Antigenic diversity of Plasmodium vivax and their geographic distribution in Thailand

Fifty-eight monoclonal antibodies (MAbs) raised against the erythrocytic stages of Plasmodium vivax were selected for typing of 501 P. vivax isolates from different geographic locations throughout Thailand. Based on their reactivities in the indirect fluorescent antibody test, these MAbs were classified into five groups: group I MAbs showing generalized staining of all blood stages; group II MAbs reacting with merozoites and their organelles; group III MAbs reacting with the surface membrane of merozoites; Group V MAbs reacting with the surface membrane of trophozoites and schizonts; and group VII MAbs reacting with internal components of the parasites. Sixteen MAbs reacted with more than 95% of the isolates; the epitopes recognized by these MAbs were considered as being invariant. The remaining MAbs reacted with 30-90% of the isolates, and the epitopes recognized by these MAbs were regarded as being variable. The variant epitopes were associated with > 200-, 135-, and 100-kilodalton (kDa) molecules of all blood stages, the 95-kDa molecule on merozoite organelles, the 200-kDa molecule on the surface of trophozoites and schizonts, and the 85-kDa molecule of the parasite internal components. Antigenic diversity occurred among the P. vivax population in the endemic areas of Thailand and was shown to vary from place to place and was highest in the area with the highest rate of transmission along the Myanmar border in western Thailand and along the Cambodian border in eastern Thailand, including Trat (48.4%), Tak (41.7%), Chantaburi (36.5%), and Mae Hong Son (36.4%). Demonstration of antigenic diversity of P. vivax parasites signals a note of caution in the development of vaccines for vivax malaria. The vaccines should be directed against protective, conserved and not against variant epitopes.

Antigenic disparity of Plasmodium vivax causing initial symptoms and causing relapse

Relapse infections are an important obstacle to the successful treatment and control of Plasmodium vivax malaria, but little is known about the nature of the relapse. To provide insight into the antigenic disparity of the parasites causing initial clinical symptoms and causing relapse, a panel of 58 monoclonal antibodies (MAbs) against erythrocytic stages of Plasmodium vivax was tested by indirect fluorescent antibody test in five relapse cases. The initial and relapse strains from three patients (R3, R4, and R5) exhibited similar IFA reactivity with all MAbs tested, whereas the isolates from two relapse cases (R1 and R2) showed different patterns of reactivity and were seen only with 15 MAbs In case R1, different IFA reactivities were observed with 12 MAbs, nine of which reacted with the initial (RPV261) but not the relapse (RPV393) isolates, whereas the other three MAbs reacted only with the relapse isolates. With regards to the second relapse case (R2) in whom two relapses occurred, different IFA reactivities were demonstrated with seven MAbs that reacted only with the initial isolate (RPV 182) and with the isolate from the first relapse (RPV 240) but not with the isolate from the second relapse (RPV 300). The antibody responses from patients who developed primary clinical symptoms and relapse were detected by Western immunoblotting. In cases R3, R4 and R5, there was no difference in the spectrum of antigens from initial and relapse sera recognized by the antibodies. In contrast, in cases R1 and R2, the molecules recognized by antibodies in initial and relapse sera were markedly altered. In case R1, the series of molecules of P. vivax antigens recognized by initial (RPV 261) and relapse (RPV 393) sera were 21, 25, 31, 39, 42, 61, 95, 115, 200, > 200 kDa and 21, 24, 31, 35, 57, 75, 200, > 200 kDa, respectively. In case R2, the initial serum (RPV 182) recognized P. vivax antigens with molecular weights of 23, 30, 52, 57, 68, 75, 85, 95, 115, and 195 kDa while the first relapse (RPV 240) and the second relapse sera recognized P. vivax antigens with molecular weights of 23, 30, 52, 85, 95,115 kDa and 30, 57, 68, 75, 85,195 kDa, respectively.

Treatment of Opisthorchis viverrini and intestinal fluke infections with Praziquantel

The study was carried out from September to November 1997 in Phrae Province of northern Thailand. A total of 95 adult patients with Opisthorchis-like ova in their stools were randomly treated with two different manufactured Praziquantels. Group 1, consisting of 49 patients, received a single dose of 40 mg per kg Praziquantel manufactured by the Thai Government Pharmaceutical Organization. Group 2 (46 patients) received Biltricide at the same dosage. Haplorchis taichui, H. yokogawai, Echinostome spp., O. viverrini, Taenia saginata and Enterobius vermicularis were expelled in the stools after treatment. Minute intestinal flukes were detected in 64% of patients. O. viverrini was found in lower proportion of 17%. By formalin-ether concentration examination one stool specimen from each patient, the cure rate in both groups on the 30th day of treatment was 100%. The side effects of the two different Praziquantel treatments were mild with no significant difference. Praziquantel, regardless of its manufacture, proved effective against O. viverrini and other minute intestinal flukes (H. taichui, H. yokogawai and Echinostome spp).

Two doses of artemether/mefloquine or artesunate/mefloquine combination for multidrug resistant falciparum Malaria

Plasmodium falciparum in Southeast Asia is highly resistant to chloroquine, sulfadoxine/ pyrimethamine, quinine and even mefloquine. The use of two doses of short course artemether/mefloquine combination has been shown to be effective in a recent study. In the present study, we have assessed the efficacy of short course treatment with artesunate/mefloquine, in comparison with artemether/mefloquine in patients with multidrug resistant falciparum malaria. Ninety-nine Thai male patients who sought consultation at Makham Malaria Clinic, Chantaburi (eastern part of Thailand), were randomized to receive either the combination of artemether (150 and 100 mg; group A) or artesunate (150 and 100 mg; group B) with mefloquine (750 and 500 mg) at 24 hours apart. The follow-up was on days 1, 2, 7, 14, 21, 28, 35 and 42. Patients in both groups showed a rapid initial response to treatment; fever and parasite were cleared within 48 hours in 100 and 100% vs 91.8 and 96%, for group A vs B, respectively. All patients in group A had completed the 42 day-follow up; however, two patients in group B did not finish the 42-day follow-up. The cure rate was 100% in either group. No serious adverse effects were found. Artemether or artesunate with mefloquine given two doses at 24 hours apart can be used as effective alternative treatment regimens for multidrug resistant falciparum malaria.

Effect of artemether on electrocardiogram in severe falciparum malaria

The effect of intramuscular artemether (intramuscular loading dose of 160 mg, followed by 80 mg daily for another 6 doses), in comparison with that of quinine (intravenous infusion of loading dose of 20 mg/kg, followed by 10 mg/kg q 8 hourly for 7 days), on the electrocardiograph of severe falciparum malaria patients were investigated in 102 Thai patients (92 males, 10 females) admitted to Pra Pokklao Hospital, Chantaburi, southeast of Thailand. Fifty patients (19 with quinine and 31 with artemether) were eligible for ECG analysis. Hypotension was found significantly more common in the quinine group (13 vs 2 cases). Thirteen, 5 and 1 patients with quinine treatment, respectively, had tachycardia, non-specific T-wave change and QTc prolongation. No significant dysrhythmia was found despite high plasma quinine concentrations. Five patients died; their ECGs were not significantly different from those who survived. In the group with intramuscular artemether, 17 cases had tachycardia prior to artemether treatment. QTc prolongation and non-specific T-wave change were found in 2 and 6 cases. One patient had RBBB and second degree AV-block on Day 1, but returned to normal on Day 2. No other dysrhythmia or other significant changes in ECG tracing which would suggest any effect of artemether on cardiovascular system were observed.

Opisthorchis viverrini infection in Thailand: studies on the morbidity of the infection and resolution following praziquantel treatment

A community study on opisthorchiasis was conducted in Prachinburi Province in eastern Thailand during 1990-1992. The morbidity from opisthorchiasis in the community and reversibility of biliary pathology following treatment with praziquantel at a single dose of 40 mg/kg were assessed by longitudinal investigations of clinical, laboratory, and ultrasonographic changes. A total of 913 voluntary subjects infected with Opisthorchis viverrini were randomly selected for longitudinal study, and 579 subjects without liver fluke infection were recruited as controls. The majority of the study group suffered from mild and moderate infections that were associated with nonspecific gastrointestinal symptoms. Grade I and II ultrasonographic changes, which indicated chronic inflammation of the biliary tract and gallbladder, were detected in 32% of the infected individuals. Clinical symptoms and ultrasonographic changes were common in subjects 21-40 years of age and older. Satisfactory resolution of morbidity was observed during two years follow-up on days 0, 60, 180, 360, and 720, as shown by significant clinical improvement, normalization of laboratory parameters, and downgrading of ultrasonographic abnormalities. Portable ultrasonography has proved to be a reliable noninvasive technique in the evaluation of the morbidity due to opisthorchiasis in rural areas.

Artemether or artesunate followed by mefloquine as a possible treatment for multidrug resistant falciparum malaria

Plasmodium falciparum in south-east Asia is highly resistant to chloroquine and sulfadoxine-pyrimethamine. Mefloquine used to be the chemosuppressant drug of choice in areas with chloroquine resistance. However, sensitivity to this drug has recently decreased in Thailand, Cambodia and Myanmar, and there is no suitable single alternative drug. We therefore investigated possible alternative combination therapies for multidrug resistant falciparum malaria. 120 male Thai patients at Makarm Malaria Clinic, Chantaburi, in eastern Thailand were allocated at random to receive either oral artemether (group A) or artesunate (group B) at a single dose of 300 mg on day 1, both followed by mefloquine, 750 and 500 mg at 24 and 30 h, respectively. Follow-up was on days 1, 2, 7, 14, 21, 28, 35 and 42. Patients in both groups had a rapid initial response to treatment; in most cases parasitaemia was cleared within 24 h, and fever was cleared within 24 h in 62% and 76.7% of the patients in groups A and B, respectively. 58 patients in group A and 57 in group B completed follow-up and cure rates were 98% and 97%, respectively. Reinfection could not be excluded for the 3 patients with recrudescences; all were cured with a repeated course of treatment. No serious adverse effect was observed in either group, only mild and transient nausea, vomiting and loss of appetite, with no significant difference between the 2 groups. These results suggest that a single oral dose of 300 mg of either artemether or artesunate followed by 1250 mg of mefloquine in 2 divided doses is effective against multiple drug resistant falciparum malaria. Either regimen can be considered as a suitable 'stand-by' in endemic areas of multiple drug resistant falciparum malaria.

Plasma quinine concentrations in falciparum malaria with acute renal failure

Plasma quinine (Qn) monitoring was performed in 32 patients with severe falciparum malaria (10 with acute renal failure (ARF) and 22 with other severe manifestations) who were treated with the standard regimen of 10 mg/kg body weight Qn dihydrochloride, with a loading dose of 20 mg/kg body weight. Median plasma Qn concentrations prior to the first dose on each day were approximately 10-30% higher in ARF patients than in non-ARF patients during acute infection. Seven patients underwent haemodialysis; 2 died after 2 cycles. There were no significant changes in plasma Qn concentrations in patients with ARF during haemodialysis. No Qn was detectable in haemodialysate fluids. This suggests that dosage adjustment of Qn during haemodialysis is unnecessary. Cardiotoxity of Qn must be of concern in malaria patients with ARF after 3 days of Qn therapy, and ECG monitoring during Qn infusion is recommended in all severe malaria patients with persistent ARF. If there is any arrhythmia, the infusion should be discontinued. However, in some hospitals where ECG facilities are not available, reduction in Qn dosage in persistent ARF patients should be considered after the third day of therapy. The appropriate dosage reduction should be further studied. Monitoring of total plasma Qn concentrations (which has been used routinely) is of no value for predicting the cardiotoxicity in ARF patients; monitoring of free Qn would be more appropriate. However, ECG seems to be the practical procedure to monitor cardiotoxicity of Qn. It may be possible to use the QTc interval to estimate the Qn concentration in severe malaria patients without ARF, but not in patients with persistent ARF.

Quinine-tetracycline for multidrug resistant falciparum malaria

Plasmodium falciparum in Southeast Asia is highly resistant to chloroquine and sulfadoxine/ pyrimethamine. Quinine-tetracycline has been used as a second line treatment for uncomplicated falciparum malaria, but duration of treatment varies from place to place. The 7-days course of this combination has been shown to be very effective. However, due to the cinchonism adverse effects, the patient compliance has not been satisfactory. We have evaluated the efficacy of a 7-days course of tetracycline in combination with either 5 or 7-days course of quinine. Ninety male Thai patients who were admitted to the Bangkok Hospital for Tropical Diseases were randomized to receive tetracycline 250 mg qid for 7 days in combination with either quinine 600 mg tid for 5 days (Q5T7; group A) or quinine 600 mg tid for 7 days (Q7T7; group B). The patients were hospitalized for 28 days. Patients in both groups had a comparable initial response to treatment, with the clearance of fever and parasites within 4 days. There were 46 and 40 patients in group A and B, respectively, who completed the 28 day of follow-up. The cure rates were 87 and 100%, respectively for group A and B. No serious adverse effects were found in either group; transient nausea, vomiting and tinnitus were common findings. The incidence of adverse effects was not different between the two groups. The results from the present study suggest that a short course treatment of quinine (Q5T7) had significantly decreased the cure rate. In areas with quinine resistant falciparum malaria, a full course of 7-days quinine, in combination with 7-days course of tetracycline is recommended for hospital treatment. However, an alternative shorter course of antimalarials is suggested for home treatment.

Comparison of artemether and quinine in the treatment of severe falciparum malaria in south-east Thailand

One hundred and two Thai patients with severe falciparum malaria (92 males and 10 females) were allocated at random to receive either the standard regimen of quinine infusion (52 cases) or intramuscular artemether (50 cases). The patients in both groups had comparable admission clinical and laboratory data. Artemether gave a better survival rate (87.2% vs. 63.3%) and parasite clearance time (54 vs. 78 h) than quinine. Fever clearance times (79 h vs. 84 h) and time to recovery of consciousness (48 h in both groups) were comparable. Previous treatment with quinine or mefloquine had no influence on treatment outcome. The most common adverse effect in patients treated with quinine was tinnitus. Two patients had severe hearing impairment which resolved within 1 week after the end of treatment. Mild, transient pain was noted at the injection site of artemether but no abscess formed. QTc wave prolongation was seen in most patients receiving quinine; however, no arrhythmia was observed despite the high concentration of quinine in some patients who had received quinine before admission. Complications developed in 7 survivors in each treatment group. No patient in the artemether group had neurological sequelae after recovery of consciousness, but 2 in the quinine group had left facial palsy and one had a myasthenia gravis-like syndrome. No patient died with complications in he artemether group, but 7 died with pulmonary complications in the quinine group.

Serum antibody responses in opisthorchiasis

We evaluated an enzyme-linked immunosorbent assay using crude parasite homogenates as a diagnostic test for Opisthorchis viverrini infection in humans. Serum antibody (Ab) responses to O. viverrini adult worm homogenate (AWH) and metacercaria homogenate (MH) were studied in 83 infected residents of an opisthorchiasis-endemic area in Thailand. Elevated levels of Ab persisted for over 1 year following curative treatment with praziquantel, and cross-reactivity to O. viverrini AWH and MH antigens was observed in sera from individuals with other parasitic infections. Serum Ab to crude AWH and MH are therefore unsuitable for immunodiagnosis since they may be non-specific and would not differentiate between ongoing and past infection.

Artemether-mefloquine combination in multidrug resistant falciparum malaria

Plasmodium falciparum in Thailand is highly resistant to chloroquine and sulfadoxine/pyrimethamine and there is increasing resistance to the alternative antimalarials, quinine and mefloquine. In eastern Thailand, the cure rates of mefloquine at 750 and 1250 mg were 30% and 55%, respectively. The use of drug combinations may be necessary in areas where drug-resistant parasites exist. 159 male Thai patients in Chantaburi, eastern Thailand, were allocated at random to receive either oral artemether at a single dose of 300 mg on the first day followed by mefloquine 750 mg at 24 h and 500 mg at 30 h (group A), or oral artemether at a single dose of 300 mg on the first day, mefloquine 750 mg at 24 h and placebo at 30 h (group B). The follow-up was on days 1, 2, 7, 14, 21, 28, 35 and 42. Most patients in both groups had a rapid initial response to treatment, parasitaemia being cleared within 24 h and fever cleared within 48 h in both groups. The cure rates were 97% and 90%, respectively, for groups A and B. No serious adverse effect was seen in either group; mild and transient nausea, vomiting and loss of appetite were noted. The adverse effects did not differ between the 2 groups. The results suggested that a single oral dose of artemether (300 mg) can markedly improve the cure rate of mefloquine at a dose of 750 or 1250 mg in multiple drug-resistant falciparum malaria.

Integration of control measures for malaria vectors in endemic areas of Thailand

Various vector control measures were applied in different endemic areas in two provinces, Saraburi and Chanthaburi, with comparison among different control measures. Application of IGR (insect growth regurator, pyriproxyfen) was introduced at Wat Tam Pra Pothisat, Tab-Kwang District, Saraburi Province. Some integration measures were performed at villages 6 and 8, Patavee, Makham District, Chanthaburi Province. In Tab-Kwang District with low malaria endemicity at the study site predators were not able to be released due to rapid velocity of running water. IGR could effectively control malaria compared to the basin released predators. Another endemic areas villagers 6 and 8, Patavee, Makham, Chanthaburi Province was chosen. Highly endemic multidrug resistant malaria has been prevalent for many years in this area. Integration of Kanda's trapping system, application of IGR, use of both residual spraying and impregnated bed-net methods with etofenprox successfully interrupted malaria infection. The application of these methods as an integrated control system could be adjusted to environmental conditions. The results of this study suggest rapid effective vector control.

Opisthorchis viverrini infection in Thailand: symptoms and signs of infection--a population-based study

A population-based study of the clinical, laboratory and ultrasonographic findings in patients suffering from mild or moderate opisthorchiasis in Prachinburi province, Thailand was conducted in 1990-1992. The effectiveness of treatment with praziquantel at 40 mg/kg body weight was evaluated. After treatment, a long-lasting, marked improvement in the well-being of the study group was observed. Symptoms common in opisthorchiasis infection decreased in intensity and the clinical response showed total or partial remission in 98% of all cases studied. Total and direct bilirubin concentrations decreased significantly and remained low up to the end of the follow-up period of 2 years, indicating a reduction in cholestasis. Also, white blood cell counts decreased initially, which can be interpreted as a reduction in inflammation intensity. No relationship was found between intensity of infection and age or clinical findings. Population-based treatment of opisthorchiasis appears to have had a significant impact on public health in north-east Thailand. However, it is also evident that drug therapy alone will not solve the opisthorchiasis problem, as indicated by the reinfection rate of almost 10% at the end of the study.

Serum antibody response to Opisthorchis viverrini antigen as a marker for opisthorchiasis-associated cholangiocarcinoma

The liver flukes Opisthorchis viverrini and Clonorchis sinensis chronically infect over 30 million people in south-eastern Asia, resulting in significant morbidity and a predisposition to cholangiocarcinoma (CCA). Liver fluke-associated CCA carries a poor prognosis, partly because it is often detected at a late and advanced stage. The development of improved diagnostic methods, particularly for early CCA, may improve chances of survival and cure. Accordingly, we explored the use of immunological responses to liver fluke antigens as a potential means of identifying individuals at high risk for liver fluke-associated CCA. Serum antibody responses to O. viverrini adult worm homogenate and metacercaria homogenate (MH) were studied using enzyme-linked immunosorbent and immunoblot assays in 65 infected residents of an opisthorchiasis-endemic area in Thailand. Antibody levels correlated with liver ultrasonography (U/S) findings, and immunoblot analysis revealed a 91/93 kDa MH doublet recognized only by sera of individuals with severe liver U/S findings, including CCA. These results suggest that serum antibody responses to liver fluke antigens may be useful in the identification of infected individuals who are at high risk for liver fluke-associated CCA.

Possible protective immunity in human opisthorchiasis

Chronic infections with the liver flukes Opisthorchis viverrini and Clonorchis sinensis affect over 30 million people in southeastern Asia. With ongoing exposure, reinfection readily occurs following curative treatment and cumulative infections result in significant morbidity and a predisposition to cholangiocarcinoma. Though protective immunity has never been described in human opisthorchiasis, heterogeneity in worm burden occurs and a small number of exposed residents of endemic areas remain apparently uninfected. To explore the nature of this heterogeneity, we compared levels of serum antibody (Ab) to O. viverrini measured by an enzyme-linked immunosorbent assay in 83 stool egg-positive and 49 stool egg-negative residents of an O. viverrini-endemic area in Thailand. Compared to the egg-positive residents, the egg-negative group had significantly higher levels of immunoglobulin (Ig)G, IgA and IgM to adult worm homogenate (AWH) and total Ab to metacercaria homogenate (MH). Furthermore, immunoblot analyses revealed that a significantly higher proportion of sera from the egg-negative residents had IgA reactivity against a 38-kDa AWH antigen and IgM reactivity against carbohydrate epitopes of a 42-kDa AWH glycoprotein antigen. These findings support a hypothesis that the egg-negative group includes individuals who may be immunologically resistant to this usually chronic infection.

Mefloquine pharmacokinetics in pregnant women with acute falciparum malaria

Mefloquine has an established place in the treatment of chloroquine-resistant falciparum malaria. To investigate mefloquine pharmacokinetics in pregnancy, 9 untreated pregnant women aged 16-33 years and 8 non-pregnant females aged 16-38 years received an average of 15 (range 13-19) mg mefloquine/kg body-weight as single-dose treatment for uncomplicated falciparum malaria. Regular blood samples were taken during the subsequent 48 h and then intermittently for 3-26 d after treatment. Whole blood mefloquine concentrations were analysed by high-performance liquid chromatography and a one-compartment open pharmacokinetic model was fitted to the data. Peak mefloquine concentrations were significantly lower in the pregnant patients (median [range]; 1257 [650-1584] vs. 1617 [1051-3111] ng/mL) and the total apparent volume of distribution (Vd/f) was larger (10.8 [8.3-26.1] vs. 10.0 [4.8-13.9] L/kg; P < 0.05 in each case), consistent with an expanded circulating blood volume and increased tissue binding in pregnancy. There was no significant difference between the 2 groups in half-times of absorption or elimination (P > 0.1), and systemic clearance rates were also similar. These results suggest that pregnant patients need larger doses of mefloquine than non-pregnant women to achieve comparable blood levels, an important consideration in areas where multi-drug resistant falciparum malaria is emerging.

High dose of primaquine in primaquine resistant vivax malaria

The efficacy of low dose chloroquine, characteristic pattern of relapse and the relapse rate in vivax malaria after high dose primaquine were investigated in 167 Thai patients. 87 patients were allocated at random to receive 300 mg, and 80 received 450 mg of chloroquine on the first day of admission. All patients in both groups showed a rapid response with comparable fever clearance times (27.3 vs. 26.1 h) and parasite clearance times (67.1 vs. 58.1 h). After recovery and clearance of parasitaemia, the patients were allocated at random (double blind) to receive 2 dosage regimens of primaquine, a daily dose of 15 mg or 22.5 mg for 14 d. Relapses in both groups occurred within 6 months; no patient relapsed beyond that period. The relapse rate in the primaquine 15 mg group was significantly higher than that in the 22.5 mg group (17.5% vs. 2.4%).

Mefloquine prophylaxis prevents malaria during pregnancy: a double-blind, placebo-controlled study

A double-blind, placebo-controlled study of mefloquine antimalarial prophylaxis in pregnancy (> 20 weeks of gestation) was conducted in 339 Karen women living in an area of multidrug-resistant malaria transmission on the Thai-Burmese border. Mefloquine gave > or = 86% (95% confidence interval [CI], 59%-94%) protection against Plasmodium falciparum and complete protection against Plasmodium vivax infections. Mefloquine prophylaxis was well tolerated; use of an initial loading dose (10 mg/kg) was associated with transient dizziness, but there were no other significant adverse effects on the mother, the pregnancy, or infant survival or development (followed for 2 years). Falciparum malaria was associated with maternal anemia and a mean reduction in birth weight in gravidae I, II, and III of 225 g (95% CI, 26-423). Maternal anemia at delivery (hematocrit < 30%) was associated with increased infant mortality: 26% versus 15% (relative risk, 1.9; 95% CI, 1.1-3.2). Mefloquine is safe and effective for antimalarial prophylaxis in the second half of pregnancy.

Comparison of oral artesunate and quinine plus tetracycline in acute uncomplicated falciparum malaria

In Thailand Plasmodium falciparum malaria is highly resistant to available antimalarials. Investigations on the efficacy of existing antimalarials and of alternative drugs are urgently needed. Artesunate has been shown to be effective against falciparum malaria, but is associated with a high recrudescence rate. We have carried out a comparative clinical trial of the standard regimen of quinine + tetracycline versus oral artesunate at a 700-mg total dose given over 5 days to patients with acute uncomplicated falciparum malaria. The 64 male patients who took part in the study were randomized to receive either quinine-tetracycline (33 patients) or oral artesunate (31 patients). All the patients were admitted to the Bangkok Hospital for Tropical Diseases for 28 days. Oral artesunate had faster parasite and fever clearance times than the combination quinine-tetracycline, but the cure rate was not significantly different for the two regimens. However, the occurrence of adverse effects, such as tinnitus, was significantly higher in the quinine-tetracycline group. Surprisingly nausea and dizziness were rather common with artesunate. The possibility of neurological adverse effects for artesunate should also be borne in mind. Oral artesunate (700 mg given over 5 days) is effective and better tolerated than the combination quinine-tetracycline. The cure rate we obtained is higher than that reported in previous studies with 600 mg of oral artesunate given over 5 days. Oral artesunate can be considered as an alternative drug for multiple-drug-resistant falciparum malaria; however, adverse effects, particularly neurotoxicity, should be closely monitored before its widespread use can be recommended.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics of mefloquine alone or in combination with artesunate

A randomized comparative trial of the pharmacokinetics and pharmacodynamics of oral doses of mefloquine and of mefloquine in combination with artesunate was carried out on 20 Thai male patients with acute, uncomplicated falciparum malaria. The patients were randomized to receive either mefloquine alone (8 patients; 1250 mg of mefloquine--initial dose, 750 mg; followed 6 hours later by 500 mg), or in combination with oral artesunate (12 patients--initial dose, 200 mg of artesunate; followed by 750 mg and 500 mg of mefloquine 6 hours and 12 hours later, respectively). The patients who received mefloquine alone all showed initially good responses to the treatment, with mean +/- SD values for the fever clearance time (FCT) and parasite clearance time (PCT) of 44.7 +/- 43.1 hours and 82.3 +/- 52.3 hours, respectively. Two patients had recrudescences on day 20 and day 31 (RI response). The cure rate was 75%, and one patient had Plasmodium vivax in his peripheral blood on day 52. The patients who received the combination treatment were clinically markedly improved, with a relatively shorter FCT (31.2 +/- 12.4 hours) and significantly shorter PCT (47.5 +/- 19.6 hours). Four had recrudescences on days 12, 18, 26 and 33; the cure rate was 66%. Artesunate caused three significant changes in mefloquine pharmacokinetics: a decrease in the maximum concentration (Cmax: 1623 ng.ml-1 versus 2212 ng.ml-1); an increase in the clearance rate (Cl/f:2.9 ml.min-1.kg-1 versus 1.1 ml.min-1.kg-1); and an expansion of the volume of distribution (Vdz/f: 31.8 l.kg-1 versus 25.0 l.kg-1).

Pharmacokinetics of praziquantel in patients with opisthorchiasis

The pharmacokinetics of praziquantel was investigated in 9 Thai male patients with asymptomatic opisthorchiasis (stool positive) and 9 patients (6 males, 3 females) with moderately advanced infection (hepatomegaly). The geometric means of the pretreatment Opisthorchis viverrini egg count in these patients were 2,950 vs 4,468 eggs per gram of stool. The results indicate the impairment of metabolism of praziquantel in the moderately advanced stage opisthorchiasis. The pharmacokinetics of the drug in these patients during the acute infection was markedly altered when compared with that after recovery and in patients with early stage of the infection. The clearance rate (Cl/f) was significantly reduced [medians and ranges of 106 (43-242) vs 192 (112-692) and 171 (133-427) ml/min/kg] and the t1/2z and MRT were prolonged [t1/2z: 3.8 (2.0-6.2) vs 2.7 (1.7-4.3) and 2.3 (1.7-2.8) hours; MRT: 6.2 (3.2-11.0) vs 4.6 (2.7-6.2) and 4.5 (2.9-5.1) hours]. In addition, AUCo-alpha was significantly greater [6.0 (2.5-15.6) vs 3.5 (0.6-6.0) and 3.9 (1.6-5.0) micrograms hour/ml].

Mefloquine level monitoring in patients with multidrug resistant Plasmodium falciparum on the Thai Myanmar border

A total of 42 patients with uncomplicated falciparum malaria who attended the malaria clinic in Mae Sot, Tak Province were treated with single oral dose of MSP 3 tablets (Fansimef, equivalent to 750 mg of mefloquine) concurrently with primaquine (30 mg). They all contracted the infection from Cambodia. The aim of the study was to monitor the efficacy of MSP 3 tablets for the treatment of this highly multiple drug resistant strains of Plasmodium falciparum in this area. Of the 39 patients included for efficacy assessment, 13 (33.3%) patients had sensitive responses, whereas 15 (38.5%) and 8 (20.5%) had RI and RII types of response, respectively. Melfoquine concentrations on Day-3 after treatment in patients with sensitive and treatment failure groups were comparable; the respective mean (SD) values were 665 (279) and 772 (264) ng/ml.

Mefloquine monitoring in acute uncomplicated malaria treated with Fansimef and Lariam

Mefloquine levels were compared between Plasmodium falciparum malaria patients with sensitive response and those with treatment failure who received 3 drug regimens of mefloquine (46 patients with MSP 3 tablets (Fansimef), 38 and 34 with mefloquine (Lariam) 750 mg and 1,250 mg). Mefloquine concentrations on Day-1 in any regimens in patients with treatment failure were significantly lower than those from the sensitive response, whereas there was no difference in the concentrations on Day-7. However, MIC values of mefloquine prior to drug treatment were comparable in both groups. The study suggests that pre-treatment in vitro sensitivity testing was a non-reliable indicator of clinical outcome. Mefloquine concentration on the first day after treatment is a better predictor of the treatment outcome.

Mefloquine levels in patients with mefloquine resistant Plasmodium falciparum in the eastern part of Thailand

A total of 99 patients with uncomplicated falciparum malaria who attended the malaria clinic in Bo Rai, Trat Province were treated with a single oral dose of MSP 3 tablets (Fansimef; equivalent to 750 mg of mefloquine) concurrently with primaquine (30 mg). The aim of the study was to detect RII and RIII types of response with 3 tablets of MSP. Seven (8.1%) and 22 patients (25.3%) had RII and RIII types of response, respectively, and 58 (66.8%) had no parasitemia on Day-7 (S or RI response). Mefloquine concentrations on Day-3 after treatment in patients in the S/RI group were significantly higher than those with early treatment failure (RII, RIII), with the respective mean (SD) values of 1,959 (696) and 1,622 (863) ng/ml. The mean concentrations of mefloquine in these patients with RII and RIII types of response were higher than those with a sensitive response in a previous study. The result suggests that Plasmodium falciparum strains in this part of the country are highly resistant to mefloquine and that blood levels of mefloquine on Day-3 may also be a good indicator of treatment outcome in this particular area.

Intramuscular artemether in female patients with uncomplicated falciparum malaria

Thirty-three female patients suffering from acute uncomplicated falciparum malaria were treated with intramuscular artemether for 5 days during May-October 1990. Fourteen patients received 160 mg as an initial dose, followed by 80 mg daily for 4 days. Nineteen patients with low body weight (mean weight of 36.5 kg) were given artemether at 3.2/kg as a loading dose and followed by 1.6 mg/kg/dose for another 4 days. The geometric mean of parasitemia was 17,378/microliters (range 640-234,720). The mean fever (FCT) and parasite clearance time (PCT) were 41.8 and 49.4 hours, respectively. Two patients had probable intercurrent infection with FCT of over 7 days. Thirty-one patients had completed the 28-day follow-up. The cure rate was 90.3% (28/31). Three patients had RI type of response. Mild and transient adverse effects were experienced in eleven patients; these consisted of pain at the injection sites, vomiting, dizziness, abdominal pain, palpitation and diarrhea. These symptoms may in part be due to symptom complex of malaria. The MIC of chloroquine, quinine, quinidine and mefloquine was performed in all patients but only 25 isolates were successfully cultured and tested. The MIC of all tested drugs were shown to be higher than that of previous studies, suggesting that there is a rapid increase of mefloquine resistant strains of falciparum malaria. In conclusion, artemether proves to be effective against multiple drug resistant falciparum malaria (including mefloquine resistant strains) and can be considered as an alternative antimalarial to mefloquine. The drug was well tolerated in female patients with mild and transient side-effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical trials with halofantrine in acute uncomplicated falciparum malaria in Thailand

The antimalarial efficacy of halofantrine was compared with mefloquine in an open-label, randomized comparative trial in adult male patients with acute uncomplicated falciparum malaria. Twenty-eight patients received halofantrine and 27 received mefloquine. Halofantrine was administered in 3 doses of 500 mg at 6 hour intervals and mefloquine was administered in divided doses of 1,250 mg or 1,500 mg depending on whether the patients weighed less than or more than 60 kg. The patients were followed for 42 days and observed for drug tolerance and evidence of recrudescence. Response to treatment was favorable with both drugs, but three patients (two treated with halofantrine and one with mefloquine) did not completely eliminate malaria parasites from peripheral blood films in seven days. The parasite and fever clearance times were 75.6 and 55.7 hours, and 80.1 and 61.3 hours, respectively for halofantrine and mefloquine. However, 12 patients recrudesced during the 42 day follow-up period. Nine of these had been treated with halofantrine and three with mefloquine. The 42-day cure rate for the two drugs was 56% and 84%, respectively. The side-effects of halofantrine and mefloquine were comparable and transient. These are diarrhea, dizziness, orthostatic hypotension and black out. However, vomiting was found to be more common in mefloquine group (41% vs 22%).

A comparison of the pharmacokinetic and pharmacodynamic properties of quinine and quinidine in healthy Thai males

1. Eight healthy Thai males, aged 19-27 years, received quinine or quinidine dihydrochloride 10 mg kg-1 body weight by intravenous infusion over 1 h. At least 1 week later, the alternative alkaloid was administered. 2. The terminal elimination half-time of quinidine was shorter than that of quinine (median [range]; 5.7 [5.0-10.0] vs 9.9 [8.8-15.1] h, P < 0.01), the volume of distribution at steady state (Vss) for quinidine was larger than that for quinine (3.5 [2.5-5.6] vs 3.1 [1.8-4.1] 1 kg-1; P = 0.02) and quinidine was less bound to plasma proteins (% free drug: 22.8 [15.4-47.2] vs 9.4 [7.3-15.0]%, P < 0.01). Total clearance was greater for quinidine (7.7 [3.9-11.4] vs 3.4 [1.8-4.6] ml min-1 kg-1, P < 0.01) but not for clearance of unbound drug (32.2 [14.6-50.4] vs 29.9 [20.2-50.9] ml min-1 kg-1 respectively, P > 0.2). 3. Side-effects, including transient hypotension after quinidine in two cases, were mild. 4. Both drugs produced prolongation of the rate-corrected QT interval (QTc), with similar rates of elimination from the cardiac conduction 'effect' compartment (keo; 4.14 [0.03-15.33] h-1 for quinine, 3.74 [1.63-13.14] h-1 for quinidine, P > 0.19). Using a linear concentration-response model, the intercept ('threshold') for quinidine effect was lower than that for quinine (P = 0.004) but the slopes (change in QTc for a given change in free drug concentration) were similar (P = 0.56).(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics of quinine, quinidine and Cinchonine when given as combination

Pharmacokinetics of quinine, quinidine and cinchonine when given as a combination were evaluated in Thai patients with falciparum malaria during acute infection and convalescence. The combination of quinine, quinidine and cinchonine was randomly given to thirteen patients at 400 mg or 600 mg (consisting of one-third of each component; 7 patients were enrolled in 400 mg regimen and 6 in 600 mg regimen) intravenously every 8 hours for 7 days. The drug combination was given again at day 35 to define the pharmacokinetics of each drug during convalescence. All patients with the 600 mg regimen had good response with 100% cure rate while patients with the 400 mg regimen had a good initial response but one patient recrudesed on day 46. This particular patient had plasma concentrations of all three drugs lower than the mean values of patients with sensitive responses. The plasma levels of quinine and quinidine obtained from the present study were higher than that expected from one-third of the conventional dose (600 mg) when given alone, suggesting drug combination interaction. The terminal half-lives of each of the three components were prolonged during acute malaria when compared to those obtained during convalescence.

Two-site sandwich ELISA for detection of Plasmodium vivax blood stage antigens using monoclonal and polyclonal antibodies

Two systems of sandwich enzyme-linked immunosorbent assay (ELISA), a two-site monoclonal antibody sandwich ELISA MAb-MAb sandwich ELISA) and a two site polyclonal-monoclonal antibody sandwich ELISA (PAb-MAb sandwich ELISA) for the detection of Plasmodium vivax antigens were developed. The assays showed good correlation with the level of parasitemia when tested against serially diluted P. vivax parasites (r = 0.937, and 0.997 for MAb-MAb and PAb-MAb sandwich ELISA, respectively), with the ability to detect as few as 6.68 parasites/10(6) erythrocytes and 2.69 parasites/10(3) erythrocytes, respectively. The MAb-MAb sandwich ELISA was specific, since it was positive only with P. vivax-infected erythrocytes from vivax malaria patients and negative when erythrocytes from 34 healthy individuals and 30 falciparum malaria cases were tested. In contrast, cross-reaction was found in the PAb-MAb sandwich ELISA when the plates were coated with polyclonal IgG and tested against the serially diluted P. falciparum SO strain antigen prepared from in vitro cultures. Comparison between the two systems of two-site sandwich ELISA showed that the MAb-MAb sandwich ELISA was superior to the PAb-MAb sandwich ELISA: (1) it gave a higher sensitivity when tested with serially diluted P. vivax antigen preparations from vivax malaria patients; (2) it gave a higher specificity when tested with the SO strain of P. falciparum from in vitro cultures, (3) it gave a lower absorbance value when tested with erythrocytes from healthy individuals. All 281 cases of vivax malaria already proven by microscopic examination were positive by MAb-MAb sandwich ELISA.(ABSTRACT TRUNCATED AT 250 WORDS)

Artemether in the treatment of multiple drug resistant falciparum malaria

Artemether has the potential to be an alternative antimalarial for multiple drug resistant falciparum malaria. However, it has been associated with high recrudescent rates which may be due to incorrect dosage regimens. The dosage regimens are varied from country to contry. We have carried out a comparative study of two dosage regimens, ie 480 mg and 600 mg total dose given over 5 days in uncomplicated and severe falciparum malaria. 167 patients were included in the study, 61 with acute uncomplicated falciparum malaria and 106 with severe malaria. All patients showed a good initial response. The difference in total dose had no effect on the parasite or fever clearance time (PCT or FCT). However, the severity of the disease did have some influence of these times. The PCT and FCT from either regimen of uncomplicated malaria were significantly faster than those of severe malaria (p < 0.005 and = 0.05, respectively). The cure rate seems to have some correlation with the amount of drug given and severity of the disease. The cure rates in uncomplicated malaria were 84 and 92%, respectively, for 480 mg and 600 mg. In severe malaria the cure rates dropped to 65 and 76%, respectively, for 480 and 600 mg. We conclude that artemether can be considered as an alternative antimalarial for multiple drug resistant falciparum malaria. However, the cure rate of severe falciparum malaria in this study is not considered satisfactory in areas with multiple drug resistant falciparum malaria. Further studies are needed to assess the curative efficacy with different dosage regimens.(ABSTRACT TRUNCATED AT 250 WORDS)

Preliminary report: a comparative clinical trial of artemether and quinine in severe falciparum malaria

Twenty-six patients with severe falciparum malaria were randomized to be treated with quinine or artemether. Twelve patients received quinine at the standard dose and fourteen patients received artemether intramuscularly at a total dose of 640 mg over 7 days. The patients were kept in the hospital for at least 7 days. Peripheral smear was performed 6-hourly until there was no parasitemia, then daily until discharged. Adverse effects were monitored through physical examination, laboratory findings and questionnaires. Laboratory examination was performed on admission, day 2, day 4 weekly until discharged. The patients in both groups were comparable in age, body weight, admission parasitemia, hemoglobin and white blood cell count. The survival rates were 93% and 58% in artemether and quinine groups, respectively (p = 0.052 at 95% confidence, using Fisher's exact test). The parasite and fever clearance times, and the time taken to gain consciousness in cerebral malaria patients were not significantly different between the two groups. Adverse effects in the quinine group consisted of dizziness and vertigo which were found in 4 patients. No adverse effects were noticed in the artemether group. This preliminary report suggests that artemether is a good alternative drug for severe falciparum malaria and seems to be better than quinine regarding survival rate and side effects. Confirmation of these findings in a larger study size is needed.

Fansimef for prophylaxis of malaria: a double-blind randomized placebo controlled trial

At a time when Fansimef, the fixed combination of mefloquine, sulfadoxine and pyrimethamine was considered for prophylaxis of falciparum malaria, a randomized double-blind study comparing the efficacy and tolerability of Fansimef with that of Lariam (mefloquine), Fansidar, chloroquine and placebo in malaria prophylaxis was performed in Thailand from July 1987 to January 1988. The study population of 602 adult males was recruited in Pak Tongchai District, some 360 km North-East of Bangkok, where multiresistant P. falciparum is endemic. All active treatments and placebo were given once weekly for 24 weeks with doses as follows: Fansimef: 125 mg mefloquine + 250 mg sulfadoxine + 12.5 mg pyrimethamine (1 half-strength tablet); Lariam: 125 mg mefloquine (1 half-strength tablet); Fansidar: 500 mg sulfadoxine + 25 mg pyrimethamine; chloroquine; 300 mg. A loading dose of 2 half-strength tablets was given in the Fansimef group in weeks 1 and 2 and in the Lariam group in weeks 1 to 4. The incidence of acute episodes of P. falciparum per 100 person months of prophylaxis was 0.17 each in the Fansimef and the Lariam groups, 1.18 in the Fansidar group, 0.69 in the chloroquine group and 0.64 in the placebo group (differences statistically not significant). Clinically adverse events were reported by 170 subjects (Fansimef 28, Lariam 29, Fansidar 41, choroquine 43, placebo 29; differences statistically not significant). The most frequent adverse events in all groups were headache, sleepiness, dizziness and weakness.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of oral artemether and mefloquine in acute uncomplicated falciparum malaria

Plasmodium falciparum malaria in Thailand is highly resistant to available antimalarials, and alternative drugs are needed urgently. Artemether is effective against falciparum malaria but associated with a high recrudescence rate. The proper dosage regimen remains to be defined. We have done a clinical trial comparing mefloquine 1250 mg in divided doses with oral artemether at 700 mg total dose given over 5 days in acute uncomplicated falciparum malaria. 46 patients, admitted to the Bangkok Hospital for Tropical Diseases, were randomised to receive either mefloquine (12) or artemether (34). Hospital follow-up was 28 days for the artemether group and 42 days for the mefloquine group. Oral artemether gave a significantly faster parasite clearance time than mefloquine (30 vs 64 h), and a significantly better cure rate (97 vs 64%) with fewer episodes of dizziness and vomiting. Oral artemether at 700 mg given over 5 days is effective and well tolerated. The cure rate with this regimen is higher than that reported by previous studies with 600 mg intramuscular artemether given over 5 days. Oral artemether can be considered as an alternative drug for multiple-drug-resistant falciparum malaria.

Effect of tetracycline on mefloquine pharmacokinetics in Thai males

The kinetics of a single oral dose of mefloquine given either alone or with tetracycline has been studied in 20 healthy Thai male volunteers. There was a significantly higher maximum whole blood mefloquine concentration after coadministration with tetracycline (1600 vs 1160 ng.ml-1), as well as a significantly reduced terminal half-life (14.4 vs 19.3 days), mean residence time (11.9 vs 16.0 days) and volume of distribution at steady state (13.3 vs 19.9 1.kg-1). Although there was no significant change in the AUC from zero time to infinity, the AUC from zero time to 7 days was significantly increased by tetracycline (6.18 vs 4.76 micrograms.ml-1.day). The changes in mefloquine disposition after tetracycline treatment are probably due to a reduction in enterohepatic recycling. The initial increase in mefloquine AUC without an apparent increase in side-effects suggests that this combination may have a place in the treatment of multi-drug resistant falciparum malaria.

Polymorphonuclear leucocyte elastase in Plasmodium falciparum malaria

Sixty-one patients with falciparum malaria were studied prospectively to determine the plasma concentrations of the lysosomal proteinase, polymorphonuclear leucocyte elastase (PMN-elastase) and their relationship to disease severity. The patients were divided into 3 groups; severe (parasitaemia > 5%) or vital organ dysfunction (n = 23), moderate (parasitaemia 1%-5% without complications) (n = 15), and mild (parasitaemia < 1%) (n = 23). The mean plasma PMN-elastase level in 10 healthy Thai volunteers was 49.5 (SD = 21.6) ng/ml (range 33-65 ng/ml). Plasma PMN-elastase concentrations on admission were elevated (> 2 x SD above normal) in all patients with severe malaria and were above 100 ng/ml in 86.6% and 65% of the moderately severe and mild patients respectively. PMN-elastase levels during the first 3 hospital days were significantly higher in severe malaria compared with the other 2 groups (P = < 0.001-0.013). The levels decreased as the patients became afebrile and aparasitaemic. Admission plasma concentrations of PMN-elastase correlated directly with bilirubin (rs = 0.50, P < 0.001), serum glutamic oxalacetic transaminase (rs = 0.54, P0.001), parasite count (rs = 0.62, P < 0.001), blood urea nitrogen (rs = 0.54, P < 0.001) and inversely with antithrombin III activity (rs = 0.54, P < 0.001) and the platelet count (rs = 0.58, P < 0.001). Polymorphonuclear leucocyte activation may contribute to the pathogenesis of severe malaria.

Clinical trials of mefloquine with tetracycline

A comparative trial of the combination of mefloquine or MSP with tetracycline was carried out in fifty-one adult Thai male patients with acute falciparum malaria. The patients were randomized to receive either the combination of tetracycline (250 mg qid for 7 days) with mefloquine 4 tablets (1,000 mg) or with MSP 4 tablets (one tablet contains 250 mg mefloquine, 500 mg sulfadoxine and 25 mg pyrimethamine). Fifty patients had a complete 28-day follow-up period. Both regimens produced similar efficacy with no difference in adverse effects. In the mefloquine plus tetracycline group, the cure rate was 72% (18/25). One patient had an RIII response, the others showed initial response to the treatment with FCT and PCT of 40.7 +/- 27.4 and 76.2 +/- 34.2 hours (mean +/- SD) respectively. However, 6 patients developed recrudescence between days 17 and 29 (RI), 3 of these had vomiting. In the MSP plus tetracycline group, the cure rate was 76% (19/25). The means (+/- SD) of FCT and PCT were 44.7 +/- 38.0 and 80.6 +/- 25.0 hours, respectively. Six patients had recrudescence between days 17 and 31 (RI), 2 of these had vomiting. Although the addition of tetracycline improved the cure rate of mefloquine when compared with standard dose of mefloquine alone (3 tablets), these combinations seem to be useful in areas where alternative drugs are not available.

Plasmodicidal effect of desferrioxamine B in human vivax or falciparum malaria from Thailand

Desferrioxamine B (DFO, Desferal), an iron chelator, was earlier shown to be active against Plasmodium falciparum in vitro and in vivo. The present open pilot study served to assess its clinical tolerability and efficacy in human malaria under hospital conditions. Continuous intravenous DFO was administered to 28 Thai males at a dose of 100 mg/kg over 24 h for 3 consecutive days. No other antimalarial therapy was administered unless recrudescence had occurred. The first 14 patients had symptomatic Plasmodium vivax (P.v.) malaria, while the other 14 patients were suffering from uncomplicated Plasmodium falciparum malaria (P.f.). Both groups were treated in Bangkok, where malaria transmission does not take place, and followed up, on the ward, for 3 weeks (P.v. group) or 4 weeks (P.f. group) after the start of therapy. In both groups DFO reduced the parasitaemia to zero within 106 and 57 h respectively. The fever clearance time was 55 and 60 h, respectively. The overall tolerability of DFO was good but 4 P.v. and 5 P.f. patients had transient visual blurring. Recrudescences were observed on average 15, respectively 10 days after the start of therapy. Only 2 P.v. patients and none of the P.f. patients remained free of recrudescences during the observation period. There was no apparent gametocytocidal effect of DFO on P.f.

Separation and characterization of adult worm proteins and glycoproteins from the liver fluke Opisthorchis viverrini

Detailed studies of liver fluke proteins and antigens are necessary to facilitate further investigation of the human immune responses to these parasites. Accordingly, Opisthorchis viverrini antigens were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. We initially encountered excessive background smearing, vertical streaking, and indistinct bands that were similar to problems previously described by investigators studying this and other trematodes including Schistosoma mansoni. These problems were especially evident with silver staining of proteins and occurred despite the extensive use of protease inhibitors. They were minimized by using mini (vs. large) SDS-PAGE and Coomassie blue protein staining. With the latter 2 techniques, adult worm somatic proteins and excretory-secretory products were separated and characterized. Immunoblots using rabbit anti-adult worm sera demonstrated that some of these proteins were antigens common to both the adult and metacercarial stages. Several of these antigens also corresponded (according to molecular weight) to glycoproteins, detected by concanavalin A blotting. These findings form a base for subsequent studies of the human immune response to liver fluke infection.

Thrombocytopenia in malaria

The relationship between platelet counts and platelet bound (direct) or platelet directed (indirect) serum antibody concentrations was studied in 17 patients with Plasmodium falciparum malaria and 12 patients with P. vivax malaria. Platelet counts rose with recovery from infection from 196 +/- 84 x 10(9)/l (mean +/- SD) and 195 +/- 34 x 10(9)/l to 319 +/- 99 and 283 +/- 62 x 10(9)/l respectively (p less than 0.002), but there was no relationship between either absolute platelet count or changes in counts and either indirect or direct platelet antibody levels. These findings suggest that a non-immunologically mediated mechanism is involved in the pathogenesis of thrombocytopenia in malaria.

Effect of mefloquine on electrocardiographic changes in uncomplicated falciparum malaria patients

Asymptomatic sinus bradycardia and sinus arrhythmia have been noted in malarial patients receiving mefloquine. The present study was designed to assess the effect of mefloquine on electrocardiogram in malarial patients. The study was carried out in 102 acute uncomplicated falciparum malarial patients who were treated with mefloquine 750 mg and 1,250 mg regimens and 18 healthy male volunteers receiving 750 mg of mefloquine. Electrocardiogram was performed at intervals after mefloquine administration for a period of 42 days. PR, QRS, QT, QTc, RR interval and cardiac arrhythmia were measured and read by EKG-analyser with confirmation by a cardiologist. Sinus bradycardia and sinus arrhythmia were found in 61.8% and 45.1%, respectively during the first week after treatment. The patients' heart rate decreased significantly on day 6 after mefloquine administration when compared to day 0. The occurrence of sinus bradycardia and sinus arrhythmia were significantly higher in malarial patients when compared with findings in healthy subjects of the same age group. It is unlikely that these changes are associated with mefloquine concentration as mefloquine peaks around 12-24 hours after administration. There were no significant changes in PR-interval, QRS-interval and QTc interval on the electrocardiogram. The findings in this study suggest that cardiotoxicity from mefloquine is unlikely. Bradycardia may be the result of autonomic control modulation after resolution of high fever.

Enzyme-linked immunosorbent assay based on monoclonal and polyclonal antibodies for the detection of Entamoeba histolytica antigens in faecal specimens

A murine monoclonal antibody (MAb) (Eh208C2-2) raised against crude lysate of the pathogenic HM-1:IMSS strain of Entamoeba histolytica was used in an enzyme-linked immunosorbent assay for the detection of E. histolytica antigens in faecal specimens. The detection limit of the assay was 110 and 280 amoebae/ml of the HM-1:IMSS and HK-9 strains in phosphate-buffered saline, respectively. The assay was applied to single stool samples from 3 groups of individuals comprising 40 patients whose stools were positive for E. histolytica trophozoites and/or cysts (group I), 48 patients whose stools were negative for E. histolytica but positive for other parasites (group II), and 36 parasitologically-negative healthy controls (group III). Positivity rates of 77.5%, 2.1% and 2.7% were found in samples from groups I, II and III respectively. Specificity, positive and negative predictive values, and efficiency of the assay were 97.6%, 93.9%, 90.1% and 91.1% respectively. When group I samples were further divided into a trophozoite-positive subgroup IA (13 samples) and a cyst-positive subgroup IB (27 samples), the positive rates were 100% and 66.7%, respectively (P < 0.025).

A national hospital-based survey of snakes responsible for bites in Thailand

Snakes which had been killed and brought to hospital with the patients they had bitten were collected in 80 district and provincial hospitals throughout 67 provinces in Thailand in order to establish the geographical distribution and relative medical importance of the venomous species. Of the 1631 snakes collected, 1145 were venomous: Malayan pit vipers (Calloselasma rhodostoma), green pit vipers (Trimeresurus albolabris) and Russell's vipers (Daboia russelii) were the most numerous, while T. albolabris, C. rhodostoma and spitting cobras ('Naja atra') were the most widely distributed. In 22 cases, non-venomous species were mistaken for venomous ones and antivenom was used unnecessarily. The Malayan krait (Bungarus candidus) was confused with B. fasciatus in 5 cases and B. fasciatus antivenom was used inappropriately. The study extended the known ranges of most of the medically-important venomous species in Thailand. Correct identification of venomous snakes is especially important in Thailand because the locally-produced antivenoms are monospecific. The technique of hospital-based collection, labelling and preservation of dead snakes brought by bitten patients is recommended when rapid assessment of a country's medically important herpetofauna is required.

The treatment of neurocysticercosis with praziquantel

Twenty-five patients with cerebral cysticercosis admitted to the Bangkok Hospital for Tropical Diseases from March 1987 to November 1989 were studied. The patients had a mean age of 41 +/- 5 years with a mean body weight of 57 +/- 4 kgs. Male to female ratio was 1.5:1. Eight patients (32%) gave a history of having taeniasis with a mean duration of 3.6 years before having symptoms of cerebral cysticercosis. Six patients (24%) also had subcutaneous cysticercosis with a duration of 20 +/- 8 months. The important clinical symptoms were headache, focal seizure, epilepsy and dementia. Fourteen patients (56%) had headache, 12 patients (48%) had focal seizure and four patients (16%) had a mild degree of dementia. Baseline study included routine blood examination, biochemical tests, cerebrospinal fluid for routine examinations and immunological study. Biopsy of subcutaneous cysts, plain films of soft tissue and computerized tomography of brain. Praziquantel was given orally at a dosage of 45 mg/kg/day in 3 divided doses at 4-5 hour interval for 15 days. Patients who were taking anti-epileptic drugs before were permitted to continue their medications. The evaluation of results of treatment was done a year post treatment, ten patients (40%) were asymptomatic, 12 patients (48%) had much clinical improvement, their epileptic attack was controlled by 1-2 tablets of phenobarbital (1/2 g) at bedtime. Two patients (8%) had mild headache. One patient (4%) was not improved. Those patients with dementia were not improved.(ABSTRACT TRUNCATED AT 250 WORDS)