is increased when the drugs are taken together with a fatty meal, but the free fraction of active drug decreases in the presence of triglyceride-rich plasma lipoproteins. In this study, the consequences of lipidaemia on anti-malarial drug efficacy were assessed in vitro.
Serum was obtained from non-immune volunteers under fasting conditions and after ingestion of a high fat meal and used in standard Plasmodium falciparum in-vitro susceptibility assays. Anti-malarial drugs, including lumefantrine, atovaquone and chloroquine in five-fold dilutions (range 0.05 ng/ml – 1 ug/mL) were diluted in culture medium supplemented with fasting or post-prandial 10% donor serum. The in-vitro drug susceptibility of parasite isolates was determined using the 3H-hypoxanthine uptake inhibition method and expressed as the concentration which gave 50% inhibition of hypoxanthine uptake (IC50).
Doubling plasma triglyceride concentrations (from 160 mg/dL to 320 mg/dL), resulted in an approximate doubling of the IC50 for lumefantrine (191 ng/mL to 465 ng/mL, P < 0.01) and a 20-fold increase in the IC50 for atovaquone (0.5 ng/mL to 12 ng/ml; P < 0.01). In contrast, susceptibility to the hydrophilic anti-malarial chloroquine did not change in relation to triglyceride content of the medium.
Lipidaemia reduces the anti-malarial activity of lipophilic anti-malarial drugs. This is an important confounder in laboratory in vitro testing and it could have therapeutic relevance.
PMCID: PMC3426466  PMID: 22640826
Malaria; Anti-malarial drugs; In vitro-susceptibility
13.  Emergence of artemisinin-resistant malaria on the western border of Thailand: a longitudinal study 
Lancet  2012;379(9830):1960-1966.
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.
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.
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.
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.
The Wellcome Trust and National Institutes of Health.
PMCID: PMC3525980  PMID: 22484134
14.  Randomized, Double-Blind, Placebo-Controlled Trial of Monthly versus Bimonthly Dihydroartemisinin-Piperaquine Chemoprevention in Adults at High Risk of Malaria 
Intermittent preventive treatment (IPT) is increasingly used to reduce malaria morbidity and mortality in children and pregnant women. The efficacy of IPT depends on the pharmacokinetic and pharmacodynamic properties of the antimalarial drugs used. Healthy adult male volunteers whose occupation put them at high risk of malaria on the Northwest border of Thailand were randomized to receive a 3-day-treatment dose of dihydroartemisinin-piperaquine monthly (DPm) or every 2 months (DPalt) or an identical placebo with or without fat (6.4g/dose) over a 9-month period. All volunteers were monitored weekly. One thousand adults were recruited. Dihydroartemisinin-piperaquine was well tolerated. There were 114 episodes of malaria (49 Plasmodium falciparum, 63 P. vivax, and 2 P. ovale). The protective efficacy against all malaria at 36 weeks was 98% (95% confidence interval [CI], 96% to 99%) in the DPm group and 86% (95% CI, 81% to 90%) in the DPalt group (for both, P < 0.0001 compared to the placebo group). As a result, the placebo group also had lower hematocrits during the study (P < 0.0001). Trough plasma piperaquine concentrations were the main determinant of efficacy; no malaria occurred in participants with a trough concentration above 31 ng/ml. Neither plasma piperaquine concentration nor efficacy was influenced by the coadministration of fat. DPm is safe to use and is effective in the prevention of malaria in adult males living in an area where P. vivax and multidrug-resistant P. falciparum malaria are endemic.
PMCID: PMC3294930  PMID: 22252804
15.  Pharmacokinetics of Dihydroartemisinin and Piperaquine in Pregnant and Nonpregnant Women with Uncomplicated Falciparum Malaria▿† 
Antimicrobial Agents and Chemotherapy  2011;55(12):5500-5506.
Dihydroartemisinin-piperaquine is a fixed-dose artemisinin-based combination treatment. Some antimalarials have altered pharmacokinetics in pregnancy. Pregnant women in the 2nd or 3rd trimester and matched nonpregnant women with uncomplicated falciparum malaria were treated with a total of 6.4 mg/kg of body weight dihydroartemisinin and 51.2 mg/kg piperaquine once daily for 3 days. Venous blood samples were drawn at prespecified time points over 9 weeks. Plasma dihydroartemisinin and piperaquine concentrations were analyzed by liquid chromatography-mass spectrometry. Piperaquine and dihydroartemisinin pharmacokinetics were well described. There were no significant differences in total piperaquine exposure (P = 0.80) or drug exposure during the terminal elimination phase (72 h to infinity) (P = 0.64) between the two groups. The apparent volume of distribution of piperaquine was significantly smaller (602 liters/kg versus 877 liters/kg) in pregnant women than in nonpregnant women (P = 0.0057), and the terminal elimination half-life was significantly shorter (17.8 days versus 25.6 days; P = 0.0023). Dihydroartemisinin exposure after the first dose was significantly lower (844 h × ng/ml versus 1,220 h × ng/ml, P = 0.0021) in pregnant women, but there were no significant differences in total dihydroartemisinin exposure or maximum concentrations between the two groups. There were no significant differences in any pharmacokinetic parameters between the second and third trimester. These results obtained through noncompartmental analysis suggest that in the treatment of falciparum malaria, there are no clinically important differences in the pharmacokinetics of dihydroartemisinin or piperaquine between pregnant and nonpregnant women. However, a more detailed analysis using population pharmacokinetic modeling is needed to fully investigate the differences found for some of the pharmacokinetic parameters, such as the terminal half-life.
PMCID: PMC3232755  PMID: 21947392
16.  Dihydroartemisinin-Piperaquine Versus Chloroquine in the Treatment of Plasmodium vivax Malaria in Thailand: A Randomized Controlled Trial 
The efficacy of chloroquine in the treatment of Plasmodium vivax malaria is declining on the Northwestern border of Thailand. This randomized controlled trial in 500 adults and children shows that dihydroartemisinin-piperaquine is a safe and effective alternative treatment.
Background. Chloroquine (CQ) remains the treatment of choice for Plasmodium vivax malaria. Initially confined to parts of Indonesia and Papua, resistance of P. vivax to CQ seems to be spreading, and alternative treatments are required.
Methods. We conducted a randomized controlled study to compare the efficacy and the tolerability of CQ and dihydroartemisinin-piperaquine (DP) in 500 adults and children with acute vivax malaria on the Northwestern border of Thailand.
Results. Both drugs were well tolerated. Fever and parasite clearance times were slower in the CQ than in the DP group (P < .001). By day 28, recurrent infections had emerged in 18 of 207 CQ recipients compared with 5 of 230 treated with DP (relative risk, 4.0; 95% confidence interval [CI], 1.51–10.58; P = .0046). The cumulative risk of recurrence with P. vivax at 9 weeks was 79.1% (95% CI, 73.5%–84.8%) in patients treated with CQ compared with 54.9% (95% CI, 48.2%–61.6%) in those receiving DP (hazard ratio [HR], 2.27; 95% CI, 1.8–2.9; P < .001). Children <5 years old were at greater risk of recurrent P. vivax infection (74.4%; 95% CI, 63.2%–85.6%) than older patients (55.3% [95% CI, 50.2%–60.4%]; HR, 1.58 [95% CI, 1.1–2.2]; P = .005). In vitro susceptibility testing showed that 13% of the tested isolates had a CQ median inhibitory concentration >100 nmol/L, suggesting reduced susceptibility.
Conclusions. The efficacy of CQ in the treatment of P. vivax infections is declining on the Thai-Myanmar border. DP is an effective alternative treatment.
Clinical Trials Registration. ISRCTN87827353.
PMCID: PMC3193831  PMID: 22002979
17.  A Small Amount of Fat Does Not Affect Piperaquine Exposure in Patients with Malaria▿† 
Dihydroartemisinin-piperaquine is a new, highly effective, and well-tolerated combination treatment for uncomplicated falciparum malaria. The lipophilic characteristic of piperaquine suggests that administration together with fat will increase the oral bioavailability of the drug, and this has been reported for healthy volunteers. This pharmacokinetic study monitored 30 adult patients with uncomplicated falciparum malaria for 4.5 months to evaluate the effects of the concomitant intake of fat on the total piperaquine exposure. The fixed-drug combination of dihydroartemisinin-piperaquine was given with water to fasting patients (n = 15) or was coadministered with 200 ml milk containing 6.4 g fat (n = 15). The drug combination was generally well tolerated, and there were no severe adverse effects reported for either group during the study. Total piperaquine exposure (area under the concentration-time curve from zero to infinity [AUC0-∞]; results are given as medians [ranges]) were not statistically different between fed (29.5 h · μg/ml [20.6 to 58.7 h · μg/ml]) and fasting (23.9 h · μg/ml [11.9 to 72.9 h · μg/ml]) patients, but the interindividual variation was reduced in the fed group. Overall, none of the pharmacokinetic parameters differed statistically between the groups. Total piperaquine exposure correlated well with the day 7 concentrations in the fasted group, but the fed group showed a poor correlation. In conclusion, the coadministration of 6.4 g fat did not have any significant effect on piperaquine pharmacokinetics in the treatment of uncomplicated malaria.
PMCID: PMC3165307  PMID: 21709087
18.  Pharmacokinetics of Amodiaquine and Desethylamodiaquine in Pregnant and Postpartum Women with Plasmodium vivax Malaria▿† 
In order to study the pharmacokinetic properties of amodiaquine and desethylamodiaquine during pregnancy, 24 pregnant women in the second and third trimesters of pregnancy and with Plasmodium vivax malaria were treated with amodiaquine (10 mg/kg of body weight/day) for 3 days. The same women were studied again at 3 months postpartum. Plasma was analyzed for amodiaquine and desethylamodiaquine by use of a liquid chromatography-tandem mass spectrometry method. Individual concentration-time data were evaluated using noncompartmental analysis. There were no clinically relevant differences in the pharmacokinetics of amodiaquine and desethylamodiaquine between pregnant (n = 24) and postpartum (n = 18) women. The results suggest that the current amodiaquine dosing regimen is adequate for the treatment of P. vivax infections during pregnancy.
PMCID: PMC3165320  PMID: 21709098
19.  An Open-Label Crossover Study To Evaluate Potential Pharmacokinetic Interactions between Oral Oseltamivir and Intravenous Zanamivir in Healthy Thai Adults▿† 
There is no parenteral formulation of the neuraminidase inhibitor oseltamivir, the most widely used anti-influenza virus drug. Oseltamivir resistance is an increasing problem. Zanamivir is effective against the most prevalent oseltamivir-resistant influenza viruses. A parenteral formulation of zanamivir is in development for the treatment of severe influenza. It is not known if there is any pharmacokinetic interaction between the two drugs. Sixteen healthy Thai adult volunteers were studied in an open-label, four-period, randomized two-sequence crossover pharmacokinetic study in which zanamivir was given by constant-rate infusion or slow intravenous injection either alone or together with oral oseltamivir. Plasma concentration profiles of oseltamivir, the active metabolite oseltamivir carboxylate, and zanamivir were measured by liquid chromatography-mass spectrometry-mass spectrometry. Both drugs were well tolerated alone and in combination. The maximum plasma concentrations and the areas under the plasma concentration-time curves (AUC) of oseltamivir and oseltamivir carboxylate were not significantly different when oseltamivir was given separately or together with zanamivir. Maximum plasma concentrations of zanamivir were 10% (95% confidence interval, 7 to 12%) higher when zanamivir was infused concurrently with oral oseltamivir than with infusions before or after oral oseltamivir. The plasma zanamivir total AUC was positively correlated with the total oseltamivir carboxylate AUC (Pearson's correlation coefficient [rP] = 0.720, P = 0.002, n = 16) but not with the oseltamivir AUC (rp = 0.121, n = 16). There is no clinically significant pharmacokinetic interaction between oseltamivir and zanamivir.
PMCID: PMC3165358  PMID: 21690287
20.  Estimation of gestational age from fundal height: a solution for resource-poor settings 
Many women in resource-poor settings lack access to reliable gestational age assessment because they do not know their last menstrual period; there is no ultrasound (US) and methods of newborn gestational age dating are not practised by birth attendants. A bespoke multiple-measures model was developed to predict the expected date of delivery determined by US. The results are compared with both a linear and a nonlinear model. Prospectively collected early US and serial symphysis-pubis fundal height (SFH) data were used in the models. The data were collected from Karen and Burmese women attending antenatal care on the Thai–Burmese border. The multiple-measures model performed best, resulting in a range of accuracy depending on the number of SFH measures recorded per mother (for example six SFH measurements resulted in a prediction accuracy of ±2 weeks). SFH remains the proxy for gestational age in much of the resource-poor world. While more accurate measures should be encouraged, we demonstrate that a formula that incorporates at least three SFH measures from an individual mother and the slopes between them provide a significant increase in the accuracy of prediction compared with the linear and nonlinear formulae also using multiple SFH measures.
PMCID: PMC3262426  PMID: 21849388
symphysis-fundal height; gestational age; estimation; formula; ultrasound
21.  Quantification of the anti-influenza drug zanamivir in plasma using high-throughput HILIC–MS/MS 
Bioanalysis  2011;3(2):157-165.
Parenteral zanamivir is a promising drug for the treatment of severe influenza. However, quantification of this polar drug in biological matrices has traditionally been difficult and the methods developed have been relatively insensitive.
A high-throughput bioanalytical method for the ana lysis of zanamivir in human plasma using SPE in the 96-well plate format and LC coupled to positive MS/MS has been developed and validated according to US FDA guidelines. The method uses 50 μl of plasma and covers a large working range from 1–50, 000 ng/ml with a LOD of 0.50 ng/ml.
This new LC–MS/MS assay is more sensitive than previous methods despite using a small plasma volume sample. It is particularly suitable for clinical studies on both parenteral and inhaled zanamivir.
PMCID: PMC3096760  PMID: 21250845
22.  Are there any changes in burden and management of communicable diseases in areas affected by Cyclone Nargis? 
This study aims to assess the situation of communicable diseases under national surveillance in the Cyclone Nargis-affected areas in Myanmar (Burma) before and after the incident.
Monthly data during 2007, 2008 and 2009 from the routine reporting system for disease surveillance of the Myanmar Ministry of Health (MMOH) were reviewed and compared with weekly reporting from the Early Warning and Rapid Response (EWAR) system. Data from some UN agencies, NGOs and Tri-Partite Core Group (TCG) periodic reviews were also extracted for comparisons with indicators from Sphere and the Inter-Agency Standing Committee.
Compared to 2007 and 2009, large and atypical increases in diarrheal disease and especially dysentery cases occurred in 2008 following Cyclone Nargis. A seasonal increase in ARI reached levels higher than usual in the months of 2008 post-Nargis. The number of malaria cases post-Nargis also increased, but it was less clear if this reflected normal seasonal patterns or was specifically associated with the disaster event. There was no significant change in the occurrence of other communicable diseases in Nargis-affected areas. Except for a small decrease in mortality for diarrheal diseases and ARI in 2008 in Nargis-affected areas, population-based mortality rates for all other communicable diseases showed no significant change in 2008 in these areas, compared to 2007 and 2009. Tuberculosis control programs reached their targets of 70% case detection and 85% treatment success rates in 2007 and 2008. Vaccination coverage rates for DPT 3rd dose and measles remained at high though measles coverage still did not reach the Sphere target of 95% even by 2009. Sanitary latrine coverage in the Nargis-affected area dropped sharply to 50% in the months of 2008 following the incident but then rose to 72% in 2009.
While the incidence of diarrhea, dysentery and ARI increased post-Nargis in areas affected by the incident, the incidence rate for other diseases and mortality rates did not increase, and normal disease patterns resumed by 2009. This suggests that health services as well as prevention and control measures provided to the Nargis-affected population mitigated what could have been a far more severe health impact.
PMCID: PMC3135519  PMID: 21708044
23.  Chloroquine resistant vivax malaria in a pregnant woman on the western border of Thailand 
Malaria Journal  2011;10:113.
Chloroquine (CQ) resistant vivax malaria is spreading. In this case, Plasmodium vivax infections during pregnancy and in the postpartum period were not satisfactorily cleared by CQ, despite adequate drug concentrations. A growth restricted infant was delivered. Poor susceptibility to CQ was confirmed in-vitro and molecular genotyping was strongly suggestive of true recrudescence of P. vivax. This is the first clinically and laboratory confirmed case of two high-grade CQ resistant vivax parasite strains from Thailand.
PMCID: PMC3112451  PMID: 21545737
24.  Spatio-temporal patterns of malaria infection in Bhutan: a country embarking on malaria elimination 
Malaria Journal  2011;10:89.
At the verge of elimination of malaria in Bhutan, this study was carried out to analyse the trend of malaria in the endemic districts of Bhutan and to identify malaria clusters at the sub-districts. The findings would aid in implementing the control activities. Poisson regression was performed to study the trend of malaria incidences at district level from 1994 to 2008. Spatial Empirical Bayesian smoothing was deployed to identify clusters of malaria at the sub-district level from 2004 to 2008.
Trend of the overall districts and most of the endemic districts have decreased except Pemagatshel, which has an increase in the trend. Spatial cluster-outlier analysis showed that malaria clusters were mostly concentrated in the central and eastern Bhutan in three districts of Dagana, Samdrup Jongkhar and Sarpang. The disease clusters were reported throughout the year. Clusters extended to the non-transmission areas in the eastern Bhutan.
There is significant decrease in the trend of malaria with the elimination at the sight. The decrease in the trend can be attributed to the success of the control and preventive measures. In order to realize the target of elimination of malaria, the control measure needs to be prioritized in these high-risk clusters of malaria.
PMCID: PMC3094227  PMID: 21496285
25.  Plasmodium vivax Recurrence Following Falciparum and Mixed Species Malaria: Risk Factors and Effect of Antimalarial Kinetics 
On the Thai-Myanmar border, Plasmodium vivax is the most common cause of parasitological failure following treatment for acute falciparum malaria. Slowly eliminated antimalarials significantly reduce the risk of early recurrence.
(See editorial commentary by Baird, on pages 621–623.)
Background. Plasmodium vivax malaria commonly follows treatment of falciparum malaria in regions of co-endemicity. This is an important cause of preventable morbidity.
Methods. We examined the factors contributing to the risk of recurrence of P. vivax infection after treatment of acute falciparum malaria in a series of clinical trials conducted on the Thai-Myanmar border from 1991 through 2005.
Results. Overall, 10,549 patients (4960 children aged <15 years and 5589 adults) were treated for falciparum malaria; of these patients, 9385 (89.0%) had Plasmodium falciparum monoinfection and 1164 (11.0%) had mixed P. falciparum/P. vivax infections according to microscopic examinations performed at screening. The cumulative proportion of patients with P. falciparum infection recurrence by day 63 was 21.5% (95% confidence interval [CI], 20.3%–22.8%), and the cumulative proportion with P. vivax infection recurrence was 31.5% (95% CI, 30.1%–33.0%). Significant risk factors for P. vivax infection recurrence were mixed infection at enrollment, male sex, younger age, lower hematocrit, higher asexual P. falciparum parasite density (P < .001 for all factors), and P. falciparum gametocytemia at enrollment (P = .001). By day 63, the cumulative risk of vivax malaria after P. falciparum monoinfection was 51.1% (95% CI, 46.1%–56.2%) after treatment with rapidly eliminated drugs (t1/2 <1 day), 35.3% (95% CI, 31.8%–39.0%) after treatment with intermediate half-life drugs (t1/2 1–7 days), and 19.6% (95% CI, 18.1%–21.3%) after treatment with slowly eliminated drugs (t1/2 > 7 days) (P < .001, by test for trend). Artemisinin-based combinations containing mefloquine or piperaquine, compared with the artemether-lumefantrine and artesunate-atovaquone-proguanil combinations, were associated with a 3.6-fold to 4.2-fold lower adjusted hazard ratio for P. vivax infection recurrence within 63 days after pure or mixed P. falciparum infections (P < .001, for comparisons with artesunate-mefloquine).
Conclusions. On the Thai-Myanmar border, P. vivax is the most common cause of parasitological failure after treatment for falciparum malaria. Slowly eliminated antimalarials reduce the risk of early P. vivax infection recurrence.
PMCID: PMC3060895  PMID: 21292666

Results 1-25 (60)