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PubMed2000

Infection status with trematode metacercariae in pond smelts, Hypomesus olidus.

Many Koreans usually eat raw pond smelts, Hypomesus olidus, in the winter. This study was performed to evaluate the infection status with trematode metacercariae in pond smelts from January 1998 through February 1999. Among 1,305 fish collected, 459 were purchased from wholesale dealers in Chinchon-gun, Chungchongbuk-do, and the rest of them were caught with a casting net in Soyangho (Lake), Taehoman (Bay) and Paekkokchosuchi (Pond). Seven species of trematode metacercariae including two unidentified ones were detected from 1,305 pond smelts. The number of detected trematode metacercariae according to the species are as follow: Clonorchis sinensis 8, Holostephanus nipponicus 7, Cyathocotyle orientalis 24, Diplostomum sp. 14, and Metorchis orientalis 7. From the above results, it was confirmed that H. olidus plays a role as the second intermediate host of some kinds of trematode including C. sinensis in Korea. Our report shows possible clonorchiasis caused by eating raw pond smelts.

Animals↗

PubMed2000

Spatial and temporal variation of trematode infection in coexisting populations of intertidal gastropods Littorina saxatilis and L. obtusata in the White Sea.

Trematode infection was studied in sympatric populations of the periwinkles Littorina saxatilis and L. obtusata in 2 regions of Kandalaksha Bay of the White Sea to assess host-parasite interactions at the population level. Twenty-seven spatially separated populations were each surveyed in 1984-1994; 2 heavily infected populations were investigated annually over a 16 yr period. Ten trematode species were found in the periwinkle populations. The closest association in spatial distribution and temporal dynamics was observed between 3 ecologically and morphologically similar trematodes of the 'pygmaeus' group: Microphallus piriformes, M. pygmaeus and M. pseudopygmaeus. For these 3 species, the prevalences were closely associated in the 2 host species when spatially separated sites from the 2 studied regions were considered, while in the 2 populations studied over the 16 yr period, a correlation was only observed between the infection levels of L. saxatilis and L. obtusata by either M. piriformes and immature microphallids. Likewise, within each host species, significant correlations were revealed between the prevalence of the different microphallids of the 'pygmaeus' groups. However, they were fewer and weaker when the long-term dynamics of infection in the 2 heavily infected populations were considered. Most other trematodes did not show significant association in prevalence either within or between the 2 host species on spatial and temporal scales.

Analysis of Variance↗

PubMed2002

[RAPD variation in two trematode species (Fasciola hepatica and Dicrocoelium dendriticum) from a single cattle population].

The method of random DNA amplification by PCR with arbitrary primers (RAPD-PCR) was used for the description and estimation of genetic variation in two trematode species, Fasciola hepatica (n = 21) and Dicrocoelium dendriticum (n = 8). The studied trematodes were liver parasites of five cattle individuals belonging to the same herd. To study the F. hepatica population, five primers were selected, which revealed 320 RAPD markers in five samples of parasites isolated from five different host individuals. Using 87 RAPD markers, a comparison of variation was conducted between F. hepatica and D. dendriticum samples from the same host individual. Based on the estimates of RAPD variation for the individual samples of parasites collected from each of five host individuals and for the total F. hepatica population, standard indices of genetic similarity (S), diversity (H), polymorphism (P), and population subdivision (FST) were calculated. From the indices of similarity in pairs (S), dendrograms were constructed, which reflect genetic relationship between the representatives of two species and between F. hepatica individuals isolated from the same or different host individuals. It was revealed that polymorphism level (P) varied within a range of 35.5 to 83.2% in the studied F. hepatica population and reached 95.1% in the studied D. dendriticum population. Two different trematode species that simultaneously parasitize the same host animal were characterized by similar estimates of polymorphism and genetic diversity and by similar topology of genetic similarity dendrograms. The degree of genetic similarity between F. hepatica and D. dendriticum was significantly lower (20%) than between five F. hepatica samples (41.4%) that formed two unequal clusters. Each of these clusters represents a heterogeneous group consisting of parasites collected from three or four host individuals. In the individual samples of parasites related to each of the studied host individuals, the indices of genetic similarity (S) and diversity (H) varied within a range of 43.3 to 64.8% and 25.1 to 56.6%, respectively. In the total F. hepatica sample, the estimates of intraspecific variation, the topology of dendrograms, and the FST index (7.4%) indicate the absence of clear genetic differentiation between the samples of parasites isolated from different host individuals. Possible reasons for the high level of genetic variation in the studied trematode populations and the genetic consequences of host--parasite interaction are discussed.

Animals↗

PubMedDate not supplied

[The microstructure of trematodes studied by electron microscopy].

The main tendencies in the studies into the ultrastructure of trematodes (including species of medical importance) using scanning and transmission electron microscopy are considered. Attention was paid to disproportions in the studies into the different developmental stages of trematodes: maritae are better studied than parthenogenetic and larval stages and especially eggs and miracidia. During the last years the number of studies using the complex of histochemical, radioisotope and electron microscopic methods is increasing, among them the investigations on the changes caused by modern anthelmintic agents in the tegument and viscera of trematodes. These are mainly the trematodes of Schistosomatidae, Echinostomatidae, Fasciolidae and Paragonimidae families that were studied by electron microscopy, and the studies on Opisthorchidae are very scarce.

Animals↗

PubMed1993

Trematode community structure in the pulmonate snail Physa gyrina.

Trematode community structure was examined in the pulmonate snail Physa gyrina over a 12-mo period. A total of 1,181 snails was collected from Charlie's Pond, North Carolina, and was found to be parasitized by 6 trematode species. Infracommunities were relatively species rich when compared to previous studies, with 18.4% of infected snails having multi-species infections. Halipegus eccentricus was found in 88.4% of multiple infections, usually with 1 of 2 other autogenic, egg-transmitted species (Haematoloechus complexus and Glypthelmins quieta). Neither negative interspecific interactions nor a dominance hierarchy were apparent among the trematodes. These factors, along with high snail vagility and the temporal heterogeneity of infective stages in the environment, are suggested to have contributed to the high number of multiple infections. Halipegus eccentricus was also the most prevalent parasite throughout the study, occurring in nearly 50% of all snails during May, June, and July. Apparent parasite-induced host mortality caused by this trematode species contributed to increasing species diversity in larger snails. The component community was also affected by the continuous recruitment of new snails into the host population and by changes in the number of infective stages present over time.

Animals↗

PubMed1997

Fasciola gigantica and F hepatica: a comparative study of some characteristics of Fasciola infection in Lymnaea truncatula infected by either of the two trematodes.

Experimental infections were carried out using three Lymnaea truncatula populations and two Fasciola species in order to determine the trematode influence on six parameters of snail infection by either of the two trematodes. All experiments were performed using snails 4 mm long, two miracidia for each L truncatula, and a constant temperature of 20 degrees C. No significant influence of trematode species was detected in the following parameters: snail survival at day 30, the life span of infected snails (from miracidial exposure to snail death), the increase in shell length throughout the experiment, the duration of the patent period and the number of cercariae shed by infected snails. The frequency of cercaria-shedding snails was closely correlated with the particular L truncatula population and trematode species. A similar finding in two populations was also noted for the frequencies found in the infected snails who died without emission. The prepatent period had a longer duration in the Fasciola gigantica-infected groups. The percentages of floating cysts were greater in the Fasciola gigantica groups than in the Fasciola hepatica groups.

Animals↗

PubMed2006

Do trematode parasites disrupt defence-cell signalling in their snail hosts?

More than a decade ago, it was postulated that components derived from trematode parasites block receptors on the defence cells of their snail intermediate hosts, thus preventing host-cell activation and parasite elimination. This phenomenon has still not been investigated extensively. However, recent work concerning the molecular regulation of the molluscan defence response provides a new framework for studies that focus on an extension of this original concept - subversion of host cell signalling by trematode parasites. The hypothesis is that, to facilitate survival and replication in their intermediate hosts, trematode parasites down regulate host defence responses by interfering with key signal-transduction pathways in snail defence cells.

Animals↗

PubMed2002

Presumed trematode-induced granulomatous anterior uveitis: a newly recognized cause of intraocular inflammation in children from south India.

PURPOSE: To describe the epidemiologic, clinical, and histopathologic features of a presumed trematode granulomatous anterior uveitis, primarily in children from south India. DESIGN: Prospective, noncomparative, case series. METHODS: Children with clinical evidence of granulomatous anterior uveitis were selected for the study. Those who presented with distinct anterior chamber nodules were evaluated. Demographic details, such as clinical findings and course of illness, were noted. Patients underwent either medical treatment or surgical aspiration of the lesion based on the size of the lesion. Aspirated materials were subjected to histopathologic analysis and cultures for bacteria and fungi. Response to treatment and final visual status were evaluated. RESULTS: One hundred thirteen patients with anterior chamber nodules were seen between 1998 and 2000. Ninety-three (82.4%) were males and 20 (17.7%) were females. The median age was 11.0 years. All patients were from south India and all gave a history of bathing or swimming in the local pond or river. All had normal systemic work ups. Of the 113 patients, 110 had anterior chamber nodules and three had both anterior chamber and subconjunctival nodules. Aspirates of the anterior chamber lesions revealed lymphocytes, intact and necrotic neutrophils, and eosinophils admixed with histiocytes. One subconjunctival nodule showed necrotizing granuloma, displaying the tegument of a trematode. Those patients who were followed had good visual recovery after medical or surgical intervention or both. CONCLUSION: The present study shows a newly recognized granulomatous anterior uveitis caused by a presumed water-borne trematode infection. This infection appears to be a common cause of pediatric granulomatous anterior uveitis in south India.

Adolescent↗

PubMed2001

An outbreak of trematode-induced granulomas of the conjunctiva.

PURPOSE: To describe the epidemiologic, clinical, and histopathologic features of trematode granulomas of the conjunctiva, eyelid, and anterior chamber in pediatric patients. DESIGN: Prospective noncomparative case series. PARTICIPANTS: Forty-one children from a southern Indian village with conjunctival granulomas. METHODS: The village of Sellananthal was selected for a field visit after analysis of earlier hospital-based allergic conjunctival granuloma cases. Children with ocular diseases were examined, and histories of exposure to assumed risk factors and clinical findings were evaluated. Selected patients were brought to the base hospital for excisional biopsy. Serial sections obtained from the excised nodules were examined for the presence of a parasite. MAIN OUTCOME MEASURES: Histopathologic examination of excised conjunctival lesions or response of lesions to local medical therapy. RESULTS: In this year-long prospective study, 41 children (16 years or younger; 38 boys and 3 girls) with clinical features of allergic conjunctival granulomas were examined. Thirty-four patients were from a single village located in the southern Indian state of Tamil Nadu; the remaining 7 were from various parts of the same state. All children swam in their village's freshwater pond. Twenty patients with nodules less than 5 mm in diameter received medical treatment; 13 with larger nodules underwent surgical excision of the lesions. Nine of these 13 cases revealed a zonal granulomatous inflammation admixed with eosinophilic leukocytes; 4 of these 9 displayed fragments of the tegument and internal structures of a trematode and Splendore-Hoeppli phenomenon. The remaining 4 of the 13 cases revealed nongranulomatous inflammation made up of lymphocytes, histiocytes, and eosinophils. Eight patients refused surgical treatment. CONCLUSIONS: In southern India, one cause of allergic conjunctival granulomas in children seems to be trematode infection. The clustering of cases in a single village and exposure to a village freshwater pond indicate the need for an epidemiologic investigation and study of the parasite's life cycle. Sporadic cases from other parts of the state with similar histories of exposure to their local pond or river water suggest a widespread distribution of the etiologic agent.

Adolescent↗

PubMed2004

Chemotherapy for major food-borne trematodes: a review.

Food-borne trematode infections, caused by liver flukes (Clonorchis, Fasciola, Opisthorchis), lung flukes (Paragonimus) and intestinal flukes (Echinostoma, Fasciolopsis, heterophyids), are significant public health problems, most notably in Southeast Asia and the Western Pacific. Globally, it is estimated that > 40 million people are infected among the 750 million people who live in endemic areas. The epidemiology of food-borne trematodiasis has changed over the past few decades, and now presents a dual picture. On the one hand, increasing numbers of infections are reported from non-endemic areas, and endemic areas are expanding due to larger areas utilised for aquaculture, domestic migration, declining socioeconomic conditions, lack of improved sanitation, and increasing availability of aquatic foods through wider distribution networks often without proper food inspections. On the other hand, social and economic advances in many Asian countries, going hand-in-hand with urbanisation, use of chemical fertilisers and, above all, the administration of safe, efficacious and inexpensive drugs, have significantly reduced the prevalence of food-borne trematode infections. In this review, the taxonomy, life cycle, and geographical distribution of the major food-borne trematodes, including issues of diagnosis and clinical disease manifestations, is summarised. The discovery, chemistry, pharmacological properties, safety, therapeutic efficacy and adverse effects of the current drugs of choice, namely praziquantel and triclabendazole, is then discussed. Recent advances on other drugs and contemporary investigations on novel compounds that might become important players in chemotherapy are highlighted. Finally, the need for research and development of new trematocidal drugs that - employed in concert with health education, improved sanitation and enhanced food safety - are key factors for sustainable control of food-borne trematodiasis, is highlighted.

Animals↗

PubMed2006

Rearing density and susceptibility of Rana pipiens metamorphs to cercariae of a digenetic trematode.

Cercariae of many digenean trematodes target particular developmental stages of their hosts. For some digeneans that are parasites of amphibians, infection appears timed to host metamorphosis. The success and timing of metamorphosis is itself affected by a number of factors, including host density. We investigated the degree to which rearing density of Rana pipiens larvae influenced time to metamorphosis and snout-to-vent length and mass at metamorphosis, as well as establishment of cercariae of the trematode Manodistomum syntomentera Stafford, 1905. As expected, individuals metamorphosed later, were smaller, and weighed less at metamorphosis if they were reared under intermediate to high densities compared with low densities, in experimental outdoor mesocosms. Cercariae establishment was higher in smaller metamorphs that took longer to metamorphose within the low-density treatment. Additionally, cercariae establishment was lower in larvae from the low-density tanks compared with larvae from the intermediate- to high-density tanks. However, more tadpoles had failed to metamorphose in the intermediate to high rearing densities by the time cercariae were no longer available from natural collections of first intermediate hosts, Physa spp. Larval amphibians under crowded conditions should experience increased susceptibility to trematode establishment in nature, but only if they metamorphose within the time period when cercariae are still available.

Analysis of Variance↗

PubMed2006

Infection status of pond smelts, Hypomesus olidus, and other freshwater fishes with trematode metacercariae in 6 large lakes.

In order to determine the current infection status of pond smelts, Hypomesus olidus, and other freshwater fishes with trematode metacercariae, a total of 4,861 pond smelts and 18 other freshwater fishes, collected from the Soyang and Uiam Lakes in Gangwon-do, the Unam Lake in Jeollabuk-do, the Jangseong Lake in Jeollanam-do, the Uirim-ji (lake) in Chungcheongbuk-do, and the Andong Lake in Gyeongsangbuk-do, were individually digested with 1% pepsin-HCl and examined under a dissecting microscope. In all pond smelts caught from the 6 lakes, we were unable to detect any known human infectious trematode metacercariae in Korea. However, in other freshwater fishes, such as, Squalidus japonicus coreanus (Unam Lake), and Zacco platypus (Jangseong Lake) and Opsariichthys uncirostris amurensis (Jangseong Lake), metacercariae of human-infecting trematodes, i.e., Clonorchis sinensis and Metagonimus sp. were detected, respectively.

Animals↗

PubMed2005

Epidemiology and control of trematode infections in cattle in Zimbabwe: a review.

In this paper the main epidemiological aspects of the major domestic ruminant trematode infections in Zimbabwe are reviewed and discussed with regard to the available options for control. Seasonal occurrence of amphistomes, Fasciola gigantica and Schistosoma mattheei are considered both in the definitive and intermediate hosts. The regional distribution of the trematodes is reviewed in relation to the distribution patterns of their snail intermediate hosts. Based on the epidemiological features of the trematodes, practical control measures are suggested.

Age Factors↗

PubMed2003

The food-borne trematode zoonoses of Vietnam.

During the past couple of decades, numerous surveys for the occurrence and distribution of food-borne trematodes in Vietnam have been carried out. However, the majority of the data obtained have not been published in international journals, and therefore, the seriousness of these trematode parasitic zoonoses in the country has not been fully appreciated. To correct this, over 40 Vietnamese language reports and local publications were translated and organized as a status review for an international audience. The results show that such serious trematode zoonoses as clonorchiasis, opisthorchiasis, paragonimiasis and fascioliasis are common in many regions of Vietnam, and, in the case of fascioliasis and paragonimiasis, are increasing. Data on the species of intermediate hosts involved in the transmission of these zoonoses, and the effect of host sex and age on infection frequencies are presented, along with findings on food preference/behavior investigations. Finally, the authors present recommendations for further research to provide a more comprehensive picture of the status of these zoonoses, and to obtain the risk assessment information needed to design prevention and control programs.

Adolescent↗

PubMedDate not supplied

[The effect of trematodes on the cellular immunity of the dragonfly Aeschna grandis (Odonata) larvae].

The high percent of the infestation by the trematodes of the families Plagiorchidae and Prosthogonimidae is recorded in the dragonfly Aeschna grandis larvae of the last stage. About 30% of the trematode cysts were melanized. It is established, that the parasitising of the trematodes do not effects on the process of the incapsulation of foreign bodies, but it suppresses partly the formation of oxygen free radicals and phenoloxidase activity in the haemocytes of dragonfly larvae.

Animals↗

PubMed2006

Spatial covariation between infection levels and intermediate host densities in two trematode species.

Both theoretical arguments and empirical evidence suggest that parasite transmission depends on host density. In helminths with complex life cycles, however, it is not clear which host, if any, is the most important. Here, the relationships between the abundance of metacercariae in second intermediate hosts, and the local density of both the first and second intermediate hosts of two trematode species, are investigated. Samples of the snail Potamopyrgus antipodarum, the amphipod Paracalliope fluviatilis and the isopod Austridotea annectens were collected from ten stations in a New Zealand lake. In the trematode Coitocaecum parvum, neither the density of the snail first intermediate host nor that of the amphipod second intermediate host correlated with infection levels in amphipods. In contrast, in the trematode Microphallus, infection levels in isopod second intermediate hosts were positively associated with isopod density and negatively associated with the density of snail first intermediate hosts. These relationships are explained by a negative correlation between snail and isopod densities, mediated in part by their different use of macrophyte beds in the lake. Overall, the results suggest that, at least for Microphallus, local infection levels depend on local intermediate host densities.

Amphipoda↗

PubMed1989

Some trematodes of freshwater fishes from North Vietnam with a list of recorded endohelminths by fish hosts.

The present paper comprises a systematic survey of trematodes collected from 12 species of freshwater fishes from North Vietnam (the Red River near Hanoi). Altogether 16 trematode species (14 adults and 2 juvenile forms) have been recorded. These include: Amurotrema dombrowskajae, Platycladorchis microacetabularis, P. macroacetabularis, Neocladorchis multilobularis, Carassotrema koreanum, Azygia hwangtsiyui, Phyllodistomum clariasi, Phyllodistomum sp., Orientocreadium batrachoides, Masenia collata, Bucephalopsis ozakii, Dollfustrema bagarii sp. n., Prosorhynchus vietnamensis sp. n., Prosorhynchus sp. juv., Metadena bagarii sp. n., and Isoparorchis hypselobagri juv. Except for the first four named species, all the trematodes are briefly described and illustrated and some problems concerning their taxonomy and geographical distribution are discussed. D. bagarii sp. n. from Bagarius bagarius (catfish) is characterized mainly by location of the mouth opening in anterior half of body, extension of the uterus anteriorly not surpassing vitellaria, number of spines (about 60) on the rhynchus, and by other features. Characteristic features of P. vietnamensis sp. n. (host B. bagarius) are the structure and shape of the rhynchus, equatorial situation of vitellaria, postequatorial distribution of gonads and mouth opening, extension of the uterus, and body measurements, whereas those of M. bagarii sp. n. (host B. bagarius) include the shape (spherical) of the ovary, extent of caeca (slightly surpassing testes) and body measurements. Carassotrema ginezinskajae Kulakova et Ha Ky, 1976 is considered a junior synonym of C. koreanum Park, 1938. Eight species have not yet been reported from Vietnam. The findings include several new host records.

Animals↗

PubMed1989

[Resistance to drought of mollusks of the genus Bulinus, vectors of human and animal trematode infections in Senegal. II. Study under natural conditions in the North-Sudan area. Ecology and resistance to drought of Bulinus umbilicatus and B. senegalensis].

The authors report on the results of a 2-year study on the ecology and resistance to drought of B. umbilicatus and B. senegalensis on 3 temporary ponds in the North-Sudan area (region of Tambacounda, Senegal). The variations in some abiotic factors like the temperature and the pH of water do not seem to have a strong influence on the ecology while rainfall has a great importance on the distribution and the density of molluscs. As a fact, the quantity of water and the drying out period of these ponds depend upon rain factors which rule the existence and the survival of the malacological fauna. In the second part of the rainy season, the population reaches its maximum, i.e., during the reproduction period. Monthly observations show that the relative abundance of B. umbilicatus is higher than that of B. senegalensis. These ponds are dry during 6 to 8 months per year. However the populations of molluscs regenerate regularly, a fact which presupposes a certain ability to resist drought. Some come through this period successfully, but the middle-sized ones (7 to 9.9 mm) resist better than others (70 to 80 per cent of the population). Immediately after the first rains they resume their activity and lay intensively in order to reconstitute the population. B. umbilicatus and B. senegalensis are potential intermediate hosts for human and animal trematode infections, but in the studied region only B. umbilicatus intervenes in the transmission of S. haematobium and S. curassoni which occurs between September and November. Under natural Sahel conditions the epidemiological cycle is short and everything happens within 4 to 6 months with the regeneration and the growth of the population of molluscs, its infestation and the transmission of trematode infections. The ecological behaviour of these molluscs in the North-Sudan region is very important in the epidemiology of human and animal trematode infections and requires a new controlling strategy. The destruction of molluscs is more effective and more economic at the end of the rain season, which is the beginning of the drying of ponds, a period in which they concentrate in the residual water pools.

Animals↗