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PubMedDate not supplied

[An analysis of the results of clinical trials of praziquantel analogs in intestinal cestode and trematode infections. 2. The treatment of liver trematode infections (opisthorchiasis, fascioliasis) and schistosomiasis].

The authors did not detect any differences in the efficacies and tolerance of praziquantel analogs manufactured by various firms (azinox, Russia; pikitor, China; cesol, cisticide, biltricide, Bayer, Merk, Germany, India). These drugs were found highly effective in opisthorchiasis (87.8%) and schistosomiasis (91.7%) and ineffective in fascioliasis. The efficacy and tolerance of azinox, a drug manufactured in this country, was similar to those of its foreign analogs.

Adolescent↗
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↗
PubMed1991

Hemocyte production in trematode-infected Lymnaea truncatula.

In trematode-infected Lymnaea truncatula, as in other lymnaeids, hemocytes are formed in the connective tissue. Mitoses are found singly in blood vessels or connective tissue or occur in hemocyte nodules, developing along the mantle epithelium or associated with blood sinuses. The so-called hemocyte-producing organ in L. truncatula is not equivalent to that in Biomphalaria glabrata, but rather involves the proximal part of the kidney sac. It has a dual structure: the main part, containing podocytes and broad hemal spaces, is adapted for hemolymph filtration; the apical portion, adhering to the mantle and pericardial epithelia, has a thicker connective-tissue frame in which hemocyte nodules may develop. The role of this region of the kidney in hemocyte formation is discussed.

Animals↗
PubMed2002

Synergism between trematode infection and pesticide exposure: a link to amphibian limb deformities in nature?

The apparently rapid increase in the prevalence of amphibian limb deformities has led to substantial interest from ecologists and public health professionals. Hypotheses proposed to explain the deformities fall into two broad categories: chemical contaminants and trematode infection. Although there are convincing experimental demonstrations that certain factors can lead to some deformities, the causes for recent increases in amphibian malformation remain controversial. Moreover, no experimental studies on amphibian deformities have been conducted in the field, and no studies have attempted to examine the synergistic effects of trematode infection and exposure to chemical contaminants. Here, I present the results of field and laboratory experiments that link increased trematode infection, and increased limb deformities, to pesticide exposure. Field experiments conclusively demonstrated that exposure to trematode infection was required for the development of limb deformities in wood frogs, Rana sylvatica. However, deformities were more common at sites adjacent to agricultural runoff. Laboratory experiments corroborated the association between pesticide exposure and increased infection with pesticide-mediated immunocompetency as the apparent mechanism. Given the conservative contaminant exposure levels used [Environmental Protection Agency (EPA) drinking water standards] and the widespread use of many pesticides, these negative impacts may help to explain pathogen-mediated amphibian declines in many regions.

Amphibians↗
PubMedDate not supplied

Intestinal trematode infection in North Bihar.

Reports of intestinal trematode infections are not common from Bihar, India. However, we herewith report one case of fasciolopsiasis from North Bihar, India. A 14 years old girl presented with diarrhea, vomiting, generalized pain abdomen and loss of weight. Routine stool examination and upper gastrointestinal endoscopy revealed fasciolopsis buski in large numbers. Her rural life style and food habit (ingestion of raw vegetables- caltrops and water chest nuts) supported the cause of infestation. Despite treatment with praziquantel, the patient died after two days. Mild infestations of Fasciolopsis buski may pass on unnoticed. However, heavy infestations may cause considerable prostration, illness and even death in younger age groups. Awareness regarding this parasitic infestation (endemic in some regions), especially in the rural set up is still a much needed entity.

Adolescent↗
PubMedDate not supplied

[Effect of different concentrations of heavy metal ions on the normal physical and chemical characteristics of the hemolymph of Palanorbarius purpura (Mollusca: Bulinidae) in the norm and during a trematode infection].

Short-term simultaneous effect of high concentrations (LC25, LC50, LC75) of heavy metal ions. (Cu2+, Zn2+, Cd2+ and Pb2+) and infection with trematode partenites Echinoparyphium aconiatum onto haemolymph of mollusk has been investigated. It was noted that low doses of toxicant (2.5 and 10 maximum admitted concentrations) have variable effect. In infected molluscs the concentration of haemoglobin decreases, while in intact ones it increases. In relation to this index, it was found, that the ion Cu2+ is highly toxic, Zn2+ and Cd(2+)--toxic, Pb(2+)--moderately toxic.

Animals↗
PubMed2001

Trematode infection and the distribution and dynamics of parthenogenetic snail populations.

According to the Red Queen hypothesis for sex, cross-fertilization should be positively associated with the probability of exposure (risk) to virulent parasites. Unfortunately, risk is difficult to measure in the wild, and prevalence of infection is often substituted for risk. Here I suggest that prevalence of infection may not generally suffice as a surrogate for risk, since the Red Queen model can make opposite predictions depending on the distribution of risk in the wild. Specifically, the results of a matching-alleles model suggest that asexual populations should be more infected than sexual populations, when (1) the variance in risk among populations is small, and (2) the mean risk of exposure to parasites is near the point where selection switches to favouring sex over asex. If, however, the variance in risk among populations is large, sexual reproduction should be positively associated with the prevalence of infection. In addition, the coefficient of variation for reproductive mode should increase sharply at the switch point. In light of these results, I re-evaluated data from two studies on the distribution of males in 95 populations of a freshwater snail (Potamopyrgus antipodarum). Populations of these snails are often mixtures of sexual and asexual individuals, and the frequency of males is correlated with the frequency of sexual females in the population. The results show a large, highly skewed variance among populations for prevalence of infection by larval trematodes. The results also show a positive, significant relationship between prevalence of infection and the frequency of males, with a sharp increase in the coefficient of variation at intermediate prevalence. In addition, experimental studies suggest that some of the necessary conditions of the Red Queen hypothesis are also met in this system. Specifically, the most common trematode infecting these snails is (1) adapted to infecting local host populations of the snail, and is (2) more infective to clones that were common in the recent past. It is too early to knoxv if the parasite theory is sufficient to explain the widespread distribution of sex. I suggest that the theory is not sufficient, but that parasites in combination with mutation accumulation in clonal lines may explain the maintenance of sex in species that occasionally produce apomictic mutants.

Animals↗
PubMed2006

Road facilitation of trematode infections in snails of northern Alaska.

Road disturbances can influence wildlife health by spreading disease agents and hosts or by generating environmental conditions that sustain these agent and host populations. I evaluated field patterns of trematode infections in snails inhabiting ponds at varying distances from the Dalton Highway, a wilderness road that intersects northern Alaska. I also assessed the relationships between trematode infections and snail densities and six environmental variables: calcium concentration, aquatic vegetative cover canopy cover temperature, pond size, and community structure. Presence of trematode infections and snail density were negatively correlated with distance from the highway. Of the pond characteristics measured, only calcium concentration and vegetation density declined with distance from road. However neither variable was positively associated with snail density or trematode presence. One potential explanation for observed patterns is that vehicles, road maintenance, or vertebrate vectors attracted to the highway facilitate colonization of snails or trematodes. Emerging disease threats to biological diversity in northern ecosystems highlight the importance of understanding how roads affect disease transmission.

Alaska↗
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↗
PubMed1998

Larval trematode infections in freshwater gastropods from the Albufera Natural Park in Spain.

Malacological samplings were made from January 1994 to December 1996 in the Albufera Natural Park (Valencia, Spain) to trace the dynamics of molluscan populations and the prevalence and intensity of infection by larval trematodes. A total of 10,533 freshwater gastropods belonging to seven species (Lymnaea auricularia, L. truncatula, L. palustris, L. peregra, Bithynia tentaculata, Physa acuta and Gyraulus chinensis) was examined, and 110 (1.04%) were found to harbour some of the nine distinguishable types of cercariae, namely four echinostome cercariae (Hypoderaeum conoideum, Echinoparyphium recurvatum, Euparyphium albuferensis, and Echinostoma sp.), four furcocercous cercariae, and one xiphidiocercous cercaria. This study shows that the composition of the snail and trematode communities may be determined by the particular environmental conditions present and the human intervention in the area.

Animals↗
PubMed2004

Factors influencing the distribution of digenetic trematode infections in a mudsnail (Hydrobia ventrosa) population inhabiting salt marsh ponds in Iceland.

This study analyzed the influence of several abiotic and biotic variables on the distribution of digenetic trematode infections in a mudsnail, Hydrobia ventrosa, population inhabiting 12 ponds on the Melabakkar salt marsh in Iceland, the northwestern limits of the geographical distribution. Nine trematode species were found to infect the snail population, which included Microphallus pirum, Microphallus breviatus, Microphallus claviformis, Maritrema subdolum (Microphallidae), Cercaria Notocotylidae sp. 11 Deblock, 1980, C. Notocotylidae sp. 12 Deblock, 1980, C. Notocotylidae sp. 13 Deblock, 1980 (Notocotylidae), Cryptocotyle concavum (Heterophyidae), and Psilostomum brevicolle (Psilostomatidae). Correlations between biotic variables (snail density in the ponds and vegetation cover), abiotic variables (distance of each pond from the sea, pond elevation above chart datum, size, average depth, salinity, and some characters of the littoral zone and sediments), and trematode infections were analyzed. These variables indirectly affected the trematode infections because some determined how attractive the ponds were for the final hosts, which were various species of marine and shore birds. We propose that their habitat use and defecating habits are the main determinants of the trematode distribution in the area.

Animals↗
PubMed1984

Changing patterns of some trematode infections in Asia.

In certain areas of Asia the pattern of trematode infections in both man and animals seems to have changed in the recent past. On Taiwan, for example, paragonimiasis, fasciolopsiasis and schistosomiasis were at one time highly endemic in certain locations, but in recent years these parasitoses have been difficult to find in definitive, intermediate as well as reservoir hosts. Education, industrialization, alterations in the ecology and the use of modern agricultural practices have contributed to the changes. Conversely, it appears that human clonorchiasis is increasing in Taiwan while in Hong Kong, the disease, once highly prevalent, seems to be decreasing due to control measures implemented in China; the source of infected fish for Hong Kong residents has been China. Furthermore, Clonorchis sinensis infections are more common in higher income groups of Hong Kong since imported fish are more expensive. Along the same line, metagonimiasis is more common among the more affluent sports fishermen in Japan who eat mountain-stream trout as "sashimi" soon after the catch. One of the most dramatic changes in the prevalence of a trematode disease has been in the Lindu Lake region of Central Sulawesi, Indonesia. Echinostomiasis lindoensis was highly endemic in the area and human infection was acquired by eating infected Corbicular sp. clams. The fish Tilapia mossambica was subsequently introduced into the lake and competed for food with the clam and ate the glochidial larval stages of the clam. The clams are no longer present in the lake and consequently, the parasitosis has disappeared.(ABSTRACT TRUNCATED AT 250 WORDS)

Asia↗
PubMed1982

Trematode infections in Pirenella conica in three sites of a mangrove lagoon in Sinai.

Over a period of 11 months, eight samples of Pirenella conica were taken at each of three sites of a mangrove lagoon in Sinai. Infection with larval trematodes, especially of Heterophyidae, was highest at the site within the mangrove thicket with a breeding colony of reef herons, the supposed definitive hosts of the Heterophyidae. The lowest frequency of infection was recorded from a tide-pool on the broad sand-flats surrounding the lagoon, where there was a great variation in the abundance of snails and xiphidiocercariae were more common than heterophyid cercariae. Predation from fish or other molluscs did not appear to be an important factor at either of these two sites. In all three sites, double infections of Heterophyidae and trematodes with xiphidiocercariae as well as of Heterophyidae and Echinostomatidae occurred less frequently than theoretically expected, but there was no competitive exclusion between Echinostomatidae and xiphidiocercariae.

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↗