A simplified method to estimate Diphyllobothrium spp. infection in salmonids.

Some fish parasites constitute severe management problems as they may cause mortality of their fish host or are important zoonoses of humans. Parasite assessments are therefore critical to keep track of infections. If conventional sampling techniques can be simplified, parasite assessments might be easier to obtain, less time-consuming and more extensive. In this study, we compare the assessed number of Diphyllobothrium spp. cysts (CYST) with the counted number of Diphyllobothrium spp. plerocercoid larvae recovered using a conventional digestive technique (LARV). The aim was to determine the potential of using CYST as a simplified methodology for assessing Diphyllobothrium spp. infection in salmonids. In total, 365 brown trout and 424 Arctic charr were sampled from nine lakes in subarctic Norway. Strong correlation, significant linear relationship and large amount of explained variation were found between log10 CYST and log10 LARV in both fish species. The method had a slight, but not significant tendency to work better in charr compared to trout. In addition, absolute difference between CYST and LARV increased at parasite intensities >100 indicating that the method has reduced functionality when estimating parasite intensity in heavily infected salmonid populations. However, overall, using this simplified and less time-consuming methodology, a good indication of Diphyllobothrium spp. intensity, abundance and prevalence was obtained. We suggest that this method provides a sound proxy of the Diphyllobothrium spp. burden and have the potential to be used in parasite assessment during fish monitoring and fisheries management surveys, particularly if the time and resources for detailed parasite studies are not available.

Diphyllobothrium dendriticum (Cestoda: Diphyllobothriidae) in the Intestinal Tract of the Herring Gull Larus argentatus: Localization and Trophic Parameters.

We studied the activities both of digestive enzymes in the small intestine of the herring gull (Larus argentatus) and a tapeworm Diphyllobothrium dendriticum (Cestoda: Diphyllobothriidae) residing in the intestine. It was found that D. dendriticum infects the medial section of the small intestine of the herring gull. Such localization of D. dendriticum is caused by the maximal activity of proteases and glycosidases and by the high rate of membrane and cavitary digestion in this section. The activity of protease and glycosidase in gulls infected with D. dendriticum is decreased. The activity of proteases in the fractions desorbed from the tegument surface of D. dendriticum is significantly higher than that of glycosidases.

Pacific Broad Tapeworm Adenocephalus pacificus as a Causative Agent of Globally Reemerging Diphyllobothriosis.

The Pacific broad tapeworm Adenocephalus pacificus (syn. Diphyllobothrium pacificum) is the causative agent of the third most common fish-borne cestodosis among humans. Although most of the nearly 1,000 cases among humans have been reported in South America (Peru, Chile, and Ecuador), cases recently imported to Europe demonstrate the potential for spread of this tapeworm throughout the world as a result of global trade of fresh or chilled marine fish and travel or migration of humans. We provide a comprehensive survey of human cases of infection with this zoonotic parasite, summarize the history of this re-emerging disease, and identify marine fish species that may serve as a source of human infection when eaten raw or undercooked.

[The specific features of Diphyllobothrium latum circulation in the natural foci of the Kostroma region].

Three hundred pikes in the Kostroma section of the Gorky Reservoir, in the Kostroma Overflow, and in the Galich and Chukloma Lakes were examined for infection with Diphyllobothrium latum larvae. In the Kostroma section of the Gorky Reservoir and in the Kostroma Overflow, diphyllobothriasis was recorded in 66.7% (12/18) and 14.7% (11/75) of the pikes, respectively. The high intensity of the epidemic process in diphyllobothriasis was confirmed in the Kostroma Region. The number of notified cases was noted to tend to increase: 35 and 173 cases in 1994 and 1999, respectively.

Detection and identification of Diphyllobothrium nihonkaiense plerocercoids from wild Pacific salmon (Oncorhynchus spp.) in Japan.

We investigated the risk of diphyllobothriasis from ingestion of wild Pacific salmon in Japan by surveying Diphyllobothrium plerocercoids in 182 salmon samples obtained from Japan. The plerocercoids were not detected in chum salmon (Oncorhynchus keta) (0/26), called Akizake in Japan, caught between September and November. However, the detection rate of plerocercoids in chum salmon, called Tokishirazu in Japan, caught between early April and June, was 51.1% (24/47) with an average of two plerocercoid larvae per fish. The detection rates of cherry salmon (Oncorhynchus masou) and pink salmon (Oncorhynchus gorbuscha) were 12.2% (10/82) and 18.5% (5/27), respectively, and the average number of plerocercoids per fish was 0.45 (37 larvae/82 fishes) and 0.22 larvae (6 larvae/27 fishes), respectively. Plerocercoids isolated from O. keta and O. masou were identified as Diphyllobothrium nihonkaiense on the basis of molecular analysis of the cox1 and nad3 genes. Moreover, four tapeworms (three from O. keta and one from O. masou) were obtained by infecting golden hamsters with plerocercoids. The morphological features of these tapeworms were similar to those of D. nihonkaiense isolated from humans. Therefore, we think that O. keta and not O. masou is the most important source of plerocercoid infections in Japan.

[Morphofunctional characteristics of thymus and immunological parameters in golden hamster under experimental invasion with the cestode Diphyllobothrium dendriticum].

Morphofunctional changes induced by the tapeworm in the thymus and blood of its definitive host, by an example of the experimental model "Diphyllobothrium dendriticum--Mesocricetus auratus", have been investigated. The morphofunctional changes in the thymus and immunological transformations in the organism of infested hamster are evidences of rather high immunogenic effect of the D. dendriticum antigens on the definitive host at the period of active growth of the parasites.

Diphyllobothrium nihonkaiense (Yamane et al., 1986) in Switzerland: first molecular evidence and case reports.

We report the first cases of locally-acquired Diphyllobothrium nihonkaiense (Yamane, Kamo, Bylund and Wikgren, 1986) in Switzerland, confirmed by genetic analysis (18S rRNA, COI and ITS1-5.8S rRNA-ITS2 genes). Diphyllobothriasis in this country is attributed to the tapeworm D. latum (Linnaeus, 1758) but the increasing popularity of raw fish culinary specialities (sushi, carpaccio, tartare) brings out a new diagnostic problem, so that people can get infected by exotic species of tapeworms.

Mathematical algorithm for the automatic recognition of intestinal parasites.

Parasitic infections are generally diagnosed by professionals trained to recognize the morphological characteristics of the eggs in microscopic images of fecal smears. However, this laboratory diagnosis requires medical specialists which are lacking in many of the areas where these infections are most prevalent. In response to this public health issue, we developed a software based on pattern recognition analysis from microscopi digital images of fecal smears, capable of automatically recognizing and diagnosing common human intestinal parasites. To this end, we selected 229, 124, 217, and 229 objects from microscopic images of fecal smears positive for Taenia sp., Trichuris trichiura, Diphyllobothrium latum, and Fasciola hepatica, respectively. Representative photographs were selected by a parasitologist. We then implemented our algorithm in the open source program SCILAB. The algorithm processes the image by first converting to gray-scale, then applies a fourteen step filtering process, and produces a skeletonized and tri-colored image. The features extracted fall into two general categories: geometric characteristics and brightness descriptions. Individual characteristics were quantified and evaluated with a logistic regression to model their ability to correctly identify each parasite separately. Subsequently, all algorithms were evaluated for false positive cross reactivity with the other parasites studied, excepting Taenia sp. which shares very few morphological characteristics with the others. The principal result showed that our algorithm reached sensitivities between 99.10%-100% and specificities between 98.13%- 98.38% to detect each parasite separately. We did not find any cross-positivity in the algorithms for the three parasites evaluated. In conclusion, the results demonstrated the capacity of our computer algorithm to automatically recognize and diagnose Taenia sp., Trichuris trichiura, Diphyllobothrium latum, and Fasciola hepatica with a high sensitivity and specificity.

[Infestation with the tapeworm Diphyllobothrium latum after eating raw fish]. / Infestatie met de lintworm Diphyllobothrium latum na het eten van rauwe vis.

A 31-year-old man with no relevant medical history encountered a white, ribbon-shaped object, 15 cm long and approximately 1 cm wide, in his faeces. It turned out to be Diphyllobothrium latum, a tapeworm that has fish as the intermediate host. The patient had eaten raw fish and shellfish during a holiday in Brazil 5 months before. He recovered after a single dose of praziquantel.

[The history of the exploration of the Diphyllobothrium latum life cycle]. / Historia odkrycia i opisania cyklu rozwojowego Diphyllobothrium latum L.

Diphyllobothrium latum typically occur in the subarctic and temperature zones of the Eurasian Continent, however it is also observed in the Arctic Region and Australia. Raw fish meat and raw shell-fish containing plerocercoids is the main source of human infections. Humans are the principial final host of D. latum. Under primitive conditions human excrements with immature tapeworm eggs are deposited anywhere. After embrionic development which occurs in the water, the eggs are transformed into coracidia. Two intermediate hosts (cyclop and fish) are needed for further development. The free-swimming coracidium must enter the stomach of different species of Copepoda. After contact with the intestinal juice of the cyclop, the coracidium loses its ciliated envelope and the hooks become mobile. The metamorphosis of the oncosphere to the procercoid occurs. The discovery of the procercoid done by Janicki and Rosen in 1917 implied that the missing link in the cycle of the broad tapeworm had been found. The copepod including the procercoid is consumed by the second intermediate host. The larvae escape from the digestive tract of the fish and are transformed into a plerocercoid. The plerocercoids develop slowly in the fish, and they must reach a certain degree of maturity to be capable of infecting the final host. Today the life cycle of the tapeworm is well recognized and well illustrated in parasitological textbooks and websites. In this paper the history of the exploration of the D. latum life cycle is described. Additionally the main scientific researches carried out on life stages of the broad tapeworm have been reviewed.

Evaluation of Modified Formalin-Ether Concentration Method Using Para Tube in Clinical Settings.

Conventional formalin-ether concentration method is a gold standard for the diagnosis of parasite infection. However, it may be time-consuming and laborious. We aimed to reveal the clinical usefulness of a modified formalin-ether concentration method using the Para Tube (KS Corporation, Korea) compared with the conventional method. A total of 117 fresh, unpreserved fecal samples composed to 90 negative controls and 27 positive controls with ova of Diphyllobothrium latum/D. nihonkaiense, ova of Clonorchis sinensis and cysts of Giardia lamblia were used in this study. Both methods showed comparable correct identification rate (87.2% for the Para Tube vs. 86.3% for the conventional method).When five samples were examined at once, the Para Tube method reduced the procedure time compared with the conventional method (19 min 58 sec vs. 23 min 18 sec, P=0.0286). We concluded that the modified formalin-ether concentration method using the Para Tube is a rapid, simple, and reliable fecal concentration method for clinical use.

Three main patterns in the expression of six actin genes in the plerocercoid and adult Diphyllobothrium dendriticum tapeworm (Cestoda).

The expression of six actin genes was examined in adult and plerocercoid Diphyllobothrium dendriticum tapeworms using in situ hybridization. On the basis of their structures, these genes are divided into three groups, the cestoda-I, -II and -III actins. Current studies show that the expression of actins belonging to different groups vary to a great extent. The three cestoda-I actins are expressed primarily in muscle cells of both adult and plerocercoid tapeworms, the expression being restricted to fewer cells in the plerocercoid larva. The two cestoda-II actins are cytoplasmic actin isoforms, expressed in a variety of cells, i.e. in cells dividing, differentiating and migrating. Expression of the cestoda-III actin gene is detected merely in the peripheral part of the outer parenchyma, mainly in the tegument cell bodies. This pattern is very weak in plerocercoids. The results indicate that actins also in D. dendriticum can be divided into cytoplasmic and muscle-specific isoforms. In this organism, one major pattern of muscle actin gene expression (cestoda-I) and two major patterns of non-muscle actin gene expression (cestoda-II and -III) were found.

Leucocyte migration in rainbow trout (Oncorhynchus mykiss [Walbaum]): optimization of migration conditions and responses to host and pathogen (Diphyllobothrium dendriticum [Nitzsch]) derived chemoattractants.

A rainbow trout leucocyte-derived chemoattractant(s) was prepared and tested as a stimulant of leucocyte migration. It was used to optimize an in vitro leucocyte migration assay using a 48-well micro chemotaxis chamber. This assay has subsequently been used to test the chemoattractant activity of antigen extracts from the tegument of Diphyllobothrium dendriticum plerocercoids and conditioned medium obtained after in vitro maintenance of live plerocercoids. Leucocytes were found to have an increased directional motility (chemotactic response) to the host-derived chemoattractant(s) but a random increased motility (chemokinetic response) following stimulation/contact with parasite-derived antigens.

Temperature effects on embryonic development and the life cycle of Diphyllobothrium dendriticum.

Diphyllobothrium dendriticum eggs collected from hamster faeces were incubated at 10 or 20 degrees C, or maintained at 4 degrees C for 11-30 months. On day 65, 20-50% of eggs failed to hatch at 10 degrees C and 42-51% did not hatch by day 21 at 20 degrees C. Our study indicates that eggs begin to hatch in mid-August and persist until October in many lakes within the natural range of D. dendriticum. Our results demonstrate that eggs stored at 4 degrees C will hatch, suggesting they can persist in the environment for long periods and contribute to the D. dendriticum life cycle in high Arctic lakes by hatching months or years after release.

Helminthic food-borne infections.

The importance of food-borne helminthic infections is not well recognized and has not received the same attention as food-borne bacterial infections. Poverty, overpopulation, and cultural practices contribute to conditions that maintain food-borne helminthic infections. The development of better means of transportation and the ease of reaching otherwise inaccessible markets have increased significantly our risk of coming in contact with food containing infectious organisms. The education of industry, public health workers, governmental organizations, and consumers is the most effective means to prevent food-borne helminthic infections and safeguard the world's food supply. Prevention and intervention measures focused at the production level to disrupt the parasite's life cycle are critical for maintaining a safe food supply.

Diphyllobothrium dendriticum and Diphyllobothrium latum in fishes from southern Argentina: association, abundance, distribution, pathological effects, and risk of human infection.

Diphyllobothrium dendriticum and Diphyllobothrium latum are reported for the first time from Argentina. The following species from Lake Moreno (southern Argentina) were studied to determine whether plerocercoids were present: 11 brook trout (Salvelinus fontinalis), 32 perca (Percichthys sp.), 21 pejerrey (Patagonina hatcheri), and 114 rainbow trout (Oncorhynchus mykiss). Brook trout harbored both species (27.3% prevalence of D. dendriticum and 9.0% of D. latum); perca harbored only D. latum (18.7% prevalence); pejerrey were not infected and rainbow trout also harbored both species, with significant association. Diphyllobothrium latum was less abundant (1.4 plerocercoids/fish, 28.0% prevalence) than D. dendriticum (7.2 plerocercoids/fish, 57.8% prevalence) implying a lower health risk for humans. For both parasites, rainbow trout seem to be more important than the other host species studied. There is no evidence that either of the species is more harmful to the host. The lack of significant weight variation of the liver as related to intensity of infection strongly suggests that competition for energy is not an important aspect of the host pathology.

Five cases of Diphyllobothrium nihonkaiense infection with discovery of plerocercoids from an infective source, Oncorhynchus masou ishikawae.

Five persons from 2 families residing at Miyama Town, Mie Prefecture, Japan, ingested fresh raw fish Oncorhynchus sp. on 9 May 1999 that was caught at Owase district in Mie. They all expelled diphyllobothriid cestodes 11-37 days after ingesting the fish. The parasites were morphologically identical to Diphyllobothrium nihonkaiense Yamane et al., 1986. Five plerocercoids were detected from a portion of the fish. Nucleotide sequence of a region of the cytochrome c oxidase subunit I gene of mitochondrial DNA from an adult worm was identical with that from the plerocercoid. The fish was identified as Oncorhynchus masou ishikawae according to the nucleotide sequence of the nuclear ribosomal second internal transcribed spacer region II gene. This is the first record of D. nihonkaiense plerocercoids from O. m. ishikawae.

Natural transfer of helminths of marine origin to freshwater fishes with observations on the development of Diphyllobothrium alascense.

Infective stages of helminths of 5 species that occur as adults in marine mammals were found in burbot, Lota lota (L.) (Gadidae), from the lower Kuskokwim River (southwestern Alaska): Diphyllobothrium alascense Rausch et Williamson, 1958; Pyramicocephalus phocarum (Fabricius, 1780); Corynosoma strumosum (Rudolphi, 1801); Corynosoma semerme (Forsell, 1904); and Pseudoterranova decipiens (Krabbe, 1878). Some larval stages were obtained also from smelt, Osmerus mordax dentex Steindachner, an anadromous fish important as prey of burbot. Burbot, which are freshwater fish, could become paratenic hosts of those helminths by means of at least 3 interactions: by consuming marine fishes in brackish waters at river mouths, by feeding on marine fishes that enter lower reaches of rivers, or by preying on anadromous fishes as they migrate up rivers. Consumption of burbot by people may result in infection by helminths of marine origin; of those recorded, only P. decipiens may be significantly pathogenic. Attempts to rear P. phocarum in dogs were unsuccessful. Plerocercoids of D. alascense, of very small size and found only in the gastric lumen of burbot, readily infected dogs. For study of their development, strobilae were obtained at intervals of 48 hr to 32 days postinfection. In heavy infections, some strobilae developed slowly, while others underwent rapid development.

Current situation of human diphyllobothriasis in Europe.

Diphyllobothriasis, a parasitosis caused by the flatworm Diphyllobothrium latum, is contracted by consuming raw or undercooked freshwater fish. The aim of this study was to evaluate the situation of this parasitosis during the past 20 years in Europe through the analysis of databases and search engines (Medline, Cabi Helminthological abstracts,Yahoo, Google), and through a questionnaire sent to a network of European parasitologists and to microbiological laboratories located on the shores of the large Alpine lakes. This study has shown that several dozen cases have been reported each year in Finland and Sweden, that there have been numerous cases in the French or Italian speaking areas of subalpine lakes, and that sporadic cases only have been observed in Austria, Spain, Greece, Romania, Poland and Norway. Over 30 cases have been identified on the Swiss shores of Lake Maggiore since 1990, and 70 cases on the Swiss and French shores of Lake Leman between 1993 and 2002. Eight to 12% of perch fillets from Lake Leman and 7.8 % of perch from Lake Maggiore were infested with larvae. Contamination sources include marinated fish fillets in northern Europe, 'carpaccio di persico' in northern Italy, and perch and charr consumed raw or undercooked around Lake Leman. Factors allowing the continuation of the parasitic cycle include the continued dumping of wastewater into lakes, yachtsmen who also fish, and a possible animal reservoir.