Control of clonorchiasis by repeated praziquantel treatment and low diagnostic efficacy of sonography

Cost yield of different treatment strategies against Clonorchis sinensis infection

BACKGROUND

Clonorchiasis is attributed to the ingestion of raw freshwater fish harboring Clonorchis sinensis. Morbidity control is targeted through the administration of antihelminthics. This study modelled the cost yield indicated by effectiveness and utility of different treatment strategies against clonorchiasis.

METHODS

About 1000 participants were enrolled from each of 14 counties selected from four provincial-level administrative divisions namely Guangxi, Guangdong, Heilongjiang and Jilin in 2017. Fecal examination was adopted to detect C. sinensis infection, while behavior of ingesting raw freshwater fish was enquired. Counties were grouped into four categories based on prevalence, namely low prevalence group (< 1%), moderate prevalence group (1-9.9%), high prevalence group (10-19.9%) and very high prevalence group (≥ 20%), while population were divided into three subgroups, namely children aged below 14 years old, adult female and adult male both aged over 14 years old. The average of cost effectiveness indicated by the cost to treat single infected cases with C. sinensis and of cost utility indicated by the cost to avoid per disability-adjusted life years (DALYs) caused by C. sinensis infection was calculated. Comparisons were performed between three treatment schedules, namely individual treatment, massive and selective chemotherapy, in which different endemic levels and populations were considered.

RESULTS

In selective chemotherapy strategy, the cost to treat single infected case in very high prevalence group was USD 10.6 in adult male, USD 11.6 in adult female, and USD 13.2 in children. The cost increased followed the decrease of endemic level. In massive chemotherapy strategy, the cost per infected case in very high prevalence group was USD 14.0 in adult male, USD 17.1 in adult female, USD 45.8 in children, which were also increased when the endemic level decreased. In individual treatment strategy, the cost was USD 12.2 in adult male, USD 15.0 in adult female and USD 41.5 in children in very high prevalence group; USD 19.2 in adult male, USD 34.0 in adult female, and USD 90.1 in children in high prevalence group; USD 30.4 in adult male, USD 50.5 in adult female and over USD 100 in children in moderate prevalence group; and over USD 400 in any population in low prevalence group. As to cost utility, the differences by treatment strategies, populations and endemic levels were similar to those in cost effectiveness.

CONCLUSIONS

Both cost effectiveness and cost utility indicators are highly impacted by the prevalence and population, as well as the treatment schedules. Adults especially men in the areas with a prevalence over 10% should be prioritized, in which selective chemotherapy was best and massive chemotherapy was also cost effective. In moderate endemic areas, the yield is not ideal, but selective chemotherapy for adult male may also be adopted. In low endemic areas, all strategies were high costly and new strategies need to be developed.

A Clonorchiasis Case of a Leopard Cat, Prionailurus bengalensis euptilurus, Diagnosed by Ultrasonography and Egg Detection in Republic of Korea

A clonorchiasis case in a captive leopard cat, Prionailurus bengalensis euptilurus, was confirmed by ultrasonographic findings and egg morphologies found in the bile juice sample in the Korea. The leopard cat was introduced from the wild habitat of Gyeongsangnam-do, to Cheongju Zoo in Cheongju-si, Chungcheongbuk-do, Korea in August 2014. Physical examinations were basically performed for quarantine and check-up health. The cat was comparatively good in health except anorexia. The cyst-like bile duct dilation and the increased echogenicity of gall bladder wall and hepatic parenchyma were observed by ultrasonography. Ultrasound-guided needle biopsy was conducted for collecting bile juice and the specimens were observed under light microscope. The numerous small trematode eggs were detected in the bile juice sample of the light microscopy. The eggs were 25–33 (28±3) μm by 18–22 (20±1) μm in size and showed typical characteristics of Clonorchis sinensis egg, i.e., a dominantly developed operculum, shoulder rim and dust-like wrinkles in surface. To treat the liver fluke infection, 20 mg/kg of praziquantel was orally administered only once to the case. Follow-up studies including fecal examinations were conducted during 2 years after treatment. But no more eggs were detected from the case. In the present study, we described the first clonorchiasis case of leopard cat, which was confirmed by ultrasonographic findings and egg morphologies from the bile juice sample in Korea.

Identifying Helminth Infections via Routine Fecal Parasitological Examinations in Korea

We conducted this study to explore the extent of occult helminth infection identified by fecal parasitological examinations or organ-specific examinations such as colonoscopy and abdominal ultrasonography (US) during health checkups. We analyzed 197,422 fecal samples from 99,451 subjects who received health checkups at a single center over 10 years. We found that 3,472 (1.8%) samples from 3,342 (3.4%) subjects tested positive for parasitic ova, including clonorchiasis, metagonimiasis, trichuriasis, ascariasis, trichostrongylosis, taeniasis, and enterobiasis. The detection rate for clonorchiasis was higher in those who were taking their first examination than in those who had been examined previously. The detection rate for clonorchiasis decreased gradually over the 10 years. Only 2.5% of the patients with clonorchiasis showed US or computed tomography (CT) images that were compatible with the disease. Clonorchiasis patients who had abdominal US or CT images that suggested clonorchiasis were older and had lower body mass indices and higher eosinophil counts than did those whose US or CT images did not suggest the disease. We observed worms in 9% of the patients with trichuriasis who had received a colonoscopy. Colonoscopy also uncovered adult worms in 0.03% of subjects who were not identified as having Trichuris trichiura ova in their fecal helminth examinations. In summary, our study shows that occult helminth infection is fairly frequently identified by a variety of methods during health checkups, which suggests that doctors need to make greater effort to identify and treat occult helminth infections in Korea.

Current status and perspectives of Clonorchis sinensis and clonorchiasis: epidemiology, pathogenesis, omics, prevention and control

Clonorchiasis, caused by Clonorchis sinensis (C. sinensis), is an important food-borne parasitic disease and one of the most common zoonoses. Currently, it is estimated that more than 200 million people are at risk of C. sinensis infection, and over 15 million are infected worldwide. C. sinensis infection is closely related to cholangiocarcinoma (CCA), fibrosis and other human hepatobiliary diseases; thus, clonorchiasis is a serious public health problem in endemic areas. This article reviews the current knowledge regarding the epidemiology, disease burden and treatment of clonorchiasis as well as summarizes the techniques for detecting C. sinensis infection in humans and intermediate hosts and vaccine development against clonorchiasis. Newer data regarding the pathogenesis of clonorchiasis and the genome, transcriptome and secretome of C. sinensis are collected, thus providing perspectives for future studies. These advances in research will aid the development of innovative strategies for the prevention and control of clonorchiasis.

Reprint of "An overview of freshwater snails in Asia with main focus on Vietnam"

Freshwater snails have received much attention for their role as intermediate hosts for trematodes causing disease in people and animals such as schistosomiasis and various food-borne trematodes. While effective medical treatment exists for some of these diseases there is need for preventive measures to reduce transmission, e.g. control of intermediate hosts because transmission patterns are often complicated due to presence of reservoir final hosts. In order to implement control measures against the intermediate host snails with minimal impact on the freshwater ecosystems and their biodiversity, a profound knowledge on transmission patterns of the trematodes is required and this is partly related to distribution, habitat preferences, and seasonal variation in density of the intermediate host species. Identification of snail species can be problematic on the basis of morphological and anatomical characters alone as some species show morphological plasticity and similarly morphological differentiation of cercariae found in snails may be difficult and this could lead to biased perceptions of intermediate host spectra and transmission patterns. In this paper, we give an overview of the snail families and their medical and veterinary importance in Asia but with main focus on Vietnam.

An overview of freshwater snails in Asia with main focus on Vietnam

Freshwater snails have received much attention for their role as intermediate hosts for trematodes causing disease in people and animals such as schistosomiasis and various food-borne trematodes. While effective medical treatment exists for some of these diseases there is need for preventive measures to reduce transmission, e.g. control of intermediate hosts because transmission patterns are often complicated due to presence of reservoir final hosts. In order to implement control measures against the intermediate host snails with minimal impact on the freshwater ecosystems and their biodiversity, a profound knowledge on transmission patterns of the trematodes is required and this is partly related to distribution, habitat preferences, and seasonal variation in density of the intermediate host species. Identification of snail species can be problematic on the basis of morphological and anatomical characters alone as some species show morphological plasticity and similarly morphological differentiation of cercariae found in snails may be difficult and this could lead to biased perceptions of intermediate host spectra and transmission patterns. In this paper, we give an overview of the snail families and their medical and veterinary importance in Asia but with main focus on Vietnam.

High reinfection rate after preventive chemotherapy for fishborne zoonotic trematodes in Vietnam

Background

The World Health Organization aims for complete morbidity control of fishborne zoonotic trematodes (FZT) in endemic areas by 2020. The main intervention tool for achieving this goal is regular use of preventive chemotherapy by offering praziquantel to those at risk in endemic areas. The purpose of this study was to investigate the effectiveness of preventive chemotherapy to control FZT in an endemic area in Northern Vietnam.

Methodology and principle findings

We followed a cohort of 396 people who fulfilled the criteria for receiving preventive chemotherapy. Stool samples were examined by Kato-Katz technique for the presence of trematode eggs before, and two, 16, 29 and 60 weeks after preventive chemotherapy. The prevalence of trematode eggs in stool was 40.2% before, 2.3% two weeks after and increased to a cumulative prevalence of 29.8% sixty weeks after preventive chemotherapy.

Conclusions

The effectiveness of preventive chemotherapy as a main component in control of FZT is not well documented in most endemic areas. We found a high reinfection rate within the first year after preventive chemotherapy. Since these trematodes are zoonoses, preventive chemotherapy may not have sufficient impact alone on the transmission to have a lasting effect on the prevalence. Animal reservoirs and farm management practices must be targeted to achieve sustainable control of fishborne zoonotic trematode infections, hence control programs should consider a One Health approach.

Fishborne zoonotic trematodes (FZT) are small parasitic flatworms (flukes) living either in the intrahepatic bile ducts or in the intestines of humans and many species of animals and birds. Transmission occurs by eating infected raw freshwater fish. FZT are especially common in Southeast and East Asia. WHO suggests using preventive chemotherapy in the control of these parasites by providing an effective drug, praziquantel, once a year to either all inhabitants in the endemic areas or selectively to those who are at special risk because they eat raw fish. Preventive chemotherapy has been used for some years in Northern Vietnam, but the effectiveness has not been thoroughly examined. We followed a group of 396 people who had eaten raw fish and examined the stool for the presence of trematode eggs before preventive chemotherapy and two, 16, 29 and 60 weeks after. The proportions of egg positive persons were 40.2% before, 2.3% two weeks after and increased to 29.8% sixty weeks after preventive chemotherapy. We found a high rate of reinfection. Contribution from animals to the transmission implies that preventive chemotherapy of humans alone will most likely be insufficient to control the FZT infections.

Prevalence and Risk Factors of Clonorchiasis among the Populations Served by Primary Healthcare Posts along Five Major Rivers in South Korea

Objectives:

Clonorchiasis is an infectious disease caused by the Chinese liver fluke Clonorchis sinensis. In this study, we investigated the prevalence and risk factors of clonorchiasis among the populations served by primary healthcare posts along five major rivers in South Korea.

Methods:

Forty primary healthcare posts that are located less than 5 km from one of the five rivers were selected from 26 counties. For the purpose of the survey, community health practitioners selected the nearest villages from the riversides in their own catchment area. From January to May 2009, a total of 2788 stool samples were collected and examined using the formalin–ether sedimentation technique. Village inhabitants were also interviewed by means of questionnaires in order to obtain information on potential risk factors.

Results:

The prevalence rates of clonorchiasis at various river basins were as follows: Seomjin River, 21.3%; Nakdong River, 13.5%; Geum River, 9.2%; Han River, 7.6%; and Yeongsan River, 4.9%. The total number of people infected with C. sinensis was 329 (11.3%). By gender, 14.3% of males and 7.6% of females were infected. In case of both males and females, the prevalence rate was highest in those in their 40s. Consumption of raw freshwater fish was confirmed as a risk factor based on a logistic regression analysis.

Conclusion:

The present findings suggest that clonorchiasis is still highly prevalent among the inhabitants of riverside areas in southern Korea, and, accordingly, it is necessary to implement a systematic control program in the endemic areas.

Effect of control strategies on prevalence, incidence and re-infection of clonorchiasis in endemic areas of China

Background

A pilot clonorchiasis control project was implemented to evaluate the efficacies of various chemotherapy strategies on prevalence, incidence and re-infection in Heilongjiang Province, China.

Methods and Findings

Seven intervention groups (14,139 residents, about 2000 in each group) in heavily or moderately endemic areas were subjected to repeated praziquantel administration from 2001 to 2004. In the selective chemotherapy groups, residents were examined for fecal eggs, and those who tested positive were treated with three doses of 25 mg/kg praziquantel at 5-hour-intervals in one day. However, all residents were treated in the mass chemotherapy groups. In heavily endemic areas, two mass treatments of all residents in 2001 and 2003 reduced the prevalence from 69.5% to 18.8%, while four annual mass treatments reduced the prevalence from 48.0% in 2001 to 8.4% in 2004. Selective annual treatments for egg-positive subjects reduced the egg-positive rates from 54.9% in 2001 to 15.0% in 2004 or from 73.2% in 2001 to 12.3% in 2004. Selective treatments every 6 months significantly reduced the prevalence from 59.5% in 2001 to 7.5% in 2004. All of the repeated treatments reduced EPG (eggs per gram of feces) significantly. The annual mass treatment and selective treatment every 6 months produced lower prevalence and re-infection rates and higher egg reduction rate than annual selective treatments did. In the moderate endemic areas, egg positive rates were 24.8% and 29.7% in 2001 but were 1.9% and 1.3% after 2 or 3 selective treatments. The prevalence, incidence, re-infection rates in a moderately endemic area were significantly lower than those of heavy endemic areas.

Conclusions

Repeated mass treatment or selective treatment with praziquantel every 6 to 12 months is highly effective for clonorchiasis control in heavily endemic areas. In contrast, one or two selective treatments with health education is effective in moderately endemic areas.

Clonorchiasis is a liver fluke disease prevalent in East Asia, which is transmitted to humans mainly by eating raw freshwater fish. It induces various complications in the liver or bile duct including cholelithiasis, cholecystitis, cholangitis, and cirrhosis. Clonorchis sinensis has been known to cause cholangiocarcinoma, and is still a major health problem in endemic areas. People in endemic areas are repeatedly infected with C. sinensis, as they continue to consume raw freshwater fish in spite of control activities and availability of a highly effective drug, praziquantel. Reservoir hosts such as cats, dogs, and pigs supply eggs continuously to the environment and act as a source of infection. The present study analyzed the data produced by the Korea-China collaborative project for helminthiasis control in China during 2001–2004 to find out effective chemotherapeutic control strategies with praziquantel in endemic areas and to evaluate their effects on the transmission of C. sinensis infection by repeated mass or selective treatment. The four-year control trial found that repeated treatment is essential to the effective reduction of prevalence and infection intensity in heavily endemic areas. Mass chemotherapy is more effective than selective treatment, and more repeated treatments produce better outcomes in clonorchiasis control. Health education to change the habit of consuming raw or undercooked fish is an important and practical measure to prevent and reduce human infections in endemic areas. Together with chemotherapy, health education could be highly effective and produce sustainable effects in clonorchiasis control. Treatment of reservoirs, if applicable, will contribute to reduce the source of infection.

Changes in sonographic findings after treatment of patients with clonorchiasis in a heavy endemic area

We measured changes in sonographic findings of patients with clonorchiasis after a treatment in a highly endemic area. A total of 347 residents showed positive stool results for Clonorchis sinensis eggs in a village in northeastern China, and were treated with praziquantel. Of them, 132 patients underwent abdominal sonography both before and 1 year after treatment, and the changes in sonographic findings of 83 cured subjects were compared. Diffuse dilatation of intrahepatic bile ducts (DDIHD) was found in 82 patients (98.2%) before and 80 (96.4%) after treatment, which was improved in 3, aggravated in 1, and unchanged in 79 patients. Increased periductal echogenicity (IPDE) was observed in 42 patients (50.6%) before and 45 (54.2%) after treatment, which was improved in 5, aggravated in 8, and unchanged in 70 patients. Floating echogenic foci in the gallbladder (FEFGB) was detected in 32 patients (38.6%) before and 17 (20.5%) after treatment, which was improved in 20, aggravated in 5, and unchanged in 58 patients. Improvement of FEFGB only was statistically significantly (P = 0.004). The present results confirm that DDIHD and IPDE persist but FEFGB decreases significantly at 1 year after treatment. In a heavy endemic area, the sonographic finding of FEFGB may suggest active clonorchiasis 1 year after treatment.

Collection of Clonorchis sinensis adult worms from infected humans after praziquantel treatment

A cohort was established for evaluation of cancer risk factors in Sancheong-gun, Gyeongsangnam-do, Korea. As one of the cohort studies, stools of 947 residents (403 males and 544 females, age range: 29-86 years) were screened for Clonorchis sinensis eggs using both Kato-Katz method and formalin-ether sedimentation technique. The overall egg positive rate of C. sinensis was 37.7% and individual EPG (eggs per gram of feces) counts ranged from 24 to 28,800. Eight egg positive residents voluntarily joined a process of collection of the passed worms after praziquantel treatment. A total of 158 worms were recovered from 5 of the 8 treated persons, ranged from 3 to 108 in each individual. The worms were 15-20 mm x 2-3 mm in size, and showed brown-pigmented, red, or white body colors. This is the first collection record of C. sinensis adult worms from humans through anthelmintic treatment and purgation. The adult worms of C. sinensis may be paralyzed by praziquantel and then discharged passively through bile flow in the bile duct and by peristaltic movement of the bowel.

Imaging diagnosis of clonorchiasis

Among several diagnostic tools for clonorchiasis (Clonorchis sinensis infection), radiologic examinations are commonly used in clinical practices. During the 2 past decades, many reports regarding imaging findings of clonorchiasis were introduced. The basic imaging finding of clonorchiasis is diffuse dilatation of the peripheral intrahepatic bile ducts, without dilation of the large intrahepatic or extrahepatic bile ducts. By this finding, however, active clonorchiasis cannot be differentiated from cured infection. Some recent radiologic studies suggested specific findings of active clonorchiasis. Besides direct demonstration of worms, increased periductal echogenicity on sonography and periductal enhancement on dynamic contrast-enhanced CT or MR imaging possibly represent active clonorchiasis. Those images of the liver clonorchiasis are known to be correlated with worm burdens (EPG counts) in their frequency and also severity. The images of cholangiocarcinoma associated with clonorchiasis show both the tumor with obstruction images and diffuse dilatation of the peripheral intrahepatic bile ducts. Radiological images can be a good practical alternative diagnostic method of clonorchiasis.

Therapeutic evaluation of sustained-releasing praziquantel (SRP) for clonorchiasis: phase 1 and 2 clinical studies

Sustained-releasing praziquantel (SRP) tablet was designed for single dose treatment regimen of clonorchiasis. A previous pre-clinical study confirmed its sustained-releasing characteristics and a better cure rate than conventional praziquantel (PZQ). In this clinical study, the pharmacokinetics of this SRP tablet were investigated in human volunteers (phase 1; 12 volunteers), and its curative efficacy was examined in clonorchiasis patients (phase 2; 20 volunteers). In the phase 1 clinical study, blood concentrations of both tablets showed wide individual variation. The AUClast of SRP was 497.9 +/- 519.0 ng * hr/ml (mean +/- SD) and PZQ of 628.6 +/- 695.5 ng * hr/ml, and the AUCinf of SRP was 776.0 +/- 538.5 ng * hr/ml and of PZQ 658.6 +/- 709.9 ng * hr/ml. Cmax values of SRP and PZQ were 90.7 +/- 82.2 ng/ml and 214.9 +/- 251.9 ng/ml, and Tmax values were 3.42 +/- 1.43 hr and 1.96 +/- 1.23 hr, respectively. SRP tablets showed similar AUC values, but lower Cmax and longer Tmax values than PZQ. In the phase 2 study, SRP at 30 mg/kg (single dose) achieved a 60% cure rate and a 95.5% egg reduction rate. The cure rate of a single dose SRP was unsatisfactory compared with that of the conventional PZQ dose, but much better than that achieved by a single dose PZQ.

A successful experience of soil-transmitted helminth control in the Republic of Korea

Soil-transmitted helminths (STH), namely Ascaris, Trichuris and hookworms (Ancylostoma and Necator), present a global health problem to about a half of the earthos population. In the Republic of Korea, STH were highly prevalent and were considered a high priority target for national control. To promote the control, a non-governmental organization named Korea Association for Parasite Eradication (currently Korea Association of Health Promotion) was founded in 1964, and mass fecal examination followed by selective mass chemotherapy with anthelmintics was performed twice a year from 1969 to 1995 targeting whole nationwide schoolchildren. Meanwhile, decreasing patterns of national STH infections have been monitored by 7 timeso quinquennial national surveys targeting general population. In 1971, the overall intestinal helminth egg positive rate was 84.3% (Ascaris 58.2%, Trichuris 65.4%, and hookworms 10.7%), which became 63.2% in 1976, 41.1% in 1981, 12.9% in 1986, 3.8% in 1992, 2.4% in 1997, and 4.3% (Ascaris 0.03%, Trichuris 0.02%, and hookworms 0%) in 2004. During the control period, national economy rapidly developed, and living standards including environment, sanitation, and agricultural technology greatly improved, which undoubtedly boosted the STH control effects. Our experience indicates that social driving force to establish an eligible national control system to conduct repeated mass chemotherapy, together with improvement of environment and sanitation, is important for initiating and achieving STH control in a developing community.

A DNA Vaccine Encoding a Fatty Acid-Binding Protein of Clonorchis sinensis Induces Protective Immune Response in Sprague-Dawley Rats

Clonorchis sinensis, the Chinese liver fluke, resides chronically in the biliary tract, and fatty acid-binding protein (FABP) is known to play an important role in the intracellular transport of long-chain fatty acids obtained from the host. Although FABP has stimulated considerable interest as a vaccine candidate, the nature of C. sinensis FABP (CsFABP) remains unclear. We investigated the immunogenicity and protective efficacy of a DNA vaccine encoding CsFABP. The intradermal injection of plasmid DNA carrying the CsFABP gene (pcDNA3.1-FABP) into Sprague-Dawley (SD) rats induced both humoural and cellular immune responses. Animals injected with pcDNA3.1-FABP developed FABP-specific antibody, which is dominance of IgG2a in sera. In addition, the DNA vaccine elicited the production of IFN-gamma, but not the production of IL-4 in spleen cells stimulated with recombinant FABP. Moreover, pcDNA3.1-FABP induced a significant level of protection, decreased worm burden (40.9%, P<0.05) in SD rats against C. sinensis metacerariae challenge. These results suggest that pcDNA3.1-FABP induces a typical T helper-1-dominated immune response and it is a good candidate for use in future clonorchiasis vaccination studies.

Clonorchiasis and cholangiocarcinoma: etiologic relationship and imaging diagnosis

Despite a gradual decrease in prevalence, clonorchiasis is still prevalent in East Asia. A large and compelling body of evidence links clonorchiasis and cholangiocarcinoma, although the mechanisms involved are not completely understood. Clonorchiasis induces biliary epithelial hyperplasia and metaplasia, and this could facilitate at least one stage of the carcinogenesis, which is promoting effect. In areas of endemic infection, more clonorchiasis cases are now diagnosed incidentally during radiological examinations such as cholangiography, ultrasonography, and computed tomography. Radiological findings are regarded as pathognomonic for clonorchiasis since they reflect the unique pathological changes of this disorder. These radiological examinations currently play important roles in the diagnosis, staging, and decision-making process involved in the treatment of cholangiocarcinoma. The morphological features and radiological findings of clonorchiasis-associated cholangiocarcinoma are essentially combinations of the findings for the two diseases. The morphological features of clonorchiasis- associated cholangiocarcinoma, observed in radiological examinations, do not differ from those of the usual cholangiocarcinoma. In patients diagnosed with or suspected to have clonorchiasis, radiological findings should be carefully scrutinized for occult cholangiocarcinoma.

Bile duct changes in rats reinfected with Clonorchis sinensis

This study describes an evaluation of the sonographic, cholangiographic, pathological, and immunological findings, and the protective effect shown by rats reinfected with Clonorchis sinensis. Eight experimental rat groups were, namely, a normal control, a primary infection control, a reinfection I (reinfection 7 week after treatment following 3-week infection), a reinfection II (reinfection 2 week after treatment following 8-week infection), a reinfection III (exploration of the intrahepatic bile ducts 1 week after reinfection 4 week after treatment following 4-week infection), a superinfection, a secondary infection control, and an infection following immunization group. Sonographic and cholangiographic findings showed moderate or marked dilatation of the bile duct confluence in the primary infection control, reinfection II, and secondary infection control groups. Juvenile worms survived in the intrahepatic bile ducts 1 week after reinfection following treatment in the reinfection III group. It was concluded that reinfecting juvenile worms found during the first week following reinfection failed to survive or grow further. Anatomical, pathophysiological, or immunological changes may induce protection from reinfection in rats.

Sonographic findings of active Clonorchis sinensis infection

PURPOSE

The aim of this study was to document the characteristic sonographic findings of clonorchiasis for the diagnosis of active infection in an endemic area.

METHODS

In a village in northeastern China, residents underwent fecal examinations for detection of Clonorchis sinensis eggs. Shortly thereafter, residents were examined with abdominal sonography. An experienced radiologist performed the sonographic examinations and analyzed the findings. Subjects whose fecal examinations were positive for eggs were considered to have active clonorchiasis; those whose examinations were negative for eggs were used as control subjects. The distinguishing sonographic features of active clonorchiasis were identified by stepwise logistic regression analysis.

RESULTS

The study population comprised 457 subjects; fecal examinations revealed C. sinensis eggs in 316 and no eggs in 141. Four sonographic findings distinguished subjects with active clonorchiasis from control subjects: increased periductal echogenicity (p < 0.001; R = 0.11; sensitivity, 35%; specificity, 91%), floating echogenic foci in the gallbladder (p < 0.001; R = 0.09; sensitivity, 28%; specificity, 94%), diffuse dilatation of the intrahepatic bile ducts (p < 0.01; R = 0.03; sensitivity, 67%; specificity, 48%), and gallbladder distention (p < 0.05; R = 0.02; sensitivity, 3%; specificity, 100%), in decreasing order of significance. Among these 4 sonographic findings, increased periductal echogenicity and floating echogenic foci in the gallbladder were more significantly associated with active infection than were the other 2.

CONCLUSIONS

Increased periductal echogenicity and floating echogenic foci in the gallbladder were identified as the 2 most significant findings for the sonographic diagnosis of active C. sinensis infection.

The Kato-Katz method is reliable for diagnosis of Clonorchis sinensis infection

We evaluated the sensitivity of three fecal examination methods, the Kato-Katz (KK) method, formalin-ether technique (FE) and direct smear, for the diagnosis of clonorchiasis. The KK method proved to be most sensitive in six groups with different egg counts. In cases of extremely light infection FE was found to be more sensitive than KK.

Sustained-release praziquantel tablet: pharmacokinetics and the treatment of clonorchiasis in beagle dogs

Praziquantel is rapidly absorbed and secreted; and thus fractional doses are recommended for the treatment of cestode and trematode infections. In the present study, we developed a new praziquantel tablet formula allowing sustained-release (SRP). In vitro dissolution of SRP tablets showed that praziquantel at 300 mg/tablet combined with hydroxypropyl methylcellulose dissolved completely at a constant rate over 10 h, whereas the conventional praziquantel tablet (PZQ) was only 40% dissolved. Pharmacokinetic studies in dogs confirmed that SRP was absorbed more slowly than PZQ. The mean value of the area under the concentration/time curve from 0 h to the final observation time, the maximum concentration in serum, and the time of maximum concentration in serum for SRP were 3,471,500 ng/min for 0.25 ml, 10,300 ng for 0.25 ml, and 192 min, while the values for PZQ were 688,600 ng/min for 0.25 ml, 2,500 ng for 0.25 ml, and 135 min. The cure rate in dogs with a heavy infection (500 metacercariae) treated with a single dose of SRP (150 mg/tablet) at 50 mg/kg was 80%, while in dogs treated with a single dose of SRP (300 mg/tablet) at 30 mg/kg it was 60%, and the cure rate with PZQ was 20%. In each case, the egg reduction rate was similar (over 90%). No abnormal liver functions or hepatic or renal pathologies were observed in dogs administered with SRP at 30 mg/kg. The SRP tablet showed sustained release and slow absorption; and it had an improved anthelmintic efficacy against Clonorchis sinensis in experimental dogs, compared with conventional praziquantel.

Experimental clonorchiasis in dogs: CT findings before and after treatment

PURPOSE

To determine whether disease activity in clonorchiasis can be assessed with dynamic computed tomography (CT).

MATERIALS AND METHODS

Ten dogs infected with metacercariae of Clonorchis sinensis underwent serial dynamic CT examinations. Five dogs were sacrificed 14 weeks after infection, and another five infected dogs were treated with praziquantel at the 14th week and continued to undergo CT examinations until death or sacrifice at the 25th (n = 1) or 40th week (n = 4). CT images were evaluated for dilatation of the bile ducts, contrast enhancement of bile duct walls and adjacent hepatic parenchyma, visualization of flukes within the bile ducts, and presence of calcifications. Changes in CT findings were analyzed statistically by using a mixed linear model and a generalized estimating equations model.

RESULTS

Dilatation of the bile ducts, contrast enhancement of the ductal walls, transient hepatic attenuation differences, and flukes per se were observed at CT from the 2nd through the 5th week, were most apparent between the 5th and 13th weeks, and disappeared or decreased markedly in degree after treatment in all dogs (P <.05). Nodular calcifications were observed at CT after treatment in two dogs. Histopathologic examination revealed proliferation and enlargement of arteries in the periductal area and the portal tracts and congestion of hepatic sinusoids during the acute phase. Treatment was associated with periductal hyalinization, degeneration of the periductal arteries, and calcification of the ductal epithelium.

CONCLUSION

Disease activity in experimental canine clonorchiasis can be assessed with dynamic CT.

Control of clonorchiasis by repeated treatments with praziquantel

The present study aimed to evaluate control efficacy of clonorchiasis by two schemes of repeated treatment with praziquantel at two endemic villages in China. Residents of one village at Guangxi Autonomous Region were treated and examined 6-monthly and of another at Liaoning Province 12-monthly. In residents that took 25 mg/kg x 3 (total 75 mg/kg) of praziquantel every 6 months for one year the egg positive rate showed a significant drop from 69.0% to 17.1%. In contrast, a group of same praziquantel medication once showed a slight marginal decrease in the egg rate from 18.9% to 12.2% after one year. Of 39 subjects examined 3 times, 56.4% were cured, 7.7% persistently positive, one (2.6%) reinfected after cure or newly infected, but 25.6% were persistently negative. The present finding suggests that 6-monthly medication with 75 mg/kg of praziquantel should effectively lower the prevalence but incomplete for control of clonorchiasis in heavy endemic areas.

Trematodes of the family Opisthorchiidae: a minireview

Examination of the original descriptions of genera placed within the family Opisthorchiidae has revealed that only 33 of the original 43 genera are valid members of this family. Further study of these descriptions should also reveal that many of the subfamilies are also invalid. With reference to the original descriptions of these genera, and subsequent literature, a brief survey of the family has been compiled. Information on the spectrum of definitive hosts that these helminths parasitize is provided, as well as information on the life cycles, geographic distribution, and socioeconomic impacts of the family. More in-depth information is given on those species that are of particular medical importance; namely, Clonorchis sinensis, Opisthorchis viverrini, and O. felineus. The final aims of this review are to provide information on the entire genera of the family Opisthorchiidae, which will aid understanding of the phylogenetic relationships not only within the family, but also within the Class Trematoda.

Long-lasting sonographic and histopathological findings in cured clonorchiasis of rabbits

To ascertain residual sonographic and histopathological findings of clonorchiasis after treatment, the present study evaluated sonographic findings in rabbits which were infected with 500 metacercariae of C. sinensis every 6 months for 18 months after treatment with praziquantel. The sonographic findings were analyzed in terms of intrahepatic bile duct dilatation and periductal echogenicity, and histopathological findings were observed after the last sonographic examination. Compared with the sonographic findings before treatment, dilatation of the intrahepatic bile ducts became mild to some degree in four of the seven cases and increased periductal echogenicity resolved in four of them. The histopathological specimens after 18 months showed that periductal inflammation has almost resolved but moderate dilatation of the intrahepatic ducts and mucosal hyperplasia persisted. The periductal fibrosis minimally resolved. The long-lasting sonographic findings in cured clonorchiasis make sonography less specific.