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).

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.

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.

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.

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.

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%).