[A survey on the epidemiological factors of clonorchiasis in the Pohang industrial belt along the Hyungsan river, Kyongsangbuk-do]

Prevalence of clonorchiasis in patients with gastrointestinal disease: A Korean nationwide multicenter survey

AIM: To investigate prevalence of Clonorchis sinensis in patients with gastrointestinal symptoms, and the relation of the infection to hepatobiliary diseases in 26 hospitals in Korea.

METHODS: Consecutive patients who had been admitted to the Division of Gastroenterology with gastrointestinal symptoms were enrolled from March to April 2005. Of those who had been diagnosed with clonorchiasis, epidemiology and correlation between infection and hepatobiliary diseases were surveyed by questionnaire.

RESULTS: Of 3080 patients with gastrointestinal diseases, 396 (12.9%) had clonorchiasis and 1140 patients (37.2%) had a history of eating raw freshwater fish. Of those with a history of raw freshwater fish ingestion, 238 (20.9%) patients had clonorchiasis. Cholangiocarcinoma was more prevalent in C. sinensis-infected patients than non-infected patients [34/396 (8.6%) vs 145/2684 (5.4%), P = 0.015]. Cholangiocarcinoma and clonorchiasis showed statistically significant positive cross-relation (P = 0.008). Choledocholithiasis, cholecystolithiasis, cholangitis, hepatocellular carcinoma, and biliary pancreatitis did not correlate with clonorchiasis.

CONCLUSION: Infection rate of clonorchiasis was still high in patients with gastrointestinal diseases in Korea, and has not decreased very much during the last two decades. Cholangiocarcinoma was related to clonorchiasis, which suggested an etiological role for the parasite.

Emerging foodborne trematodiasis

Foodborne trematodiasis is emerging because of increased aquaculture.

Foodborne trematodiasis is an emerging public health problem, particularly in Southeast Asia and the Western Pacific region. We summarize the complex life cycle of foodborne trematodes and discuss its contextual determinants. Currently, 601.0, 293.8, 91.1, and 79.8 million people are at risk for infection with Clonorchis sinensis, Paragonimus spp., Fasciola spp., and Opisthorchis spp., respectively. The relationship between diseases caused by trematodes and proximity of human habitation to suitable freshwater bodies is examined. Residents living near freshwater bodies have a 2.15-fold higher risk (95% confidence interval 1.38–3.36) for infections than persons living farther from the water. Exponential growth of aquaculture may be the most important risk factor for the emergence of foodborne trematodiasis. This is supported by reviewing aquaculture development in countries endemic for foodborne trematodiasis over the past 10–50 years. Future and sustainable control of foodborne trematodiasis is discussed.

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.

[Evaluation of sonography and skin test in diagnosis of clonorchiasis at the Hyongsan-gang (river) area]

This study was performed to evaluate diagnostic sensitivity and specificity of sonography on clonorchiasis. During the 9 months from March to November 1994, sonography, skin test, stool examination, and medical examination were performed to 609 volunteers of Pohang which is located along the Hyongsan-gang (River) and is one of well-known endemic areas of clonorchiasis. The sensitivity of sonography was either 21% if the intrahepatic ducts dilatation was assumed to be the only positive finding or 52% if the periductal echogenicity was also included as one of positive findings. The sensitivity of skin test was 62%. The sensitivity was 46% if the diagnostic criteria were arbitrarily assumed as being positive in skin test and having either sonographic findings. The sonographic finding of fusiform, non-shadowing, weakly echogenic foci in gallbladder or in biliary tree indicating the flukes or aggregates of flukes was not obvious in this study. The specificity of sonography was either 95% if the intrahepatic ducts dilatation was assumed to be the only positive finding or 82% if the periductal echogenicity was also included as one of positive findings. The specificity of skin test was 52%. The specificity was 90% if the diagnostic criteria was arbitrarily assumed as being positive in skin test and having either sonographic findings.

[Second report on intestinal parasites among the patients of Seoul Paik Hospital (1984-1992)]

The results of fecal examination for helminth eggs and protozoan cysts in Seoul Paik Hospital during 1984-1992 are reported. Fecal specimens of a total of 52,552 out- or inpatients were examined by formalin-ether sedimentation and/or direct smear method. The overall egg positive rate of helminths was 6.5% and the cyst positive rate of protozoa 2.5%. The egg positive rate (number of positive cases) for each species of helminth was; Clonorchis sinensis 3.2% (1,667), Trichuris trichiura 2.0% (1,089), Metagonimus yokogawai 1.2% (613), Ascaris lumbricoides 0.2% (100), Trichostrongylus orientalis 0.1% (34), Taenia spp. 0.05% (28), Hymenolepis nana 0.03% (18), hookworms 0.03% (17), Paragonimus westermani 0.02% (12), Echinostoma spp. 0.03% (12), Enterobius vermicularis 0.02% (10), Strongyloides stercoralis (larvae) 0.01% (6), and Diphyllobothrium latum 0.004% (2). The cyst positive rate (number of positive cases) for each protozoan was; Entamoeba coli 1.1% (588), Endolimax nana 0.8% (402), Giardia lamblia 0.3% (173), Entamoeba histolytica 0.3% (164), and Trichomonas hominis (trophozoites) 0.004% (2). Viewing from the data of 9 years, it was evident that the prevalence of soil-transmitted helminths such as A. lumbricoides and T. trichiura has been decreasing remarkably, while that of snail-transmitted helminths such as C. sinensis and intestinal protozoans has not.

Intestinal parasite infections in the inhabitants along the Hantan River, Chorwon-gun

The prevalence of intestinal parasite infections in inhabitants at the reaches of the Hantan River, Chorwon-gun, Korea, was observed from August 12 to September 14, 1993. Of 465 people observed by cellophane thick smear and formalin-ether concentration method, 2 Ascaris lumbricoides (unfertilized), 1 Trichuris trichiura, 39 Clonorchis sinensis and 16 Metagonimus egg positive cases were found. After treatment, the Metagonimus egg positive cases passed out flukes of Metagonimus Miyata type. Of 68 fish caught in the Hantan River, 14 (20.6%) were infected with metacercariae of Metagonimus, while no metacercaria of C. sinensis was found. At this area, soil-transmitted nematodes are very low, but clonorchiasis and metagonimiasis are prevalent by modernate endemicity.

[Current status and the changing pattern of the prevalence of clonorchiasis in the inhabitants in Sanchong-gun, Kyongsangnam-do, Korea]

This study was conducted to evaluate the current endemicity and the transition mode of the Clonorchis infection in Sanchong-gun Kyongsangnam-do. The areas of investigation, villages and schools surveyed, method and techniques used in this study were the same as in 1984. The egg positive rate of clonorchiasis in the general population of Sanchong-gun was 37.6% out of 837 examined persons. In the schoolchildren, the rate was 9.7% out of 145 persons examined. In the intensity of the infection among the cases, the mean EPG (Egg per gram of feces) in the inhabitants and schoolchildren were 3,310 (male 4,221, female 1,978) and 711 (male 620, female 833), respectively. Of the inhabitants with clonorchiasis, the cases of light infection (EPG < 1,000) and moderate infection (1,000 < EPG < 10,000) were 93.9%. The proportion with experience of eating raw freshwater-fish was 90.5% among the infecteds. Out of 138 inhabitants examined in both 1984 and 1992, the number of the positives by both examinations was 31 (22.5%), positive to negative conversion was 35 (25.4%), negative to positive conversion was 22 (15.9%). The present results reveal that there are no changes of the egg positive rate of clonorchiasis among inhabitants in Sanchong and the eating habit of raw freshwater-fish persists there. In this community, the eating habit is the most important problem to be solved for control of this endemic disease.

Turnover of biliary epithelial cells in Clonorchis sinensis infected rats

We performed bromodeoxyuridine (BrdU) staining to observe the proliferation pattern of epithelial cells on the biliary mucosa in Clonorchis sinensis infection. Albino rats were infected with 100 metacercariae each and their livers were processed for histopathological observation after BrdU injection. Five to six sites in the liver of a rat were selected for paraffin section, and stained immunohistochemically to visualize BrdU incorporating cells. The flukes were mainly in the common bile duct and right or left hepatic bile ducts. The proportion of stained epithelial cells in the infected bile ducts where the worms were found on the section was 2.9-10.2% at 1 week after infection, 7.3-12.8% at 2 weeks, 7.3-13.4% at 5 weeks, and 8.4-14.8% at 15 weeks while in the non-infected ducts 0 to 2.7% cells were stained. The stained cells were mainly at the base of the mucosal layer. It is suggested that mucosal epithelial cells of the bile ducts infected with C. sinensis become hyperplastic mainly by direct and local stimulation of the worms.

Secretions of the biliary mucosa in experimental clonorchiasis

The histological change of the biliary mucosa in clonorchiasis is characterized as adenomatous hyperplasia, and cross-sectioned mucosa looks like intestinal mucosa. In addition to the glandular hyperplasia, the metaplasia of mucin secreting cells is also known. The present study investigated the presence of intestinal secretion from the biliary mucosal cells of rabbits and rats with Clonorchis sinensis infection. The rabbit was infected with 300 and the rat was infected with 100 metacercariae of C. sinensis. A part of the animals were followed up after praziquantel treatment. The rabbit livers were prepared for histochemistry to observe any endocrine secretion and the bile duct mucosa of the mice was processed for the activity of brush border membrane (BBM)-bound enzymes of the small intestine. Immunohistochemistry with the polyclonal antibodies and biotin-streptavidin-peroxidase staining kit showed no positive cells for gastrin and secretin, but a few cells were positive for serotonin. The proliferated biliary mucosa of the mice revealed no activity of disaccharidases and aminopeptidase. Only alkaline phosphatase activity was found both in the control and the infected. The hyperplastic biliary mucosal cells showed no gastrointestinal secretory functions. The serotonin secreting cells may be one of the inflammatory cells.