Prevalence of Opisthorchis viverrini infection among villagers harboring Opisthorchis-like eggs

The precise occurrence of Opisthochis viverrini infection in humans, who were positive for Opisthorchis-like eggs in a stool examination, was determined using the potassium permanganate staining method. In the 68 specimens examined, there were more individual O. viverrini eggs (38.24%) than singular Haplorchis taichui eggs (29.41%). One-fourth of the total specimens contained a mixed infection of O. viverrini and H. taichi eggs. The median ratio of O. viverrini: H. taichui eggs in mixed infection cases was 2.29 (min = 1, max = 17.5). It is suggested that chemotherapy with praziquentel treatment should be given to patients who are positive for O. viverrini-like eggs.

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.

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.

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.

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.

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].

Trematode infections. Opisthorchiasis, clonorchiasis, fascioliasis, and paragonimiasis

The parasitic diseases of the liver and lung are caused by trematodes or flukes--Opisthorchis viverrini, O. felineus, Fasciola hepatica, and Paragonimus westermani. Humans get infected by eating the second intermediate host of the fluke, for example, fish, crab, or water plant. The disease runs a chronic course. The diagnosis is made by the recover of eggs in stools or sputum, or by serodiagnosis. Praziquantel is the drug of choice except in falcioliaisis.

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.

Detection of Opisthorchis viverrini antigens in stools using specific monoclonal antibody

Detection of Opisthorchis viverrini antigens in stools using specific monoclonal antibody. International Journal for Parasitology 22: 527-531. A sandwich enzyme-linked immunosorbent assay (ELISA) was developed for detecting Opisthorchis viverrini antigen in faecal extracts of four groups of individuals. These were 24 patients with O. viverrini infection only (group 1), 31 patients with O. viverrini and other parasitic infections (group 2), 141 patients with other parasitic infections (group 3) and 21 normal, parasite-free individuals (group 4). The first antibody used in the ELISA was polyclonal immunoglobulin G prepared from the serum of a rabbit previously immunized with crude extract of O. viverrini. The second antibody was monoclonal antibody specific to an antigen located in the worm tegument and muscular tissue. Sensitivity of the assay was 31% while specificity was 100%. Considerations for improving the sensitivity are discussed.

Specific monoclonal antibodies to Opisthorchis viverrini

A Balb/c mouse was immunized with a crude soluble antigen of Opisthorchis viverrini adult worms (OVAA) over a period of 7 months. Spleen cells from the immune mouse were fused with Sp2/0 myeloma cells. Among the 264 tissue culture wells containing the fused cells, cells of 96 wells (36%) produced antibodies to the immunizing agent. Antibodies produced by cells in several wells reacted with antigens from other species of parasite. Cells of 17 wells produced antibodies specific only to OVAA, thus cells from three representative wells were cloned by limiting dilution. Hybrids obtained produced antibodies which could be classified according to their tissue specificities into three groups. The first group of antibodies reacted strongly to the worm integument and weakly with the muscles while those belonging to the second group reacted only to muscles of the worms. The monoclonal antibodies of the third group gave a positive reaction to both muscles and tegument.

Tumour markers in the detection of opisthorchiasis-associated cholangiocarcinoma

Opisthorchiasis is a major public health problem in north-east Thailand, where over 7 million inhabitants are reported to be infected. A significant percentage of infected individuals develops cholangiocarcinoma terminally, which is rapidly fatal. To determine whether certain tumour markers are elevated in Thai patients with cholangiocarcinoma, and thus might be useful in the diagnosis of cholangiocarcinoma associated with opisthorchiasis in Thailand, the tumour markers CA125 and CA19-9 were measured by radioimmunoassay in 94 serum samples. The subjects consisted of 52 patients admitted for non-gastroenterological diseases, 7 patients with histologically proven cholangiocarcinoma, 7 patients with clinically suspected cholangiocarcinoma, and 28 patients with uncomplicated opisthorchiasis. The mean levels (+/- standard deviation [SD]) of CA19-9 and CA125 in the controls were 12.5 +/- 10.2 and 24.7 +/- 11.1 units/ml respectively. Using the mean + 3SD as the cut-off level, 57.1% of patients with confirmed cholangiocarcinoma had elevated CA19-9 and 28.6% had elevated CA125. In patients with clinically suspected cholangiocarcinoma, 71.4% had elevated CA19-9 and 28.6% had elevated CA125. Among opisthorchiasis patients, 3.6% had elevated CA125 and none had elevated CA19-9. 1.9% of controls had elevated CA19-9 and none had elevated CA125. When positivity of either CA125 or CA19-9 was used as an indicator of malignancy, the sensitivity and specificity of the combined tests reached 85.7% and 98.1% respectively. These preliminary results suggest that the measurement of CA125 and CA19-9 may be useful in the early detection of opisthorchiasis-associated cholangiocarcinoma.

Fecal egg output in relation to worm burden and clinical features in human opisthorchiasis

A study of the relation of fecal egg excretion to worm burden and clinical features was carried out in 45 opisthorchiasis patients who had no signs of biliary obstruction. The fecal egg excretion was consistent and correlated with the worm burden. Although there was no definite association between clinical signs and intensity of infection, mild hepatomegaly and thickened wall or dilatation of the gallbladder were found more commonly in heavily infected patients. Eosinophilia was observed more often than previous reports. Concomitant parasitic infections were found in 82% of the patients. After praziquantel treatment, egg counts increased greatly during the first few days then decreased to very low levels in 7 days.

Human pathology of Opisthorchis viverrini infection: a comparison of adults and children

The pathology of human opisthorchiasis in 22 adults (20 to 68 years) and 7 children (7 to 15 years) at autopsy is described. The changes of the liver in adults and children are similar and are summarized as follows: Enlargement of the liver was a common finding. Pericholangitis was observed in most cases. The pathology was confined to the large and medium-sized bile ducts where the flukes inhabited. The small interlobular bile ducts had minimal or unremarkable changes. Dilatation of the bile ducts with hyperplasia, desquamation and proliferation of the bile duct epithelial cells, glandular formation and fibrous connective tissue infiltration of the walls were the most common features. The pathological changes were well established within 7 to 15 years. Dilatation of the gallbladder, chronic cholecystitis and carcinoma were found only in adults. Eight of ten cases were cholangiocarcinoma and two were hepatocellular carcinoma.

Ultrasonographic study of the biliary system in opisthorchiasis patients after treatment with praziquantel

Ultrasonographic examination of the liver and biliary system using a portable ultrasound unit was performed in 1987 in 647 opisthorchiasis patients who had been treated with praziquantel during 1981 to 1986. Treatments was repeated annually in those reinfected. The reinfection rate was 53.9% in the first year and gradually declined. Ultrasonographic findings were normal in 80.6% of subjects. The most common abnormal finding was liver enlargement (14.8%), followed by dilatation of the gallbladder (3.5%), sludge formation (2.1%) and thickening of the wall of the gallbladder (1.0%). Gallstones were found in 7 cases (1.0%). Dilatation of intrahepatic bile ducts was detected in one subject (0.1%). The incidence of gallstones in treated patients was similar to that reported in a large necropsy series of the general population. Prospective studies will be needed to further investigation the association between opisthorchiasis, treatment and gallstone formation.

Opisthorchis viverrini eggs and adult flukes as nidus and composition of gallstones

Three cases of opisthorchiasis with calculous cholecystitis was presented. The diagnosis of gallstones was made before praziquantel therapy in 2 cases, and 4 years after treatment in one case. The patients underwent cholecystectomy. Numerous O. viverrini eggs and one dead fluke were found in the bile in one case. A single stone was recovered from each gallbladder. All stones contained O. viverrini eggs. Fragments of flukes were also present in two cases. The stones consisted of a mixture of bilirubin pigment and calcium salts.

Incidence of bacteremia in patients with opisthorchiasis during recurrent cholangitis

A total of 257 haemocultures were performed in 50 patients with opisthorchiasis when they presented signs and symptoms of biliary tract infection. 19 patients showed positive haemoculture. There are no significant relationship between the age of the patient and the incidence of positive haemoculture. Septic shock occurred in 5 patients, one patient died. Out of 221 aerobic cultures, 14% were positive and of the 36 anaerobic cultures 11% were positive. The most common organism was Staphylococcus followed by Klebsiella and Bacillus spp. Anaerobic bacterias were Streptococcus spp. Clostridia spp. was not found in this study. Most organisms were sensitive to cefotaxime, cephalothin, kanamycin and chloramphenicol, and the least sensitive to ampicillin.

Albendazole in the treatment of strongyloidiasis

Albendazole was used to treat 30 patients with Strongyloides stercoralis infections. There were 21 males and 9 females, 13 to 68 years of age, who were divided into two groups of 11 and 19, respectively. Repeated pre- and post-treatment stool examinations were done by simple direct smear and formalin-ether concentration, and larval quantitations were done by the Stoll and Sasa's technique. Group I patients were given albendazole in dosages of 400 mg/day in divided doses for 3 days. Group II patients were given similar dosages, but were treated again 7 days later on the same schedule. Patients in Group I were followed for 14 days and those in Group II for 30 days. The cure rates were 73% for Group I and 100% for Group II. Side effects were minimal and transient. Albendazole is recommended for the treatment of strongyloidiasis in dosages of 400 mg/day in divided doses for 3 days with treatment repeated one week later.

Clinical features in severe opisthorchiasis viverrini

Clinical features of severe opisthorchiasis were studied in 88 patients. The ratio of males to females was 6.3 : 1; 75% were over 40 years old. The presenting symptoms were obstructive jaundice, 25% associated with secondary infection of biliary system; cholangitis and cholecystitis; intraabdominal mass, which was enlarged liver; 18% had palpable gallbladder; 18% had adenocarcinoma of the bile duct. High bilirubin was found in 46% of cases, high alkaline phosphatase in 80%; elevation of serum transaminase in 78% and low serum albumin in 62% of patients. There was no correlation between severity of the disease and the faecal egg output. The obstructive jaundice patients had low or no egg output. Two patients had no eggs in stool, but numerous Opisthorchis viverrini eggs and flukes were found in the gallbladder and bile ducts at operation.

Studies on the chemotherapy of human opisthorchiasis: effective dose of praziquantel in heavy infection

Ninety-six patients who had heavy Opisthorchis viverrini infection were studied. Egg count per gram of faeces ranged from 10,800 to 139,000 (mean 26,044.3). Praziquantel 50 mg per kg body weight was given after a morning meal. 68 patients completed the follow up period of 60 days. The cure rate was 97.0%. The side-effects occurred in 61 patients (89.7%). The common side effects were diarrhoea, dizziness, sleepiness, epigastric pain, headache, nausea and anorexia. These side-effects were mild and transient. 62 patients (91.2%) showed clinical improvement, and 20 patients were symptom free on day 60.

Clinical and laboratory evaluation of praziquantel in opisthorchiasis

A total of 122 patients were treated with a single dose of praziquantel 40 mg per kilogramme body weight, with 96 patients completing the follow up period of 60 days. The parasitological cure rate was 95.8% by single faecal examination. These patients had mild clinical manifestations. The hematological, biochemical and the liver function tests were within the normal limits. High eosinophilia was observed in 84.5% but there were no significant difference after eradication of the flukes. No significant changes were observed in the laboratory investigation at day 60 post treatment.