Characterization of "Yaa Chud" Medicine on the Thailand-Myanmar border: selecting for drug-resistant malaria and threatening public health

Multidrug-resistant Plasmodium falciparum malaria is a severe public health problem on the Thailand-Myanmar border. Many villagers buy packets of 4-5 mixed medicines ("yaa chud") from shops without medical assessment as their first-line malaria treatment. In 2000-2001 a local researcher purchased 50 yaa chud from 44 shops around Mae Sot, Thailand and Myawaddy, Myanmar (Burma), for his wife who was said to be pregnant with fever and drowsiness. The tablets/capsules were provisionally identified by appearance and active ingredients determined in a subset by using mass and atomic spectrometry. The most frequently detected active ingredients were acetaminophen (22%), chlorpheniramine (13.4%), chloroquine (12.6%), tetracycline/doxycycline (11.4%), and quinine (5.1%). Only seven bags contained potentially curative medicine for malaria. A total of 82% of the bags contained medicines contraindicated in pregnancy. Inappropriate, ineffective antimalarial drugs on the Thailand-Myanmar border are likely to increase malaria morbidity, mortality and health costs and engender the emergence and spread of antimalarial drug resistance.     

Prevalence of malaria and HIV coinfection and influence of HIV infection on malaria disease severity in population residing in malaria endemic area along the Thai–Myanmar border

The objective of the study is to investigate the prevalence of malaria and HIV coinfection and assess the effect of HIV coinfection on malaria disease severity in malaria patients from the endemic area of Thailand along the Thai–Myanmar border. Blood samples were collected from a total of 867 patients with malaria (all species and severity) who attended Mae Tao clinic for migrant workers, Tak Province during 2005–2007 (439 samples), 2008–2010 (273 samples), and 2011–2013 (155 samples). The average prevalence rate of malaria and HIV coinfected cases in this malaria endemic area of the country during the three periods was 1.85%. HIV coinfection was observed only in samples with mono-infection of Plasmodium falciparum or Plasmodium vivax, with similar proportions (0.81 vs. 1.04%). Patients’ admission parasite density, an indicator of disease severity, was significantly higher in cases with HIV coinfection observed during 2008–2010. Anemia was found at a significantly higher frequency in patients coinfected with malaria and HIV observed during 2005–2007 compared with those infected with malaria alone. No association was observed between malaria and HIV coinfection and gender, and infected malaria species during the three observation periods. Patients with malaria and HIV coinfection had a significantly lower hemoglobin level than those with malaria infection alone. In conclusion, the prevalence of malaria and HIV coinfection in population of the malaria endemic area along the Thai–Myanmar border is low. HIV coinfection tended to increase parasite density, an indicator of malaria disease severity.     

Clinical-parasitological response and in-vitro sensitivity of Plasmodium vivax to chloroquine and quinine on the western border of Thailand

This study was conducted during 2002-2004 at Mae Sot District, on the Thai-Myanmar border, an area of multidrug-resistant Plasmodium falciparum malaria. Sixty-two patients with P. vivax malaria were included in the study. All were randomized into two groups to receive a 3-day regimen of chloroquine or a 3-day regimen of quinine. Primaquine was given to patients in both groups for the elimination of hepatic stages. Results from the present study suggest that the standard regimen of chloroquine and a 3-day course of quinine at the dose regimens under investigation were very effective and well tolerated for the treatment of P. vivax malaria in this area. All patients responded well to both drug regimens; the cure rates with chloroquine or quinine, when given concurrently with the tissue schizontocidal drug primaquine, were virtually 100% within 28 days of follow-up. No significant correlations between parasite clearance time (PCT) or fever clearance time (FCT) and inhibitory concentration 50 (IC50) were found. Patients who had PCT < or = 24 h and those with PCT >24 h had comparable IC50 to chloroquine (alone and plus primaquine) and quinine, as well as similar concentrations of chloroquine/desethylchloroquine (in blood) or quinine (in plasma) at the investigated time points.     

Early treatment failure in severe malaria resulting from abnormally low plasma quinine concentrations

A patient admitted with severe Plasmodium falciparum malaria in western Thailand had an early treatment failure with quinine, despite full dosing. Plasma quinine concentrations were subtherapeutic. Abnormal quinine pharmacokinetics may explain sporadic reports of quinine treatment failures in severe malaria.     

Assessment of in vitro sensitivity of Plasmodium vivax fresh isolates

Objective

To compare the applicability of the SYBR Green-I assay with the standard schizont maturation assay, for determination of sensitivity of Plasmodium vivax (P. vivax) to chloroquine and a new antifolate WR 99210.

Methods

The study was conducted at Mae Tao Clinic for migrant workers, Tak Province during April 2009 to July 2010. A total of 64 blood samples (1 mL blood collected into sodium heparinized plastic tube) were collected from patients with mono-infection with P. vivax malaria prior to treatment with standard regimen of a 3-day chloroquine. In vitro sensitivity of P. vivax isolates was evaluated by schizont maturation inhibition and SYBR Green-I assays.

Results

A total of 30 out of 64 blood samples collected from patients with P. vivax malaria were successfully analyzed using both the microscopic schizont maturation inhibition and SYBR Green-I assays. The failure rates of the schizont maturation inhibition assay (50%) and the SYBR Green-I assay (54%) were similar (P=0.51). The median IC₁₀s, IC₅₀s and IC₉₀s of both chloroquine and WR99210 were not significantly different from the clinical isolates of P. vivax tested. Based on the cut-off of 100 nM, the prevalences of chloroquine resistance determined by schizont maturation inhibition and SYBR Green-I assays were 19 and 11 isolates, respectively. The strength of agreement between the two methods was very poor for both chloroquine and WR99210.

Conclusions

On the basis of this condition and its superior sensitivity, the microscopic method appears better than the SYBR Green-I Green assay for assessing in vitro sensitivity of fresh P. vivax isolates to antimalarial drugs.     

Levamisole inhibits sequestration of infected red blood cells in patients with falciparum malaria

BACKGROUND: Sequestration of infected red blood cells (iRBCs) in the microcirculation is central to the pathophysiology of falciparum malaria. It is caused by cytoadhesion of iRBCs to vascular endothelium, mediated through the binding of Plasmodium falciparum erythrocyte membrane protein-1 to several endothelial receptors. Binding to CD36, the major vascular receptor, is stabilized through dephosphorylation of CD36 by an alkaline phosphatase. This is inhibited by the alkaline phosphatase-inhibitor levamisole, resulting in decreased cytoadhesion. METHODS: Patients with uncomplicated falciparum malaria were randomized to receive either quinine treatment alone or treatment with a single 150-mg dose of levamisole as an adjunct to quinine. Peripheral blood parasitemia and parasite stage distribution were monitored closely over time. RESULTS: Compared with those in control subjects, peripheral blood parasitemias of mature P. falciparum parasites increased during the 24 h after levamisole administration (n=21; P=.006). The sequestration ratio (between observed and expected peripheral blood parasitemia) of early trophozoite and midtrophozoite parasites increased after levamisole treatment, with near complete prevention of early trophozoite sequestration and >65% prevention of midtrophozoite sequestration. CONCLUSION: These findings strongly suggest that levamisole decreases iRBC sequestration in falciparum malaria in vivo and should be considered as a potential adjunctive treatment for severe falciparum malaria. TRIAL REGISTRATION: Current Controlled Trials identifier: 15314870.     

Urinary and blood cadmium levels in relation to types of food and water intake and smoking status in a Thai population residing in cadmium-contaminated areas in Mae Sot

Human exposure to cadmium (Cd) produces a wide variety of toxic effects involving many organs and systems, but the kidney is the main organ affected among long-term Cd-exposed people. In the general population, the primary sources of Cd exposure are cigarette smoke and food (shellfish, offal and certain vegetables). The aims of the study were to investigate the association between urinary and blood Cd levels and personal habits relating to Cd intake (consumption of food stuff, water and tobacco smoking), levels of renal biomarkers in the urine or serum of 314 Thai subjects (85 males, 229 females) who resided in Cd-contaminated areas of Mae Sot District, Tak Province, Thailand. Based on the cut-off levels of 1 microg/g creatinine and 5 microg/l for urinary and blood Cd levels, respectively, nearly all subjects had urinary Cd levels lower than cut-off values for urine and blood (88.2 and 77.7%, respectively). Binary logistic backward stepwise regression analysis with five covariates (gender, residential areas, consumption of bamboo or chicken, and smoking status), and eight covariates (residential areas, consumption of beans, pork, fish or liver, types and sources of rice consumed and smoking status) best predicted urinary and blood Cd levels, respectively. For renal biomarkers, N-acetyl-beta-glucosaminidase (NAG) best predicted both urinary and blood Cd with good accuracy. A larger sample size with equal distribution of subjects with low (< 2 microg/g creatinine) and high (> 2 microg/g creatinine) urinary Cd levels should be studied to obtain the regression equation that would best predict Cd body burden.     

Distribution of mefloquine in the blood of Thai patients with acute uncomplicated falciparum malaria following administration of therapeutic doses of artesunate

Purpose  

The study objectives to investigate the distribution of the antimalarial drug mefloquine (MQ) in cellular and fluid blood compartments when given at therapeutic dosage with artesunate and to investigate an eventual association with the occurrence of treatment-related adverse events in Thai patients with acute uncomplicated falciparum malaria.     

The influence of CYP2A6 polymorphisms and cadmium on nicotine metabolism in Thai population

We investigated the influence of genetic, cadmium exposure and smoking status, on cytochrome P450-mediated nicotine metabolism (CYP2A6) in 182 Thai subjects after receiving 2 mg of nicotine gum chewing for 30 min. The urinary excretion of cotinine was normally distributed over a 2 h period (logarithmically transformed). Individuals with urinary cotinine levels in the ranges of 0.01–0.21, and 0.52–94.99 μg/2 h were categorized as poor metabolizes (PMs: 6.5%), and extensive metabolizers (EMs: 93.5%), respectively. The majority of EMs (45%) carried homozygous wild-type genotypes (CYP2A6*1A/*1A, CYP2A6*1A/*1B and CYP2A6*1B/*1B), whereas only 1% of PMs carried these genotypes. Markedly higher frequencies of EMs were also observed in all heterozygous defective genotypes including the null genotype (*4C/*4C; 1 subject).A weak but significant positive correlation was observed between total amounts of urinary cadmium excretion and total cotinine excretion over 2 h. Our study shows generally good agreement between CYP2A6 genotypes and phenotypes. Smokers accumulated about 3–4-fold higher mean total amounts of 2-h urinary cadmium excretion (127.5 ± 218.2 ng/2 h) than that of non-smokers (40.5 ± 78.4 ng/2 h). Among the smokers (n = 16), homologous wild-type genotype *1/*1 was significantly the predominant genotype (6/16) compared with other defective allele including *4C/*4C. In addition, 2 h urinary excretion of cotinine in smokers of all genotypes was significantly higher than non-smokers. The proportion of smokers who smoked more than 5 cigarettes/day was significantly higher in EMs in all CYP2A6 genotypes (n = 14) than in PMs (n = 0).     

Field evaluation of a simple fluorescence method for detection of viable Mycobacterium tuberculosis in sputum specimens during treatment follow-up

Simple tuberculosis (TB) treatment monitoring tools are needed. We assessed the performance of fluorescein-diacetate (FDA) smear microscopy for detection of viable Mycobacterium tuberculosis in sputum specimens (n = 288) of TB cases under treatment compared to culture (17.4% culture positivity). FDA sensitivity was moderate (83.7% [95% confidence interval {CI}, 70.3 to 92.6]), and specificity was low (66.1% [59.5 to 72.2]). The good negative predictive value (94.8% [90.1 to 97.8]) and negative likelihood ratio (0.2) suggest using this method to rule out treatment failure in settings without access to culture.