Risk factors for Opisthorchis viverrini infection among schoolchildren in Lao PDR.

A matched-pair case-control study was conducted to identify factors associated with Opisthorchis viverrini infection among primary schoolchildren to develop preventive education. A house-to-house interview of the guardians of 118 children (59 cases and 59 controls) was conducted to collect information about theirs and their children's fish eating habits of 10 locally available fish species. The guardians' knowledge and attitudes about Opisthorchis viverrini infection and socio-economic status were asked about. The frequencies of eating fish did not differ between cases and controls. However, cases ate raw fish more frequently than controls (5.1 vs 1.2 times monthly). The frequency of eating raw "pa-xiew" was most strongly related to infection (OR 2.47; 95%CI 1.05-5.82). Infection was significantly associated with the children's experiences of eating raw fish (OR 7.48; 95% CI 1.45-38.69), frequency of eating raw fish by their guardians (OR 1.26; 95% CI 1.04-1.53) and maternal educational and career (OR 0.76; 95% CI 0.62-0.94). To prevent infections it is necessary to prevent the fish from becoming infected and to avoid eating raw fish. Education should focus on the children and their guardians to promote better eating habits.

Incidence and risk factors of Opisthorchis viverrini infections in a rural community in Thailand.

Opisthorchis viverrini infection is one of the major public health problems in Thailand. Although information about transmission of this parasite to humans is well established, infections are still prevalent in the northern and northeastern Thailand. Thus, prospective epidemiologic information is needed for developing more effective public health interventions. A cohort study to identify incidence and risk factors of O. viverrini infection was conducted in a rural community in Thailand during December 2002-February 2004. The incidence rate of opisthorchiasis was 21.6/100 person-years. The independent factors associated with opisthorchiasis were an age > 60 years and consuming chopped raw fish salad (Koi pla). Thus, avoiding this raw fish salad should be emphasized in the national control program.

Biliary liver flukes (Opisthorchiasis and Clonorchiasis) in immigrants in the United States: often subtle and diagnosed years after arrival.

BACKGROUND: Biliary liver flukes are extremely common parasites in some regions of the world where consumption of raw fresh-water fish is a cultural practice. Clonorchis sinensis and Opisthorchis spp. are the major biliary liver flukes associated with human disease. Some of these parasites are highly associated with cholangiocarcinoma. It was noted that several cases presenting at our center had been in the US for prolonged periods. This prompted us to retrospectively review cases of liver fluke infection diagnosed at our facility. METHODS: All cases of biliary liver fluke infection over a 6-year period were retrospectively investigated at a clinic serving international patients, to determine the prevalence and risk factors for infection in a nonendemic area. Cases were identified through review of stool ova and parasite (O&P) records maintained at Regions Hospital/HealthPartners microbiology laboratory. All O&P samples positive for Opisthorchis spp. or Clonorchis sinensis were included in the review. RESULTS: Seventeen cases were identified during the study period. Our center performed approximately 1,800 stool O&P examinations per year on approximately 1,100 individuals per year during the study period. Biliary liver flukes were uncommon, accounting for 1.3% of individuals infected with organisms considered to be potentially pathogenic. Infections were predominantly found in migrants from Laos, Cambodia and Thailand. Cases were also identified in migrants from the former Soviet Union and South America. It is of note that 25% of patients were detected after 5 years of residence in the US. Often, the only clinical clue to infection was a mild absolute eosinophilia (500 to 1000 microL). CONCLUSIONS: Although biliary liver fluke is an infrequent cause of infection in immigrants to the US, because of the potential long-term consequences of chronic infection, educational information highlighting routes of infection and the fact that asymptomatic infection is common and may eventually lead to cancer should be aimed at high-risk community members and those who have been visiting friends and relatives in endemic areas.

[The pathomorphosis of opisthorchiasis]. / Patomorfoz opistorkhoza.

Based on the data available in the literature and their own findings, the authors have come to the conclusion that the clinical picture of opisthorchiasis has undergone profound changes in the past decades, which may be regarded as a manifestation of induced and reduced pathomorphism. Uninduced pathomorphism appears as decreased invasion rates and as acute forms. Induced pathomorphism shows up in reduced invasion or by timely liquidation of invasion. The etiological and pathogenetic role of Helicobacter pylori in the development of the gastroduodenal pathology in patients with opisthorchiasis is considered as a manifestation of false pathomorphism.

[Experimental models of combined tuberculosis-opisthorchiasis pathology]. / Eksperimental'nye modeli sochetannoi patologii tuberkulez--opistorkhoz.

An experimental model of the combined course of tuberculosis and opisthorchiasis is presented in the following variants: pulmonary tuberculosis-chronic opisthorchiasis, acute and chronic opisthorchiasis in combination with tuberculosis contamination, BCG and opisthorchiasis. Specific changes in the combined pathology are shown which differ from those that accompany each of the nosological forma. Data obtained in bacteriologic, parasitologic, immunologic and pathomorphologic studies were used to describe characteristic features of the models. The results obtained allow a suggestion that parasitocenosis of mycobacteria and Opisthorchis organisms has an influence on the pathogenesis, clinical picture, diagnosis, treatment, epidemiology and prevention of tuberculosis-opisthorchiasis combined pathology.

[Functional destabilization of the cell membranes in the pathogenesis of opisthorchiasis]. / Funktsional'naia destabilizatsiia kletochnykh membran v patogeneze opistorkhoza.

Lipid peroxidation (LPO) and antioxidant system have been studied in 28 patients with acute opisthorchiasis, 129 patients with chronic opisthorchiasis, 57 patients in the residual stage of the disease (6-12 months later) and 28 practically healthy subjects. The data obtained indicate excessive accumulation of primary (diene conjugates), secondary (malonic dialdehyde) and terminal (Schiff bases) LPO products in erythrocyte membranes of patients with acute and chronic opisthorchiasis. These patients have also revealed a drop in alpha-tocopherol level in erythrocyte membranes and blood plasma. An excessive content of primary and terminal LPO products persisted in erythrocyte membranes in the residual stage of the disease. Blood plasma alpha-tocopherol level remained low.

Opisthorchis viverrini: pathogenesis of infection in immunodeprived hamsters.

Opisthorchis viverrini infections were established in immunologically intact and T cell deprived hamsters. T cell deprivation appeared to have no effect on worm establishment or egg production. Histopathologically, intact and deprived animals showed similar degrees of bile duct hyperplasia and periductular fibrosis, though there was a marked reduction in the intensity of the periportal inflammation in the majority of T cell deprived animals. Serum transaminase levels were significantly raised in intact animals by 25 days after infection, whilst levels remained within normal limits throughout the infection period for the majority of the T cell deprived animals. The antibody response to parasite antigens as determined by immunoelectrophoresis, was impaired in T cell deprived animals. Attempts to correlate the serological picture with transaminase levels at three time points after infection and also with the extent of periductular inflammation seen on killing, proved largely unsuccessful. These results indicate that T cell deprivation of the hamster host ameliorates the periductular inflammatory response provoked by O. viverrini in this species. It is suggested that such inflammatory responses are evoked by parasite antigens which gain access to portal tract and surrounding areas, and that such reactions are immunopathological in their outcome to the host, resulting in liver cell death and subsequent replacement of resolving inflammatory and necrotic areas with fibrotic tissue.

Morbidity in relation to intensity of infection in Opisthorchiasis viverrini: study of a community in Khon Kaen, Thailand.

A study of the prevalence and intensity of opisthorchiasis viverrini in relation to morbidity as determined by standard medical examination was carried out in Nong Ranya, a small village containing 309 people in northeastern Thailand. Opisthorchis viverrini infection as determined by Stoll's quantitative egg count method had an overall prevalence of 94% and reached 100% prevalence in most age groups above the age of 10 years. With respect to intensity, 6% were uninfected, 26% had light (less than or equal to 1 eggs per mg [epmg] of feces), 37% moderate (greater than 1-10 epmg), 25% heavy (greater than 10-50 epmg), and 5% very heavy (greater than 50 epmg) infections. Peak intensity in both males and females occurred at age 40 and above. A history of eating "koipla" (a sauce consisting of ground up raw fish), of feeling weak, and of having right upper quadrant abdominal pains occurred most frequently in the infected groups and was correlated with intensity of infection. Regardless of intensity of infection, only a small proportion of the population were unable to carry out their routine activities. Anorexia, nausea or vomiting bore little relationship to the presence or intensity of infection. Hepatomegaly at the mid-clavicular line occurred in 14% of the population, mainly in the more heavily infected groups. Neither jaundice nor splenomegaly was observed in the population.

[Biological aspects of the problem of opisthorchiasis]. / Biologicheskie aspekty problemy opistorkhoza.

The paper reports the latest data concerning genesis and structure of opisthorchiasis area; biology, ecology, position in the system and distribution of the first intermediate hosts of Opisthorchis felineus; peculiarities of infections with Opisthorchis of the first and second intermediate hosts. The methods of chemical control of mollusks, the first intermediate host of Opisthorchis, are discussed.