An open randomized clinical trial of Artekin vs artesunate-mefloquine in the treatment of acute uncomplicated falciparum malaria.

Malaria remains a major cause of morbidity and mortality in tropical countries and subtropical regions in the world. Southeast Asia has the most resistant malaria parasites in the world, which has limited treatment options in this region. In response to this situation, short-course artemisinin-based combination therapies (ACTs) have been developed. The combination of dihydroartemisinin (DHA) and piperaquine (PQP) in the form of Artekin has been developed as an alternative to established combinations, such as artesunate-mefloquine, primarily to reduce treatment costs and toxicity. We conducted a study comparing a standard treatment for acute uncomplicated falciparum malaria (artesunate 4 mg/kg/day together with mefloquine 8 mg/kg/day oral route once a day for 3 days) (Group A) and a combination of dihydroartemisinin 40 mg and piperaquine 320 mg in the form of Artekin given once a day for 3 days (Group B) to determine safety, efficacy, and tolerability. One hundred and eighty patients were randomly enrolled at the ratio of 1:2 into groups A:B. All patients had rapid initial clinical and parasitological responses. There were no significant differences in fever clearance time or parasite clearance time between both groups. The 28-day cure rates were high, at 100% and 99%, in groups A and B, respectively. We conclude that Artekin was as effective and well-tolerated as artesunate-mefloquine, and can be used alternatively as the current treatment for multidrug-resistant P. falciparum malaria.

An open, randomized trial of three-day treatment with artesunate combined with a standard dose of mefloquine divided over either two or three days, for acute, uncomplicated falciparum malaria.

The combination of artesunate and mefloquine is currently one of the most effective treatments for multidrug-resistant Plasmodium falciparum malaria. Simultaneous, rather than sequential treatment with the two drugs, would allow better patient compliance. We therefore evaluated three-day treatment with artesunate combined with either 2 or 3 days of mefloquine co-administered once a day with artesunate. The study was an open, randomized trial for acute, uncomplicated falciparum malaria and was conducted at the Bangkok Hospital for Tropical Diseases. One hundred and twenty adult patients were randomized to two treatment groups. Group 1 patients received 4 mg/kg/day of artesunate for 3 days and 3 daily doses of 8.0 mg/kg/day mefloquine given with artesunate. Group 2 patients received the same dose of artesunate and the same total dose of mefloquine (25 mg/kg). However, the mefloquine was given as 15 mg/kg on the first day and 10 mg/kg/ on the second day, again with artesunate. The baseline demographic and clinical characteristics of the patients in the two groups were similar. The cure rates for the 3-day and 2-day mefloquine regimens were 100% and 99%, respectively. There were no significant differences in either median fever clearance times (group 1=32 hours; group 2=33 hours) or mean parasite clearance times (group 1=42.3 hours; group 2=43.3 hours). Both regimens were well tolerated and there were no significant differences in the incidence of adverse effects. Nausea or vomiting occurred in 3.8% of patients in both groups and transient dizziness occurred in 4% of group 1 and 9% of group 2 patients. These results suggest that a 3-day regimen of mefloquine administered with artesunate is effective and well tolerated. This practical regimen could improve patient compliance.

The pharmacokinetics of oral dihydroartemisinin and artesunate in healthy Thai volunteers.

The pharmacokinetics of oral dihydroartemisinin (DHA) following the dose of 2 and 4 mg/ kg body weight dihydroartemisinin (Twisinin, T-2 Program, Thailand) and 4 mg/kg body weight oral artesunate (AS; Guilin Pharmaceutical Works, Guangxi, China) were investigated in 20 healthy Thai volunteers (10 males, 10 females). All formulations were generally well tolerated. Oral DHA was rapidly absorbed from gastrointestinal tract with marked inter-individual variation. The pharmacokinetics of DHA following the two dose levels were similar and linearity in its kinetics was observed. Based on the model-independent pharmacokinetic analysis, median (95% CI) values for Cmax of 181 (120-306) and 360 (181-658) ng/ml were achieved at 1.5 hours following 2 and 4 mg/kg body weight dose, respectively. The corresponding values for AUC0-infinity, t1/2z, CL/f and Vz/f were 377 (199-1,128) vs 907 (324-2,289) ng.h/ml, 0.96 (0.70-1.81) vs 1.2 (0.75-1.44) hours, 7.7 (4.3-12.3) vs 6.6 (3.1-10.1) l/kg, and 90.5 (28.6-178.2) vs 6.6 (3.1-10.1) ml/min/kg, respectively (2 vs 4 mg/kg dose). Oral AS was rapidly biotransformed to DHA, which was detectable in plasma as early as 15 minutes of AS dosing. Following 4 mg/kg dose, median (95% CI) value for Cmax of 519 (236-284) ng/ml was achieved at 0.7 (0.25-1.5) hours. AUC0-infinity, and t1/2z were 657 (362-2,079) ng.h/ml, 0.74 (0.34-1.42) hours, respectively. Cmax of DHA following oral AS were significantly higher, but total systemic exposure was greater following oral DHA at the same dose level (4 mg/kg body weight). There was no significant sex difference in pharmacokinetics of DHA.

Therapeutic efficacy of artesunate in Plasmodium vivax malaria in Thailand.

Our previous study showed that in vitro susceptibility of Plasmodium vivax to chloroquine has significantly decreased in Thailand within the past two decades. Thus, the evaluation of alternative antimalarials for treatment of vivax malaria is needed. The aim of this study was to examine parasitological and clinical efficacy of an artemisinin derivative (artesunate) for the treatment of vivax malaria in patients who were admitted to the Bangkok Hospital for Tropical Diseases. We randomly allocated patients aged 12-56 years to receive 3.3mg/kg (adult dose 200 mg) on the first day, and for the next four days each patient was given 1.65 mg/kg orally (adult dose 100 mg), total dose = 600 mg. After the five-day course of artesunate, primaquine was given: a single oral dose of 15mg for 14 days. A total number of 42 patients received treatment. All participants were followed up for 28 days. In all the cases, both parasitemia and fever were resolved rapidly; the mean fever clearance time and parasite clearance time, 14.6 and 36.7 hours, respectively, showed that therapeutic response to artesunate was better than that of chloroquine. The 14-day cure rate was 100%, but reappearance of parasitemia was seen in two patients on days 21 and 25 following treatment, respectively. These two cases of failure rate should be considered as true relapse rather than recrudescence, since the relapse interval in Southeast Asian vivax malaria according to recent findings seems to be 3 weeks after start of treatment, if primaquine is not given or an inadequate amount is given. In conclusion, artesunate might be useful in treatment of vivax malaria, causing a good blood schizontocidal effect. However, to prevent emerging resistance it should never be used alone.

Monitoring the therapeutic efficacy of antimalarials against uncomplicated falciparum malaria in Thailand.

Increasing antimalarial drug-resistance is an important problem in Thailand. The results of monitoring the antimalarial efficacy are used in decision-making about using antimalarials to treat uncomplicated falciparum malaria in Thailand. In 2002, 552 patients with uncomplicated malaria were treated according to the Thai National Drug Policy, with mefloquine 25 mg/kg plus artesunate 12 mg/kg and primaquine 30 mg in divided doses for 2 days in high-mefloquine-resistant areas; mefloquine 15 mg/kg plus primaquine 30 mg in non- or low-mefloquine-resistant areas; mefloquine 15 mg/kg plus artesunate 12 mg/kg and primaquine 30 mg in divided doses for 2 days or Coartem (6-dose regimen for adult contains 480 mg artemether and 2880 mg lumefantrine) plus primaquine 30 mg given over 3 days in moderate-mefloquine-resistant areas. The study shows that mefloquine, artesunate plus mefloquine, and artemether plus lumefantrine are effective in the treatment of uncomplicated malaria in most areas of Thailand except for Ranong and Kanchanaburi, where the first-line treatment regimen should be revised.

Comparative clinical trial of two-fixed combinations dihydroartemisinin-napthoquine-trimethoprim (DNP) and artemether-lumefantrine (Coartem/Riamet) in the treatment of acute uncomplicated falciparum malaria in Thailand.

An open randomized comparison of two-fixed dose artemisinin derivative-containing combination regimens was conducted in adults with acute uncomplicated multidrug resistant falciparum malaria in Thailand. DNP, a combination of dihydroartemisinin with napthoquine and trimethoprim developed recently in China, has been evaluated in China, Vietnam, Cambodia and Thailand. This study was performed to compare the safety, tolerability and efficacy of DNP and artemether-lumefantrine/Coartem. One hundred and thirty eligible uncomplicated falciparum malaria patients were enrolled into the study. Patients were randomly assigned in a 2:1 ratio into group A, which received DNP one tablet twice a day for one day; and group B, which received Coartem/Riamet four tablets twice a day for 3 days. The cure rates at 28-day were 99% and 97% in group A and group B, respectively. No serious adverse events occurred. We concluded that both DNP and Coartem/ Riamet were safe, well tolerated and highly efficacious in the treatment of acute uncomplicated falciparum malaria in Thailand.

Mapping soil-transmitted helminths in Southeast Asia and implications for parasite control.

Establishing the current status and distribution of soil-transmitted helminths is essential for developing and implementing parasite control. Although Southeast Asia is known to have a high prevalence of infection, a precise estimate of the total disease burden has not been fully described. Here, we use Geographical Information Systems (GIS) to collate and map recent published surveys on soil-transmitted helminth epidemiology and distribution for this region. Distinct geographical variation was observed, which is suggested to reflect climatic variation, as well as behavioral differences. However, for much of the region few data are available, and therefore it proved necessary to generate predictions of the distribution of soil-transmitted helminths using remotely sensed (RS) satellite sensor environmental variables. A significant finding was the importance of land surface temperature in influencing the distribution of Ascaris lumbricoides and Trichuris trichiura. Spatial analyses using RS satellite sensor data were then used to generate predictive maps of infection risk. This information provided the basis for an estimate of the population at risk of infection and the numbers requiring treatment. These applications of GIS and remote sensing provide a good basis for developing control of soil-transmitted helminths in the region.

An open randomized clinical trial of Artecom vs artesunate-mefloquine in the treatment of acute uncomplicated falciparum malaria in Thailand.

The efficacy and safety of Artecom were assessed in an open randomized trial in adults presenting with acute, uncomplicated Plasmodium falciparum malaria in Thailand. Three hundred and fifty-two patients were randomly enroled at the ratio of 2:1 into group A:B and received Artecom (group A) and the standard combination of artesunate and mefloquine (group B) respectively. All patients had rapid initial clinical and parasitological responses. There were no significant differences in fever clearance time and parasite clearance time between the two groups. The 28-day cure rates were high as 97% in both groups. Artecom was effective and well-tolerated as artesunate-mefloquine, the current treatment in this area of multidrug-resistant P. falciparum malaria.

A comparative clinical trial of combinations of dihydroartemisinin plus azithromycin and dihydroartemisinin plus mefloquine for treatment of multidrug resistant falciparum malaria.

With the deteriorating situation of multidrug resistant falciparum malaria, a new drug or drugs in combinations are urgently needed. We conducted a study comparing a combination of dihydroartemisinin 240 mg and mefloquine 1,250 mg given over 3 days (Group 1) and a combination of dihydroartemisinin 240 mg and azithromycin 1,500 mg given over 3 days (Group 2), to determine safety, efficacy and tolerability. All of the patients stayed in a non-malaria endemic area during the study. By the third day after drug administration, most patients were free of parasites and none had serious adverse events. The cure rates at day 28 were 100% and 69.7% in Group 1 and Group 2, respectively (p<0.01). We conclude that a combination of dihydroartemisnin and azithromycin was safe and effective and may be another interesting regimen of the treatment of uncomplicated multidrug resistant Plasmodium falciparum malaria in Thailand.

Plasmodium vivax malaria in Southeast Iran in 1999-2001: establishing the response to chloroquine in vitro and in vivo.

Chloroquine-resistant Plasmodium vivax is emerging in Oceania, Asia and Latin America. The drug sensitivity of P. vivax to chloroquine both in vivo and in vitro in the southern part of Iran was assessed; chloroquine-resistant Plasmodium falciparum has already been documented in this area. The in vitro sensitivity of 39 P. vivax isolates was assessed: the mean IC50 and IC90 were 189 ng/ml and 698 ng/ml blood respectively; for in vivo testing, all 39 vivax malaria patients were treated with a standard regimen of chloroquine and followed-up at 28 days: the mean parasite clearance time was 67.2 +/- 22.5 hours. The in vitro development of young parasites to mature schizonts in standard test medium was compared with that obtained in McCoy's 5A medium: no significant difference was observed. Synchronization of the blood-stage parasites was performed according to Lambros' method: the method was not suitable because it was detrimental to the parasites. A number of in vitro tests were performed using both our own laboratory-predosed microplates and WHO microplates: there was no significant difference between the results.

A cross-sectional study of intestinal parasitic infections among schoolchildren in Nan Province, Northern Thailand.

A cross-sectional study of the prevalence of intestinal parasitic infections at eight schools in Bo Klau district and four schools in Chalerm Prakiet district, Nan Province, in January and February, 2001. A total of 1,010 fecal samples were examined using the formalin-ether sedimentation technique. Results revealed that the rate of helminthic infection was 60.0%, while protozoa accounted for 36.2% of infections; mixed infections were common, resulting in a total prevalence of both parasites of 68.1%. Helminthic parasites, listed by frequency of infections, were Ascaris lumbricoides (21.7%), hookworm (18.5%), Trichuris trichiura (16.3%), Opisthorchis viverrini (1.7%), Strongyloides stercoralis (0.9%) and Enterobius vermicularis (0.9%). The protozoal infections were Entamoeba coli (25.8%), Giardia lamblia (5.3%), Endolimax nana (2.5%), Entamoeba histolytica (1.4%), Blastocystis hominis (0.8%), Chilomastix mesnili (0.3%) and Iodamoeba bütschlii (0.1%). This study emphasizes the need for improved environmental hygiene ie clean water supplies and enhanced sanitation, in affected communities. Health promotion, by means of a school-based educational approach is recommended; regular check-ups should be implemented, and a continuos program of treatment should be considered.

Effect of primaquine standard dose (15 mg/day for 14 days) in the treatment of vivax malaria patients in Thailand.

Primaquine (8-aminoquinoline), the only effective drug to prevent relapses of the persistent liver forms of Plasmodium vivax and Plasmodium ovale, can induce hemolytic anemia in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency. The severity varies considerably among affected individuals. Three hundred and sixty-four Plasmodium vivax cases (342 G6PD-normal and 22 G6PD-deficient) were given a 3-day course of chloroquine (total dose 1,500 mg) followed by primaquine 15 mg a day for 14 days and completed a 28-day follow-up. All G6PD-deficient patients were male; there were no relapses or serious adverse events during the study. Although a significant decrease in hematocrit levels and an increase in the percent reduction of hematocrit levels were observed on day 7 (34.9+/-5.0 vs 26.7+/-5.4; (-1.2)+/-14.4 vs (-24.5) +/-13.9 respectively) and on day 14 (35.7+/-4.3 vs 30.9+/-3.1; 1.6+/-17.8 vs (-11.0) +/-19.3 respectively) blood transfusion was not required. Daily doses of 15 mg of primaquine for 14 days following a full course of chloroquine when prescribed to Thai G6PD deficient patients where Mahidol variant is predominant, are relatively safe.

IgE elevation and anti-plasmodium falciparum IgE antibodies: association of high level with malaria resistance.

The total IgE and anti-Plasmodium falciparum IgE antibodies were determined by enzyme linked immunosorbent assay (ELISA) in 480 children and adults living in malaria endemic area along Thai-Myanmar border, Kanchanaburi Province, western Thailand. Approximately 73.13% of tested individuals had elevated levels of total IgE with a range of 160-998 ng/ml. 20.5% of these IgE were specific to P falciparum blood stage antigens, with a range of 78-353 microg/ml. However, the levels of total IgE were not significantly correlated with those of specific IgE (r = 0.083). The elevation of anti-P falciparum IgE antibodies seems to be age dependent. The prolonged or repeated exposure to malaria parasites is necessary for the induction of specific IgE response as indicated by the finding of a significant correlation between the levels of P falciparum specific IgE and the number of malaria attacks (r = 0.551, p = 0.01). Interestingly, among the specific IgE responders, 20 individuals naturally exposed to malaria but without clinical malaria reported had high levels of both total IgE and anti- P. falciparum IgE antibodies, with mean values of 418.67 mg/ml and 146.25 ng/ml, respectively. It is likely that the antibodies from such specific IgE responders could mediate phagocytosis in vitro.

Clinical trial of halofantrine with modified doses for treatment of malaria in the hospital for tropical diseases.

The spread of falciparum malaria resistant to chloroquine all over Southeast Asian continent has led to increasing use of alternative antimalarial drugs. Halofantrine has been shown to be effective against multidrug resistant Plasmodium falciparum. One hundred and twenty falciparum malaria cases were randomly assigned to one of three different halofantrine regimes. Group I (HA1) received 500 mg three times daily for 3 days (total dose: 4,500 mg), group II (HA2) received 500 mg three times daily for the first and the third day (total dose: 3,000 mg) and group III (HA3) received 500 mg three times for one day followed by 500 mg once daily for 7 days (total dose: 4,500 mg). No significant difference in the cure rate was observed among the three regimes (cure rate: 89%, 73%, 97% respectively). However, the cure rate was significantly higher in the HA3 group when compared to the HA2 group. There were no overt cardiac problems seen in this study. Thus, halofantrine has high efficacy in the recommended treatment dose of 500 mg three times after meals on the first day followed by 500 mg once a day after a meal for 7 days (total dose: 4,500 mg).

Lack of association between CSF nitrate and sera nitrate in falciparum malaria infection.

Nitrate levels in CSF and sera from 16 coma and 19 noncoma falciparum malaria patients were determined using nitric oxide colorometric assay. The medians (range lower, upper limits) of nitrate in sera of comatose and noncomatose patients were 0.28 (0.11, 1.24) and 0.23 (0.05, 0.87) microM, respectively. The medians of nitrate level in CSF of coma and noncoma cases were 0.09 (0.01, 0.28) and 0.15 (0, 1.18) microM, respectively. There was no difference of nitrate level in sera and CSF from comatose or noncomatose patients compared to that in normal sera and CSF. The amount of nitrate in sera and CSF of both groups was not significantly correlated with coma depth, parasitemia, parasite clearance time and time to recovery. Contrast to our in vitro study using immunoperoxidase staining, we found inducible nitric oside synthase production by brain endothelial cells during 4-24 hours of coculturing with late stage of P. falciparum infected red blood cells. These results suggests that malaria severity can not be differentiated by nitrate level in body fluid.

Natural human IgG subclass antibodies to Plasmodium falciparum blood stage antigens and their relation to malaria resistance in an endemic area of Thailand.

The immunoglobulin G (IgG) subclass antibodies to Plasmodium falciparum blood stage antigens in the sera of 181 individuals living in malaria endemic area in Kanchanaburi Province, western Thailand, were determined by enzyme-linked immunosorbent assay (ELISA). In this study, IgG3 and IgG1 were shown to be the predominant subclasses. Generally, IgG2 were coexpressed with IgG1 and IgG3 while IgG4 was found to coexpress with other three IgG subclasses. The levels of specific IgG1, IgG2, and IgG3 increased significantly with age (r = 0.295, p = 0.000; r = 0.416, p = 0.000; r = 0.320, p = 0.000, respectively). The data indicate that the higher antibody production required continuous stimulation under natural condition. Furthermore, the levels of specific IgG1, IgG2 and IgG3 increased in immune individuals without clinical malaria, reported in adolescents and adults, were associated with malaria resistance. Similar results were found in children with different patterns of IgG subclasses in which the specific IgG2 and IgG3, but not IgG1 was related to resistance.

Frequency of early rising parasitemia in falciparum malaria treated with artemisinin derivatives.

To define the frequency of the early rising of parasitemia in falciparum malaria patients treated with artemisinin derivatives, a retrospective chart review of 497 patients admitted to the Hospital for Tropical Diseases, Bangkok in 1996 was carried out. Early rising parasitemia, defined as an increase in the parasite count over the baseline pretreatment level during the first 24 hours of treatment, was found in 59/229 episodes (25.8%) of uncomplicated, and 111/268 episodes (41.3%) of complicated falciparum malaria. All uncomplicated cases were successfully treated without developing any complications. There were 2 deaths and 13 changes of drug regimen in the complicated group. Only one of these unfavorable responses was due to parasite response. Early rising parasitemia was very common in falciparum malaria treated with artemisinin derivatives, despite their ability to clear the parasitemia, and did not indicate failure of the drug used.

Evaluation of a newly developed dipstick test for the rapid diagnosis of scrub typhus in febrile patients.

Scrub typhus is a potentially fatal, febrile disease prevalent in rural Asia. The etiological agent, Orientia tsutsugamushi, is transmitted to humans by the bite of a larval trombiculid mite. No current diagnostic test is sufficiently practical for use by physicians working in rural areas. A new dipstick test using a dot blot immunoassay format has been developed for the serodiagnosis of scrub typhus. We evaluated this test on 83 patients presenting with acute fever of unknown origin at Maharaj Hospital, a tertiary care medical center in Nakhon Ratchasima, Northeast Thailand. The diagnosis of scrub typhus was confirmed in 30 of these patients (36%) by the indirect immunoperoxidase test. The sensitivity of the test was 87% and its specificity was 94%. The dot blot immunoassay dipstick is accurate, rapid, easy to use, and relatively inexpensive. It appears to be the best currently available test for diagnosing scrub typhus in rural areas where this disease predominates.

Can treatment of P. vivax lead to a unexpected appearance of falciparum malaria?

Of 994 patients admitted to the Bangkok Hospital for Tropical Diseases for P. vivax malaria, 104 (10.5%) experienced appearance of Plasmodiumfalciparum following drug treatment for P. vivax . In all patients, P. falciparum parasites were not found by microscopic examination upon admission. The mean time for P. falciparum appearance was 12.6 days after the commencement of chloroquine treatment. Patients experiencing appearance of P. falciparum had significantly lower hematocrit, and greater initial P. vivax parasite counts. We use a mathematical model to explore the consequences of chloroquine treatment of such mixed infections. Both clinical results and features of the model suggest that such "hidden infections" may be quite common, and that the appearance of P. falciparum may be stimulated by treatment of P. vivax.