A regional study of the zoonotic broad tapeworm Dibothriocephalus spp. in Northwestern Patagonia (Argentina): origin of fishes and coastal cities as factors affecting infection in fishes.

Diphyllobothriosis was first recorded in humans in Argentina in 1892 and in introduced salmonids in 1952. The aim of this work is to assess factors influencing the values of prevalence and abundance of plerocercoids in fishes that could increase the risk of transmission of Dibothriocephalus spp. in Andean Patagonian lakes. We analysed two key issues potentially related to the occurrence of tapeworms in fish: the presence of cities on coastlines (as potential sources of eggs to nearby lakes) and the difference between native and exotic fishes in susceptibility to infection. We investigated the probability of finding parasites in fish, the variation in parasite abundance in different environments and the relationship between host length and occurrence of plerocercoids. A total of 3226 fishes (belonging to six autochthonous and four introduced species) were analysed between 2010 and 2019 in eight environments. Plerocercoids were counted, and a subset was determined molecularly to species level. Two species, Dibothriocephalus latus and Dibothriocephalus dendriticus, were identified from both salmonids and native fishes, this being the first molecular confirmation of these tapeworm species parasitizing native South American fishes. Salmonids had higher levels of infection than native fishes, and these levels were higher in aquatic environments with a city on their coastline. Transmission to humans seems to occur mainly through Oncorhynchus mykiss, which showed the highest infection values and is the species most captured by fishers. Based on previous data and the present results, eggs shed by humans, dogs and gulls in cities could be the principal factors in maintaining the life cycle of this parasite in surrounding aquatic environments.

[(THE CURRENT SITUATION OF DIPHYLLOBOTHRIASIS: EPIDEMIOLOGY AND EPIDEMIOLOGICAL SURVEILLANCE)].

The paper analyzes the etiology of diphyllobothriasis pathogens and their distribution in the world. It estimates the infection rate of the population with tapeworms, the value of different fish species and procedures for their cooking as factors for transmission of Diphyllobothrium to the population and the risk for infection with tapeworms through infected foods. Epidemiological surveillance measures in different (synanthropic and natural) foci of diphyllobothriasis and with various types of pathogens are considered.

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.

[Parasitological monitoring as part of epidemiological surveillance of helminthiasis in the Russian Federation].

The paper presents data on the prevalence of helminthiasis in Russia on the basis of the State Reports on the sanitary and epidemiological situation in the Russian Federation. It comparatively characterizes morbidity rates in 2010-2012. Morbidity analysis has revealed the main reasons for the prevalence of parasitic diseases and the possible ways of their elimination.

Update on the human broad tapeworm (genus diphyllobothrium), including clinical relevance.

SUMMARY: Tapeworms (Cestoda) continue to be an important cause of morbidity in humans worldwide. Diphyllobothriosis, a human disease caused by tapeworms of the genus Diphyllobothrium, is the most important fish-borne zoonosis caused by a cestode parasite. Up to 20 million humans are estimated to be infected worldwide. Besides humans, definitive hosts of Diphyllobothrium include piscivorous birds and mammals, which represent a significant zoonotic reservoir. The second intermediate hosts include both freshwater and marine fish, especially anadromous species such as salmonids. The zoonosis occurs most commonly in countries where the consumption of raw or marinated fish is a frequent practice. Due to the increasing popularity of dishes utilizing uncooked fish, numerous cases of human infections have appeared recently, even in the most developed countries. As many as 14 valid species of Diphyllobothrium can cause human diphyllobothriosis, with D. latum and D. nihonkaiense being the most important pathogens. In this paper, all taxa from humans reported are reviewed, with brief information on their life history and their current distribution. Data on diagnostics, epidemiology, clinical relevance, and control of the disease are also summarized. The importance of reliable identification of human-infecting species with molecular tools (sequences of mitochondrial genes) as well as the necessity of epidemiological studies aimed at determining the sources of infections are pointed out.

Marine fish imported from Argentina as source of human diphyllobothriosis in Europe? Ecological evidence from dolphins.

Diphyllobothriosis caused by the Pacific broad tapeworm Adenocephalus pacificus (syn. Diphyllobothrium pacificum) is an emerging parasitic disease reported also from non-endemic areas, including Europe (Spain). The origin of these human cases is unknown but should be related to fresh marine fish imported from endemic areas. In this study, we molecularly confirmed common dolphins Delphinus delphis off Argentina as euparatenic transit hosts of A. pacificus. Preliminary analysis of their stomach content, together with data from previous studies from the Southwest Atlantic, showed that common dolphins feed almost exclusively on schooling Argentine hake Merluccius hubbsi and Argentine anchovy Engraulis anchoita. Therefore, we suggest that Argentine hake and Argentine anchovy may represent the intermediate hosts of A. pacificus in the Southwest Atlantic, but also in Europe to where M. hubbsi is imported on ice (unfrozen).

First confirmed human case of Diphyllobothrium stemmacephalum infection and molecular verification of the synonymy of Diphyllobothrium yonagoense with D. stemmacephalum (Cestoda: Diphyllobothriidea).

Several tapeworm species in the genus Diphyllobothrium Cobbold, 1858 have uncertain taxonomic positions, leading to taxonomic confusion as well as misdiagnosis of infections. Taxonomic revision based on DNA sequence analysis is considered necessary to resolve the taxonomy of several cases, including that between Diphyllobothrium stemmacephalum, the type species of the genus, and Diphyllobothrium yonagoense. Diphyllobothrium yonagoense was synonymized with D. stemmacephalum based on morphological observations by Andersen (1987), however no molecular studies have been undertaken to verify the validity of this synonymization. In the present study, the first human case confirmed molecularly as D. stemmacephalum infection is reported, and the validity of the synonymization of D. yonagoense with D. stemmacephalum was assessed based on molecular phylogenetics. Diphyllobothrium stemmacephalum and D. yonagoense grouped into the same clades with high bootstrap confidence values for both cox1 and nad3. Genetic distances between the two taxa were very small (0.000-0.012 and 0.000-0.017 for cox1 and nad3, respectively) and were considered to fall within the range of intraspecific variation. Using these molecular analyses, this study verified molecularly that D. yonagoense is a junior synonym of D. stemmacephalum. Further, the closer phylogenetic relationship between D. stemmacephalum and Diplogonoporus species rather than other diphyllobothriids, including Diphyllobothrium nihonkaiense and Diphyllobothrium latum, was corroborated. The genus name for D. nihonkaiense and D. latum is also discussed.

[Prevalence of Diphyllobothrium latum, L., 1758 infestation in Perca fluviatilis from Lake Leman]. / Prévalence de l'infestation par Diphyllobothrium latum, L., 1758 chez les Perches (Perca fluvatilas) du lac Léman.

Diphyllobothriasis is contracted by consuming raw or undercooked freshwater fish and is still present on the shores of lake Leman. The aim of this study was to evaluate the prevalence of Diphyllobothrium latum plerocercoid larvae in Perca fluviatilis from this lake. Four to 10% of perch fillets examined in November 2003, February 2004, April 2004 and January 2005, were infested with D. latum larvae. The identification of the larvae was confirmed by PCR and sequencing of the 18S rDNA.

Diphyllobothriasis associated with salmon consumption in Pacific Coast states.

A review of requests for niclosamide ( Niclocide or Yomesan ) made to the Centers for Disease Control Parasitic Diseases Drug Service indicated that an outbreak of diphyllobothriasis occurred in west coast states in 1980, and in the Los Angeles area in 1981. Our investigation of 52 infections that occurred in 1980 implicates fresh salmon (Oncorhynchus spp.) as the host for the Diphyllobothrium parasite in 82% of the persons interviewed. We describe here common symptoms of the infection, methods of fish preparation employed by infected individuals, and epidemiologic data. We suggest that changes in fish marketing practices and the popularity of uncooked or slightly cooked fresh salmon were responsible for this epidemic. We recommend that salmon be either cooked or frozen before it is eaten.

Identification of the copepod intermediate host of the introduced broad fish tapeworm, Diphyllobothrium latum, in Southern Chile.

The broad fish tapeworm, Diphyllobothrium latum, is an exotic species in both Chile and Argentina, and until now, its copepod host has remained unknown in South American waters. The objective of this study was to identify calanoid copepod species that may be intermediate hosts for D. latum in Lake Panguipulli, Chile. In this lake, the highest levels of infection by this tapeworm occur in the introduced rainbow trout, Oncorhynchus mykiss. Of the 2 calanoid copepods found in Lake Panguipulli, Diaptomus diabolicus and Boeckella gracilipes, only D. diabolicus became infected on experimental exposure to coracidia. Prevalence (mean intensity) of experimental infection in adult copepods was 73.2% (2.8 procercoids per host). Diaptomus diabolicus has been demonstrated to be a new intermediate host; this is the first record of a copepod host for D. latum in South America.

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.

Aggregation of helminths: the role of feeding behavior of fish hosts.

Individual Arctic charr (Salvelinus alpinus) from Fjellfrøsvatn, northern Norway, could be categorized by their stomach contents as zooplanktivores or benthivores. Feeding specialization among these fish was evident from negative correlations between helminths transmitted by pelagic copepods (Diphyllobothrium dendriticum and D. ditremum) and those transmitted by the benthic amphipod Gammarus lacustris (Cystidicola farionis and Cyathocephalus truncatus). Occurrences of parasite species acquired from the same types of invertebrate were positively correlated in the fish. Strong relationships among habitat use, diet, and helminth infections among the Arctic charr indicated persistent foraging patterns involving long-term habitat use and feeding specialization. The distribution of all parasite species was highly aggregated in the fish samples, measured by the exponent k of the fitted negative binomial distributions (range: 0.5-7.5) and the variance-to-mean ratios (s2/mean, range: 5-85). Charr specializing on either copepods or Gammarus predominantly contributed to high-intensity class intervals within the overall frequency distributions of the corresponding parasite species. Such fish had low infection intensities of helminths transmitted by other prey organisms. The detailed analyses of the parasite frequency distributions for fish with different habitat or feeding preferences evidently show how heterogeneity in trophic behavior contributes strongly to the commonly observed aggregation of helminths among hosts under natural conditions.

Prevalence of larval Anisakis simplex in pen-reared and wild-caught salmon (Salmonidae) from Puget Sound, Washington.

The abundance of parasites of public health significance in pen-reared salmon and wild-caught salmon was compared. Two hundred eighty-seven salmon from Puget Sound, Washington, were examined for third-stage larvae of Anisakis simplex. Of these fish, 237 Atlantic salmon (Salmo salar), coho salmon (Oncorhynchus kisutch) and chinook salmon (O. tshawytscha) were reared in commercial salmon pens and 50 sockeye salmon (O. nerka) were caught during their spawning migration. All wild-caught salmon were found to be infected with larval A. simplex; conversely, all pen-reared fishes lacked such infections. Edible musculature of wild salmon were infected with 581 (87%) nematode larvae. Of other salmon parasites known to infect humans, one Diphyllobothrium sp. plerocercoid was collected from each of three of the 50 wild-caught salmon. The study showed that farmed salmon may increase the margin of safety for consumers of raw seafood.

Cestode zoonoses of aquatic animals.

The cestode zoonoses of Diphyllobothrium, and Spirometra and Sparganosis are discussed from the point of view of their transmission and epidemiology.

[Epidemiology of diphyllobothriasis in the Valdivia river basin, Chile]. / Epidemiología de la difilobotriasis en la cuenca del Río Valdivia, Chile.

In the Valdivia (Chile) river basin 1,295 inhabitants of 6 riverside districts were examined between March and October 1987 and showed a 1.2% of prevalence by Diphyllobothrium in the districts of Riñihue and Las Huellas. Prevalence of 5.3% and 9.8% respectively were registered in dogs of the districts of Riñihue and Malihue. No cat or pig infection was observed in the different districts. The parasites recovered after the treatment were identified as Diphyllobothrium latum. Human infection by D. latum in the districts affected results from the consumption of smoked or insufficiently cooked fish. The investigation of 1,450 fish (4 exotic species and 11 autochthonous ones), caught in the Valdivia river basin in 1986 and 1987, showed the existence of plerocercoids of D. latum and/or Diphyllobothrium dendriticum in Salmo gairdneri and Salmo trutta among exotic fish and in some autochthonous species. Prevalence and mean intensity in the infection of fish as well as the degree of aggregation in the infrapopulations varied in the different districts. Some species of fish would act as intermediary hosts and others as paratenic hosts in the life cycles of Diphyllobothrium spp. in the Valdivia river basin. An improvement in the conditions of basic sanitation, in sanitary education and in the treatment of infected persons is proposed as a means for the control of diphyllobothriasis in the districts affected.

[Epidemiology of Diphyllobothrium latum infection in Japan, with special reference to infection of cherry salmon].

The most characteristic difference of Japanese Diphyllobothrium latum from those of European and Canadian species is it's second intermediate host. The Japanese Diphyllobothrium latum take genus Oncorhynchus as it's most important 2nd intermediate host and plerocercoids are always found in their fillet not in their viscera which phenomena can not be observed in the cases of the latter Diphyllobothrium. From 1977 to 1982, we examined 723 Cherry salmon, Oncorhynchus masou which were caught in the northern Japan Sea from March to May every year. Out of 723 Cherry salmon, 218 (30.2%) were showed the infection of plerocercoids of D. latum (Table 1 & 2). The yearly data of the infection rate of fish varied from 15.9 to 48.4%. The plerocercoids were found most likely in the back hind part of the fish (Figure 1). The sex ratios (Table 4) of Cherry salmon caught in the Japan Sea indicated that these salmon was mainly derived not from Japanese rivers, but from Kamchatka, Sakhalin or the coastal part of Siverian continent (Table 3.) It remains totally unknown where these Cherry salmon got infection of D. latum.

[An evaluation using an information analysis method of the environmental factors affecting the diphyllobothriasis situation in water reservoirs]. / Otsenka metodom informatsionnogo analiza faktorov okruzhaiushchei sredy, vliiaiushchikh na situatsiiu po difillobotriozu na vodokhranilishchakh.

Information analysis was used to assess the influence of certain anthropogenic factors on the situation in water reservoirs of the Daugava, Dnieper, Don, Volga, Kama, Ob, Yenisei, Amu Darya and Zeya river basins with respect to diphyllobothriasis.

[An experimental study of the susceptibility of the snakehead Ophiocephalus argus to infestation by larvae of the tapeworm Diphyllobothrium latum]. / Eksperimental'noe izuchenie zarazhaemosti zmeegolova Ophiocephalus argus lichinkami lentetsa shirokogo Diphyllobothrium latum.

Experiments were made to infect young Ophiocephalus argus, the fish of prey delivered from eastern Asia in the Amu-Dar'ya River basin, outside the area of the broad tapeworm Diphyllobothrium latum. The dalags were infected mainly by ingesting the local copepods Arctodiaptomus salinus, the experimentally invaded larvae of the broad tapeworm. The latter larvae were obtained from the development of eggs of the helminth isolated from strobilae from the patients treated in Perm Province. D. latum plerocercoids lived in the dalags nearly 3 weeks, then they died and lysed. Thus, the dalag cannot be a supplementary host of D. latum.