Search

Reported is the seasonal pattern of Opisthorchis viverrini metacercariae in cyprinoid fish in north-east Thailand. Samples of fish were collected in 1991-92 at monthly intervals from two areas -- Khon Kaen Province, where the opisthorchiasis transmission rate was high, and Mahasarakham Province, where the rate was low. Metacercarial loads in both study areas had similar seasonal patterns. High burdens occurred in the late rainy season and winter (July to January) with low burdens during the summer (March to June). The average burden for Puntius leiacanthus in Khon Kaen was 1.68 metacercariae per fish (127.43 per kg), higher than for all species of cyprinoid fish from the low transmission area. The intensities of infection among P. leiacanthus and Cyclocheilichthys armatus collected in Mahasarakham were comparable, but lower than the intensity of Hampala dispar (0.75 metacercariae per fish) concurrently sampled from the same area (P [is less than] 0.05). There was no significant difference in metacercarial load per kg between fish species from Mahasarakham. The results indicate that seasonal variation in metacercariae was a common phenomenon in areas with both high and low endemicity of infection. Also, the metacerarial load in fish was positively associated with infection levels among humans., Introduction Foodborne trematode infections are important in Asia and some parts of Europe, and affect at least 17 million people (1). Opisthorchis felineus affects about 1.5 million in the former [...]

The levels of correlation between the number of Opisthorchis viverrini eggs excreted in the faeces and levels of anti-Opisthorchis IgG and IgG4 in the serum and urine (as indicated by absorbances in ELISA) have recently been evaluated in north–eastern Thailand. The 225 subjects investigated in detail, all of whom came from an endemic village in Chaiyaphum province, were selected on the basis of the numbers of O. viverrini eggs that they were excreting. ELISA based on a crude antigen extract of the trematode were then used to determine the levels of specific IgG and IgG4 in serum and urine samples. Compared with the egg-negative, the villagers who were found to be egg-positive for O. viverrini had significantly higher levels of specific IgG in their urine and serum and significantly higher levels of specific IgG4 in their serum. The serum levels of specific IgG and IgG4 and the urine levels of specific IgG all correlated with the numbers of O. viverrini eggs/g faeces [with correlation coefficients (r) of 0.251, 0.121 and 0.142, respectively]. Although the serum levels of IgG were positively correlated with the urine levels of IgG (r=0.098), there was no significant relationship between the serum and urine levels of specific IgG4 (r=0.051). When the 225 subjects investigated in the ELISA were divided according to whether they had no detectable Opisthorchis eggs in their faeces (N=57), or 1–100 (N=154), 101–1000 (N=5), 1001–1500 (N=5) or >1501 (N=4) eggs/g faeces, the serum and urine levels of specific IgG and the serum (but not urine) levels of specific IgG4 were also found to correlate significantly with the infection-intensity categories (with r-values of 0.550, 0.146 and 0.578, respectively). When the results of the faecal examinations were treated as the 'gold standard', the ELISA for the detection of (Opisthorchis-specific) serum IgG, serum IgG4, urine IgG and urine IgG4 had sensitivities of 99.2%, 23.1%, 43.0% and 45.9% and specificities of 93.0%, 29.6%, 45.9% and 67.2%, respectively. Although the study was limited by the small number of subjects with intense infections, it appears worth investigating urine samples for subclasses of specific IgG other than IgG4. [ABSTRACT FROM AUTHOR]

Eggs of most species digenean flukes hatch in the external environment to liberate larvae that seek and penetrate a snail intermediate host. Those of the human liver flukes, Opisthorchis viverrini, hatch within the gastrointestinal canal of their snail hosts. While adult parasites are primarily responsible for the pathology in cases of human opisthorchiasis, their eggs also contribute by inducing granulomata and in serving as nidi for gallstone formation. In view of the peculiar biology of O. viverrini eggs and their contribution to pathology, we investigated embryogenesis in this species by light and transmission electron microscopy. Egg development was traced from earliest stages of coalescence in the ootype until full embryonation in the distal region of the uterus. Fully mature eggs were generally impermeable to resin and could not be examined by conventional electron microscopy methods. However, the use of high-pressure freezing and freeze-substitution fixation of previously fixed eggs enabled the internal structure of mature eggs, particularly the subshell envelopes, to be elucidated. Fertilization occurs in the ootype, and the large zygote is seen therein with a single spermatozoon wrapped around its plasma membrane. As the zygote begins to divide, the spent vitellocytes are pushed to the periphery of the eggs, where they progressively degrade. The early eggshell is formed in the ootype by coalescing eggshell precursor material released by approximately six vitelline cells. The early eggs have a thinner eggshell and are larger than, but lack the characteristic shape of, mature eggs. Characteristic shell ornamentation, the "muskmelon" appearance of eggs, appears after eggshell polymerization in the ootype. Pores are not present in the shell of O. viverrini eggs. The inner and outer envelopes are poorly formed in this species, with the outer envelope evident beneath the eggshell at the opercular pole of the mature egg. The miracidium has a conical anterior end that lacks the distinctive lamellar appearance of the terebratorium of other digeneans, such as the schistosomes. The miracidium is richly glandular, containing an apical gland in the anterior end, large cephalic gland, and posterior secretory glands. Each gland contains a secretory product with different structure. The paucity of vitelline cells associating with eggs, the reduced size of eggs, and reduced complexity of the extraembryonic envelopes are interpreted as adaptations to the peculiar hatching biology of the miracidia.

Opisthorchiasis is the major public health problem in the endemic areas of Thailand and Laos because Opisthorchis viverrini infection causes serious hepatobiliary diseases including CCA. The molecular mechanism of the CCA carcinogenesis induced by the infection remains obscure. To reveal the potential genes and signaling pathways to involve in the carcinogenesis, the present study investigated the expression of c-Ski, an oncogene, and two TGF-β signaling pathway relative genes, TGF-β and Smad4, during the development of CCA induced by O. viverrini infection in hamster model, and in human opisthorchiasis associated CCA. The results showed that the expression of c-Ski gene was greatly up-regulated during the carcinogenesis of CCA in hamster model. The overexpression of c-Ski was confirmed by immunohistological staining result which showed the increased expression of c-Ski protein in cytoplasm of the epithelial lining of hepatic bile ducts. Moreover, the immunohistological staining of the specimens of human opisthorchiasis associated CCA revealed the up-regulated expression of c-Ski and Smad4 proteins in the cytoplasm of the epithelial lining of hepatic bile ducts and stomal fibrosis respectively. The expression of TGF-β and Smad4 were up-regulated, which expression kinetics was time-dependent of CCA development. These results suggest that c-Ski is likely involved in the carcinogenesis of CCA induced by O. viverrini infection through regulating TGF-β signaling pathway.

Concomitant immunity and its consequence against infection play roles in regulating worm burdens in helminthiasis. Under natural conditions, this immunity is generated by exposure to repeated low dose or trickle infection. In this study, concomitant immunity was induced in mice exposed repeatedly to infection with Echinostoma malayanum and its protective effect on a challenge infection evaluated. A profile of worm burden from exposure to 10 metacercariae/mouse/week rose rapidly during the first 2 weeks reaching a plateau from week 3 to 8 post infection. Based on a cumulative dose of infection, worm recoveries were around 75% in the first 2 weeks, dropped to 50% at week 3 and 19% at week 8. After week 2, adult worm burden was constant and no juvenile worms were found after week 3 of the experiment. To examine the effect of resistance against reinfection, mice in the experimental group were primarily infected with 10 metacercariae/week for 5 weeks, treated with praziquantel and were challenged with 75 metacercariae/animal. The number of worms recovered from the experimental groups was significantly lower than that from naïve control groups beginning from 24 h to 28 days post challenge. The worms in the experimental group showed growth retardation and the proportion of adult worms was lower than that in the control animals especially during the first 3 weeks of the experiment. Parasite fecundity was also suppressed compared with that in the control group. The selective effects of protective immunity on establishment, growth, and fecundity of challenged worms affected the population dynamics of E. malayanum which is a similar phenomenon to concomitant immunity in schistosomiasis., (Copyright © 2011 Elsevier Inc. All rights reserved.)

The present study investigated the effect of curcumin, a phenolic compound with yellow color from Curcuma longa L., on the expression of the apoptosis-related genes [BAX (Bcl-2 associated protein X), PKB, p53, MDM2 (mouse double minute 2), caspase 9, c-Ski, smad1 and smad4] in hamster opisthorchiasis. On Opisthorchis viverrini infection treated with dietary curcumin apoptosis-related gene expression profiles were similar to O. viverrini-infected group, but the expression levels seemed lower. Light microscopic observation revealed that aggregation of inflammatory cells surrounding the hepatic bile ducts in the groups infected with O. viverrini and treated with dietary curcumin was lower than in infected group. The intensity of the response is correlated with expression of the genes studied. The results suggest that curcumin reduces pathogenesis in hamster-opisthorchiasis by controlling apoptosis-related gene expression.

The curcumin compound from turmeric is effective in the treatment of many inflammatory diseases. The aim of our present study was to evaluate the efficacy of turmeric on reducing the histopathological changes of hamster opisthorchiasis. Hamsters were infected with Opisthorchis viverrini and then administered turmeric. Using light microscopic observation, liver function tests for alanine transaminase (ALT), alkaline phosphatase, and direct bilirubin were investigated. The resulting histopathological changes show that turmeric has anti-inflammatory properties--during both N-nitrosodimethylamine administration and O. viverrini infection--by reducing the aggregation of inflammatory cells surrounding the hepatic bile ducts, which correlates with a decreased serum ALT level. The decrease in direct bilirubin levels in the hamsters treated with turmeric suggests that turmeric may enhance biliary contraction. The present study found that turmeric clearly reduces the inflammatory cells in hamster opisthorchiasis at an early stage. This finding may be connected with a reduction in the risk factors of cholangiocarcinoma development.

Prevalences and intensity of infection with Angiostrongylus cantonensis third stage larvae were examined in mollusks to determine whether they are potential intermediate hosts in eight provinces, northeast Thailand. Mollusk samples were collected from 24 reservoirs (3 reservoirs/province) in close to human cases during the previous year. Six out of 24 localities and 9 (3 new record species) out of 27 species were found with the infection. The highest intensity in infected species was found to be only one or two snails, whereas the majority had very low or no infection. The highest density was found in Pila pesmei and the lowest in Pila polita. The edible snails, P. polita, P. pesmei, and Hemiplecta distincta have the potential to transmit A. cantonensis to man. The varying density levels of larvae in infected snails may reflect observed variation in symptoms of people who traditionally eat a raw snail dish.

Six groups (15 snails/group) of Pomacea canaliculata and Pila polita were infected orally with 0 (control), 200, 400, 800, 1600 and 3200 first-stage Angiostrongylus cantonensis larvae (L1). The respective mean+/-SD third stage larvae (L3) worm recovery 1-month post-infection (p.i.) for P. canaliculata was 0, 1.4+/-5.42 (0.7%), 0.13+/-0.35 (0.03%), 0.07+/-0.26 (0.009%), 0.07+/-0.26 (0.004%), 0, and for P. polita 0, 64.33+/-21.38 (32.25%), 115.36+/-36.82 (28.93%), 265.33+/-90.01 (33.27%), 471.33+/-92.98 (29.60%) and 849.00+/-243.23 (26.61%). The susceptibility of A. cantonensis in P. polita was dose-dependent (p<0.001). In the three groups (nine snails/group) of P. polita given 500 L1, we studied the distribution of L3 in the internal organs (i.e., foot, head+esophagus, kidney, albumin gland, mantle, intestine, digestive gland) and found the highest density after 1, 2 and 3 months p.i. in the mantle at 29.37%, 31.09% and 37.45%. The infection rate in P. canaliculata was too low to study distribution rates.

The levels of correlation between the number of Opisthorchis viverrini eggs excreted in the faeces and levels of anti-Opisthorchis IgG and IgG(4) in the serum and urine (as indicated by absorbances in ELISA) have recently been evaluated in north-eastern Thailand. The 225 subjects investigated in detail, all of whom came from an endemic village in Chaiyaphum province, were selected on the basis of the numbers of O. viverrini eggs that they were excreting. ELISA based on a crude antigen extract of the trematode were then used to determine the levels of specific IgG and IgG(4) in serum and urine samples. Compared with the egg-negative, the villagers who were found to be egg-positive for O. viverrini had significantly higher levels of specific IgG in their urine and serum and significantly higher levels of specific IgG(4) in their serum. The serum levels of specific IgG and IgG(4) and the urine levels of specific IgG all correlated with the numbers of O. viverrini eggs/g faeces [with correlation coefficients (r) of 0.251, 0.121 and 0.142, respectively]. Although the serum levels of IgG were positively correlated with the urine levels of IgG (r=0.098), there was no significant relationship between the serum and urine levels of specific IgG(4) (r=0.051). When the 225 subjects investigated in the ELISA were divided according to whether they had no detectable Opisthorchis eggs in their faeces (N=57), or 1-100 (N=154), 101-1000 (N=5), 1001-1500 (N=5) or >1501 (N=4) eggs/g faeces, the serum and urine levels of specific IgG and the serum (but not urine) levels of specific IgG4 were also found to correlate significantly with the infection-intensity categories (with r-values of 0.550, 0.146 and 0.578, respectively). When the results of the faecal examinations were treated as the 'gold standard', the ELISA for the detection of (Opisthorchis-specific) serum IgG, serum IgG(4), urine IgG and urine IgG(4) had sensitivities of 99.2%, 23.1%, 43.0% and 45.9% and specificities of 93.0%, 29.6%, 45.9% and 67.2%, respectively. Although the study was limited by the small number of subjects with intense infections, it appears worth investigating urine samples for subclasses of specific IgG other than IgG(4).

Genetic variation in Opisthorchis viverrini adults originating from different locations in northeast Thailand and Laos, People's Democratic Republic (PDR), was examined using random amplified polymorphic DNA (RAPD) analyses. In an initial analysis, the genomic DNA of one fluke from each of ten localities was amplified using 15 random primers (10-mers); however, genetic variation among O. viverrini specimens was detected reliably for only four primers. A more detailed RAPD analysis using these four primers was conducted on ten individuals from nine localities. Considerable genetic variation was detected among O. viverrini from different geographical areas and among some individuals from the same collecting locality. Comparison of the RAPD profiles revealed that O. viverrini adults from Laos PDR were genetically distinct from those from northeast Thailand. The taxonomic significance of this finding needs to be explored in more detail. The RAPD markers established in the present study provide opportunities to examine the biology and epidemiology of O. viverrini and fish-borne trematodes within the region. Additionally, application of these markers in such studies could have important implications in relation to the prevalence of cholangiocarcinoma in different regions of Asia.

Cross-sectional surveys of parasitic infection were performed using the agar plate culture technique (APCT) and modified formalin-ethyl acetate concentration technique (MFECT) to assess the true prevalence of Strongyloides stercoralis relative to other parasites in north-east Thailand. The enzyme-linked immunosorbent assay (ELISA) for diagnosis of S. stercoralis infection was used to estimate the seroprevalence for comparison with coproprevalence. Faecal and serum samples were collected from study participants during October-November 2000. Within the sample population of 332 rural northeast Thais from 3 communities, S. stercoralis was the most common parasitic infection (average 28.9%, range 27.7-30.3%) as determined by APCT; by MFECT the average was 5.4% (range 1.8-8.6%). Other intestinal parasites by order of prevalence were Opisthorchis viverrini (average 14.2%, range 8.6-19.4%), hookworm (average 12.3%, range 4-20.2%), Echinostoma sp. (7.5%), Giardia intestinalis (0.9%), Trichuris trichiura (0.6%), and Taenia sp., Hymenolepis nana and Entamoeba coli (all 0.3%). In an analysis of a subset of the sample population for which serum samples were available (n = 120), coproprevalence by APCT was 33.3% (range 27-53.8%) and seroprevalence was 47.5% (range 29.7-57.9%) by modified unit-based ELISA and 34.2% (range 21.6-42.1%) by conventional optical density (OD)-based ELISA. Taking APCT as the reference method for diagnosis of strongyloidiasis, the sensitivity and specificity of the OD-based ELISA were 65% and 81.3%, respectively, and of the unit-based ELISA were 77.5% and 71.3%, respectively. Our results indicate that S. stercoralis is the predominant parasite in rural north-east Thailand, and that APCT and ELISA should be used as complementary diagnostic methods for community-based parasite surveys, at least among those in high-risk groups.

The mitochondrial cytochrome c oxidase subunit I (CO I) gene and the second internal transcribed spacer region (ITS II) gene of Opisthorchis viverrini were compared among O. viverrini from various areas in northeast Thailand. The nucleotide sequences of partial CO I gene (417 bp) of O. viverrini differed among O. viverrini originated from Ubon Ratana, Leongpleuy, Ban Phai, Maha Sarakham, and Chatturat. These intraspecific variations were classified into 5 patterns but no area-specific pattem was observed. Amino acid sequence deduced from the nucleotide sequences of these genes was identical. Nucleotide sequences of a region of the O. viverrini ITS II gene (296 bp) from different areas were identical. However, they were different from those of Clonorchis sinensis, Haplorchis taichui, H. pumilio, Fasciola gigantica, Echinostoma malayanum and Centrocestus sp..