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At least 73 records · Page 4Linked to original sources

PubMed2005

Trematodes in snails near raccoon latrines suggest a final host role for this mammal in California salt marshes.

Of the 18 trematode species that use the horn snail, Cerithidea californica, as a first intermediate host, 6 have the potential to use raccoons as a final host. The presence of raccoon latrines in Carpinteria Salt Marsh, California, allowed us to investigate associations between raccoons and trematodes in snails. Two trematode species, Probolocoryphe uca and Stictodora hancocki, occurred at higher prevalences in snails near raccoon latrines than in snails away from latrines, suggesting that raccoons may serve as final hosts for these species. Fecal remains indicated that raccoons fed on shore crabs, the second intermediate host for P. uca, and fish, the second intermediate host for S. hancocki. The increase in raccoon populations in the suburban areas surrounding west coast salt marshes could increase their importance as final hosts for trematodes in this system.

Animals↗

PubMed2004

Meningoencephalitis in two stranded California sea lions (Zalophus californianus) caused by aberrant trematode migration.

Meningoencephalitis caused by aberrant trematode migration is described in two California sea lions (Zalophus californianus) admitted to a rehabilitation hospital between May and August 2001. Both animals displayed seizure activity and were euthanized due to poor response to therapy. Gross abnormal findings included liver flukes (Zalophotrema hepaticum) in the bile ducts and areas of swelling and necrosis in the cerebrum, cerebellum, and brain stem. Histopathology revealed meningoencephalitis with necrosis, hemorrhage, and many trematode eggs within the brain. In one sea lion, an adult trematode was found on the surface of the cerebrum. These are believed to be the first reported cases of meningoencephalitis caused by aberrant trematode migration in pinnipeds.

Animals↗

PubMed2000

Temporal variations in the infection of a population of Cerithidea cingulata by larval trematodes in Kuwait Bay.

The prosobranch gastropod Cerithidea cingulata (Gastropoda: Potamididae) in Kuwait Bay was examined for larval trematode infections over a 17-month period. A total of 2537 snails were examined and 1265 (49.9%) found to be infected with one or more species of trematodes. The component community in the snail comprised 12 species representing the families Cyathocotylidae (2), Echinostomatidae (2), Haplosplanchnidae (1), Heterophyidae (2), Microphallidae (1), Philophthalmidae (2), Plagiorchiidae (1) and Schistosomatidae (1). Cyathocotylid II (41.6%) was by far the most prevalent species followed by the microphallid (3.9%), the two species comprised 90% of the total trematode fauna. The prevalence of infection increased with shell size and was significantly higher in male (47%) than female (33%) snails. Multiple infections were observed in only 15 (1.2%) of the infected snails; cyathocotylid I and cyathocotylid II combination occurred 14 times and heterophyid I and the microphallid occurred once. Trematode species were more diverse and prevalent in winter, and cercarial shedding peaked in summer. Behaviour of the definitive host and snail population dynamics were probably the major contributors to the detected temporal pattern in the infections.

Animals↗

PubMedDate not supplied

[The state of knowledge of the class of trematodes and the chief problems in studying them].

The paper deals with the current state of knowledge of Trematoda, trends and aims of further investigations. Up to now the classification system of trematodes has been unsatisfactory though for several large groups it is elaborated with due regard to the biology and ecology of these worms. The main deficiency of the present-day taxonomy of trematodes consists in the existence of two separate classifications, for adult worms and for their larvae (cercariae). Among the existing systems the classification suggested by Odening (1960-1963) is of the greatest interest. We do not agree with his division of the class into three subclasses (including Aspidogastrea) and Diginea into two subclasses, "Sporocystoinei" and "Redioinei", but follow the composition of orders established by him. Great difficulties arise in establishing the characters, taxonomic criteria of trematodes. However, a number of characters can be suggested for differentiation of species and genera at various developmental stages. Deficiency in the taxonomy of these worms is due to a wrong evaluation of their characters and to the lack of common collection and treatment techniques. On describing species one should proceed, if possible, from the whole complex of morphological and biological peculiarities of different ontogenetic stages of the forms under study. A study of the ultrafine structure, hysto- and biochemistry of trematodes will enable us to associate better the morphology and the function of organs and to go deeper into the functional morphology and functional biochemistry. The main task of further investigations is closely connected with the elaboration of a natural system of Trematoda, a study of diverse and deep interrelations in the "parasite-host" system and with the development of scientific methods of control of pathogenic species on the biological basis.

Animals↗

PubMed1988

Application of biotechnology methods to the study of trematodes.

Advances in biotechnology over the past decade offer renewed hope for solutions to trematode parasitoses in Thailand. Trematode diseases have remained the same, but the tools (1) to exploit the innate ability of cells to replicate and produce biological products upon demand, (2) to manipulate the genetic makeup of an organism, (3) and to biologically or synthetically manufacture peptides have provided scientists with new reagents for diagnosing, treating, preventing and controlling trematode diseases. Although recent applications have been focused on schistosomiasis, they have potential application to other trematode diseases (paragonimiasis, clonorchiasis, opisthorchiasis, fasciolopsiasis, and fascioliasis) endemic to Thailand. The optimism which new technology has generated must be tempered with realism and continued support for basic parasitology. Progress is dependent on a combination of approaches involving techniques at the molecular, cellular, organism and population levels. The new tools must be used in conjunction with old knowledge. Most of all there must be a rational strategy for the use of products of new technology. Defined vaccines alone will not be the answer, even if they become a reality. They must be applied in a manner that optimizes their effectiveness. The silver bullets may be out there, but they are still in a roughly molded stage. They must be finished, loaded in an appropriate epidemiological gun, and fired by an expert at specific targets.

Animals↗

PubMed1987

Immunological aspects of snail-trematode interactions.

After penetration into its snail host the trematode not only has to find a suitable environment, it also has to circumvent the activities of its host's internal defence system to survive and to develop normally. Immunological compatibility of snails and trematodes is dependent on the capability of the parasite to evade and/or suppress the defence activities of its host. The possible role of physicochemical properties of the surfaces of the parasite and the host defence cells in evasion of host responses remains unknown; a role is indicated for molecular mimicry in the miracidium and the young mother sporocyst and for masking in the cercaria. Strong evidence exists that trematodes secrete substances which suppress anti-trematode activities of snail haemocytes.

Animals↗

PubMed1984

Socio-economic and cultural aspects of human trematode infections in Korea.

Liver, lung and intestinal trematode infections in Korea are a public health problem, as 3 to 4 million individuals appear to be infected. Corresponding with recently developed and established strategies to control the major endemic trematode infections, also a country specific national control project in Korea is being considered. It concerns the three human trematode infections prevalent in this country, namely clonorchiasis, paragonimiasis and metagonimiasis. In addition to chemotherapy, approaches based on local conditions may be included in such strategies in order to achieve the best possible results. The present paper tries to identify the human socio-economic and cultural factors traditionally involved in the transmission of these trematode infections in Korea. It also describes the changes of patterns of agricultural practices and general environmental modifications that have been achieved by the socio-economic development even in rural communities as concerns the transmission of these parasitic infections. Based on these behavioural and environmental factors, the prevalence of these infections decreased even without any application of mass chemotherapy. Consequently, it can be expected that further health educational and mass chemotherapy programmes will drastically reduce transmission. Cooperation of communities involved will certainly contribute to making control measures a success.

Agriculture↗

PubMed1997

Fish- and shellfish--borne trematode infections in Canada.

Food-borne trematode infections are endemic in various parts of the world, particularly Southeast Asia. Despite the high prevalence, morbidity and total costs of these infections, they remain poorly recognized by public health authorities and consumers. Factors such as poor sanitation and traditional methods of food preparation hasten the spread of food-borne trematode infections in endemic regions and must be carefully examined in order to develop effective control strategies. There is also a growing risk to consumers in non-endemic countries as a result of international trade. A considerable quantity of freshwater fish and shellfish is imported into Canada from endemic countries in Southeast Asia. Some of these products are imported fresh or processed in such a way that the infective metacercariae may not be destroyed. Further, current inspection procedures in Canada may not detect the presence of all parasites in imported fish products. Therefore, there may be a risk of infection if the fish or shellfish is consumed raw or lightly cooked. Many of the cases of infection in Canada involve recent immigrants from endemic regions who have become infected either before arriving or through the consumption of traditional or ethnic dishes prepared from imported products. International travel and the increasing availability and interest in ethnic foods also contribute to the risk of infection in all Canadians. In addition to these imported trematodes, a number of species are found in freshwater fishes and shellfish in North America and have also caused illness in humans. Although the prevalence of infection remains relatively low in Canada, the need for an increased general awareness of food-borne trematode infections and their causes is indicated.

Animals↗

PubMed1998

Influence of trematode parasitism on the growth of a bivalve host in the field.

Trematode-induced gigantism of molluscs, enhanced growth of trematode-parasitised individuals, has been observed in many laboratory studies. This study reports the effect of the sterilising trematode, Rhipidicotyle fennica, on the growth of the freshwater clam Anodonta piscinalis under field conditions. In addition to single infections (prevalence 44%), a few clams (3%) were infected with both R. fennica and Rhipidicotyle campanula. Parasite-induced gigantism was not found; parasites lowered host growth. The decreased in growth was correlated with the quantity of parasite material. Clams with double infections grew the least, although they did not differ significantly from hosts with a heavy single species infection. The growth of the experimental clams was lower than that of undisturbed control clams. Trematode-induced gigantism of molluscs in the field, in general, remains undemonstrated.

Animals↗

PubMed1993

Comparative spectral, electrophoretic and isoelectric properties of trematode haemoglobins.

A comparative study of the spectral, electrophoretic and isoelectric properties of the haemoglobins of three trematodes, Paramphistomum epiclitum, Gigantocotyle explanatum and Gastrothylax crumenifer was carried out. A high absorption in the beta band region indicates that trematode haemoglobins have high oxygen affinities. Electrophoretic mobilities of all trematode and their host haemoglobins were different. The isoelectric points of trematode haemoglobins were found to focus in the acidic range except that of G. crumenifer haemoglobin I, which focused at an alkaline pH.

Animals↗

PubMed1976

Spectrophotometric analysis of haemoglobins of some digenetic trematodes and their hosts.

The haemoglobins of six different species of trematodes: Gastrothylax crumenifer, Srivastavaia indica, Gigantocotyle explanatum, Fasciolopsis buski, Gastrodiscoides hominis, Isoparorchis hypselobagri and their three different hosts: Bubalus bubalis, Sus scrofa, and Wallago attu were spectrophotometrically investigated, and were found to contain porphyrin IX as the common prosthetic group. Oxyhaemoglobin, carbonmonoxy-haemoglobin and reduced haemoglobin of all 6 species of trematodes and their 3 hosts under study gave similar absorption maxima. Distinct differences were, however, observed in the nature of the spectral curves of cyanmethaemoglobin which exhibit 2 absorption maxima in the beta and the alpha region in the case of all trematodes whereas in the case of similar host haemoglobin derivatives only one single broad peak in the 536-540 nm region was obtained. With respect to pyridine derivatives all the trematode haemoglobins show a sharp peak in the alpha region and a minor hump in the beta region except Gastrothylax crumenifer. All three host pyridine haemoglobin derivatives show only a single broad peak at 570 nm.

Animals↗

PubMed2004

A cathepsin F of adult Clonorchis sinensis and its phylogenetic conservation in trematodes.

A novel 28 kDa cysteine protease (Cs28CF) secreted by the hepatobiliary trematode, Clonorchis sinensis was identified. The protease was purified from the excretory-secretory products (ESP) of the adult worm using DEAE-ion exchange and Arginine-Sepharose 4B chromatography. It showed a high activity between pH 6.5 and 7.5 in a dithiothreitol (DTT)-dependent manner. Inhibitors specific to cysteine proteases down-regulated the activity. Addition of Cs28CF to monkey cholangiocyte cultures resulted in approximately 95% cell death after 7 days. The full-length cDNA (1078 bp) encoded a single peptide of 328 amino acids (aa) with an N-terminal hydrophobic sequence, an ERFNAQ motif in the propeptide and a mature domain. Expression of mRNA transcripts of Cs28CF was observed in both the metacercaria and adult stages. Bacterially expressed recombinant protein exhibited a specific antibody reaction with clonorchiasis sera. Deduced aa exhibited 52-76% sequence identity with the cathepsin F analogues from other organisms. A novel E/DXGTA motif was recognized in the propeptide region. Phylogenetic analysis of 63 papain family members revealed that the trematode cysteine proteases formed 2 major clades of cathepsins F and L. The trematode cysteine proteases classified as cathepsin F shared higher homology among themselves than those classified as cathepsin L. Cathepsin F is phylogenetically conserved in the trematode parasites as well as in mammals.

Amino Acid Motifs↗

PubMed2005

Signal transduction in larval trematodes: putative systems associated with regulating larval motility and behaviour.

The multi-host lifestyle of parasitic trematodes necessitates their ability to communicate with their external environment in order to invade and navigate within their hosts' internal environment. Through recent EST and genome sequencing efforts, it has become clear that members of the Trematoda possess many of the elaborate signal transduction systems that have been delineated in other invertebrate model systems like Drosophila melanogaster and Caenorhabditis elegans. Gene homologues representing several well-described signal receptor families including receptor tyrosine kinases, receptor serine tyrosine kinases, G protein-coupled receptors and elements of their downstream signalling systems have been identified in larval trematodes. A majority of this work has focused on the blood flukes, Schistosoma spp. and therefore represents a narrow sampling of the diverse digenean helminth taxon. Despite this fact and given the substantial evidence supporting the existence of such signalling systems, the question then becomes, how are these systems employed by larval trematodes to aid them in interpreting signals received from their immediate environment to initiate appropriate responses in cells and tissues comprising the developing parasite stages? High-throughput, genome-wide analysis tools now allow us to begin to functionally characterize genes differentially expressed throughout the development of trematode larvae. Investigation of the systems used by these parasites to receive and transduce external signals may facilitate the creation of technologies for achieving control of intramolluscan schistosome infections and also continue to yield valuable insights into the basic mechanisms regulating motility and behaviour in this important group of helminths.

Animals↗

PubMed2003

Egg size variability in trematodes: test of the bet-hedging hypothesis.

The hypothesis according to which egg size variability in hermaphroditic parasites results from bet-hedging was investigated in a comparative analysis using trematodes as a model. We hypothesized that the species reproducing mainly by self-fertilization should produce smaller eggs than those species that regularly practice cross-fertilization. Indeed, because self-fertilization is usually associated with inbreeding depression, selection should favor individuals spreading the risk of genetically disturbed development across more but smaller eggs, instead of producing fewer eggs, each possessing a large resource supply, of which many may fail to develop because of genetic deficiencies. On the basis of earlier theoretical and empirical studies, we assumed that the ratio length of testis-length of ovary positively correlates with the mating group size and, hence, with opportunities for cross-fertilization. In accordance with the bet-hedging hypothesis, we found, across trematode species, a positive relationship between this ratio and the mean egg volume produced by adults. This result was, however, observed only for the trematodes infecting birds and not for the species infecting fishes and mammals. In addition, once the influence of trematode phylogeny was taken into account, there was no significant trend, suggesting that phylogenetic legacies played a large role in generating the previous signal. Experimental tests of the bet-hedging hypothesis will be necessary to clarify the matter.

Animals↗

PubMed1980

Seasonal variation of snail population of Parafossarulus manchouricus and larval trematode infection in river Kumho, Kyungpook province, Korea.

Studies were conducted to determine the ecology of the snail, Parafossarulus manchouricus, the seasonal variation of the snail population, and the infestation rates of these snails with the cercariae of digenetic trematodes, in the snail habitat of river Kumho, in Dongchon of Taegu city, in Kyungpook Province, Korea, from 1975 to 1979. The earliest time the snails were found was early in April every year. At that time the water temperature ranged from 13 to 14 degrees C. The population density of snails ranged from 2 to 8 per square meter. The highest population density of snails was encountered in late June and the water temperature was between 24 and 26 degrees C. The snails disappeared in early and mid-November, when the water temperature dropped to 10~13 degrees C. The average snail population in June was 115.9 per square meter in 1975 but in 1976 dropped abruptly to 30.5 and remained at approximately the same level in 1977. It then decreased at considerably lower rates, with the average of 18.7 in 1978 and 14.5 in 1979. The snails collected in the habitat were examined for the presence of cercariae of digenetic trematodes. Of these, four species, Clonorchis sinensis, Cyathocotyle orientalis, Exorchis oviformis, and Loxogenes liberum were found. The most frequently liberated cercaria was L. liberum 43.3 per cent, followed by E. oviformis 6.2 per cent and C. orientalis 1.5 per cent. The least frequently liberated was C. sinensis 0.1 per cent. In the monthly liberation rates for larval trematodes, the higher rates were observed in June, July and August every year, and the cercarial rates for Clonorchis sinensis, Cyathocotyle orientails and Exorchis oviformis demonstrate a fairly consistently fluctuating downward trend over the five-year period, except for Loxogenes liberum. Summarizing the results, this study indicated that the population density of snails in the habitat and the infection of the snail with the cercariae of digenetic trematodes has decreased over the five-year period from 1975 to 1979.

Journal Article↗

PubMed1981

Studies On Parasitic Helminths Of Korea 5.Survey On Intestinal Trematodes Of House Rats.

A study was carried out to evaluate the house rats in southern Korea as reservoir host of intestinal trematodes, in 13 different areas: 7 in inland and 6 in brackish-water zones, during the period from August 1980 to August 1981. A total of 170 house rats was captured; 101 rats from inland and 69 from brackish-water zones. They consisted of 129 Rattus norvegicus, 22 R. rattus rufescens, and 19 unidentified. The infection status of the rats were as follows: 1. Total 29 rats (17.1%) were infected by one or more kinds of intestinal trematodes; 27 from inland and 2 from brackish-water zones by areas. Rats in inland were more heavily infected. 2. The intestinal trematodes collected from rats were identified as Echinostoma hortense, E. cinetorchis, Plagiorchis muris, Fibricola seoulensis, Clonorchis sinensis and Metagonimus yokogawai. 3. As a reservoir host, the rats were very important in Echinostoma hortense and E. cinetorchis infection. Rats infected with these trematodes were found widely in southern Korea, and its infection rates were the highest among the discriminated flukes. 4. In this study, no rats were found to be infected with Heterophyes and Pygidiopsis even in endemic areas. The negligible importance of rats as reservoir host of these heterophyid should be reevaluated in the future.

Journal Article↗

PubMed1981

Infestation With Larval Trematodes From Fresh-Water Fish In Natural And Fish Breeding Ponds.

The present study was undertaken to determine the pattern of infestation with the encysted larvae of digenetic trematodes in freshwater fish collected in both the natural and fish breeding ponds in Kyungpook Province, Korea. The fish collected in the two natural ponds, Nass-chil, and Sa-il, and three fish breeding ponds, Deok-dong, Mo-gok, and Seongryu-tunnel, were examined from July 1980 to August 1981. The data were compared with the results obtained from freshwater fish caught in the river Kumho by Hwang and Choi(1980). Ten species of fish caught in the ponds were examined for the presence of the larval trematodes. Seven species of the larvae, Clonorchis sinensis, Cyathocotyle orientalis, Echinochasmus species, Exorchis oviformis, Metacercaria hasegawai, Metagonimus yokogawai, and Metorchis orientails and two kinds of undetermined cyst A and B were found. The infestitation rate for Clonorchis sinensis metacercaria in the Korean shiner, Gnathopogon atromaculatus collected in the natural ponds was higher than the rate in the river Kumho by Hwang and Choi(1980), but lower in the fish collected in the breeding ponds. By contrast, the infestation rate in the flat bitterling, Paracheilognathus rhombea in ponds was higher, while there was no change of the rate in the southern top-mouthed minnow, Pseudorasbora parva. The intensity of infestation, expressed as the average number of Clonorchis sinensis metacercaria per gram of flesh, were lower than in the bullhead, Coreobagrus brevicorpus, and Gnathopogon atromaculatus in the ponds in 1981. The intensity was higher in Paracheilognathus rhombea, but no fluctuation in the intensity of infestation in Pseudorasbora parva was observed. The infestation rates and densities for the encysted larvae of digenetic trematodes except for Clonorchis sinensis varied from fish to fish. However, it was found that the rate and intensity of the larval trematodes from all the fish in the ponds was lower than from those in the rivers in Kyungpook Province, Korea.

Journal Article↗

PubMed1983

[Survey On Encysted Cercariae Of Trematodes From Fresh-Water Fishes In Mangyeong Riverside Area]

In order to clarify infestation pattern for the encysted larvae of digenetic trematodes from fresh-water fishes, this survey was carried out from March to September, 1983. A total of 380 fishes of 32 species were collected with netting at the three reaches, upper, middle and lower in Mangyeong riverside area. After the fishes were dissected into small scraps, they were pressed under cover glass and examined for the presence of those of digenetic trematodes with a microscope. The results obtained were as follows: Out of a total of 380 fishes inspected, 320 fishes (84 %) from 31 species were found positive with digenetic trematode metacercariae; more than 10 species of the metacercariae were detected in Pseudorasbora parva; Gnathopogon majimae, Microphysogobio yaluensis, Cultriculus eigenmanni and Gnathopogon coreanus (more than 8 species); Aphyocypris chinensis(8 species) and etc. respectively. Clonorchis sinensis metacercariae were found positive from 93 fishes (25 %) from 12 species detection rates in other species of digenetic trematode metacercariae from various fishes were; Exorchis oviformis, 261 fishes (57 %) from 28 species; Cyathocotyle orientalis, 47 fishes (12 %) from 12 species; Metorchis orientalis, 21 fishes (6 %) from 12 species; Metagonimus yokogawai, 164 fishes (43 %) from 26 species; Pseudexorchis major, 71 fishes (19 %) from 18 species; Metacercaria hasegawai, 77 fishes (20 %) from 25 species; Centrocestus armatus, 24 fishes (6 %) from 7 species; Echinochasmus japonicus, 2 fishes (0.5 %) from 2 species, and unidentified species, 34 fishes (9 %) from 15 species respectively. The sums of average number of the encysted larvae of all species found in fish body/gram showed 83 in P. parva, Cobitis taenia (74.2), A. chinensis (28.5), Pseudoperilampus uyekii (26.6), G. majimae (19.6) and etc. respectively and the average peak number of each metacercaria in fish body/gram showed 21.7 C. sinensis, 24 E. oviformis, 15.3 M. orientalis and 6.1 E. japonicus in P. parva; 42.7 C. orientalis and 25.1 M. yokogawai in C. taenia; 8.3 C. armatus and 8.3 M. hasegawai in P. uyekii; 6.3 P. major in Carassius carassius, and 2.9 unidentified species in G. majimae respectively.

Journal Article↗