Roman Kuchta

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.

Revision of the order Bothriocephalidea Kuchta, Scholz, Brabec & Bray, 2008 (Eucestoda) with amended generic diagnoses and keys to families and genera

The tapeworm order Bothriocephalidea Kuchta, Scholz, Brabec & Bray, 2008 (Platyhelminthes: Eucestoda), which has until recently formed part of the suppressed order Pseudophyllidea, is revised. Four new genera, namely Andycestus n. g. [type- and only species A. abyssmus (Thomas, 1953) n. comb.], Plicocestus n. g. [type- and only species P. janickii (Markowski, 1971) n. comb.] (both Bothriocephalidae), Mesoechinophallus n. g. [type-species M. hyperogliphe (Tkachev, 1979) n. comb.; other species M. major (Takao, 1986) n. comb. (Echinophallidae)] and Kimocestus n. g. [type- and only species K. ceratias (Tkachev, 1979) n. comb.] (Triaenophoridae) are proposed. Parabothriocephaloides Yamaguti, 1934, Penetrocephalus Rao, 1960 and Tetracampos Wedl, 1861 are resurrected as valid genera, whereas Alloptychobothrium Yamaguti, 1968 (newly synonymised with Plicatobothrium Cable & Michaelis, 1967), Capooria Malhotra, 1985 and Coelobothrium Dollfus, 1970 (syns of Bothriocephalus Rudolphi 1808), Fissurobothrium Roitman, 1965 (syn. of Bathybothrium Lühe, 1902), Paratelemerus Gulyaev, Korotaeva & Kurochkin, 1989 (syn. of Parabothriocephaloides Yamaguti, 1934) and Tetrapapillocephalus Protasova & Mordvinova, 1986 (syn. of Oncodiscus Yamaguti, 1934) are considered to be invalid. A recently erected genus, Dactylobothrium Srivastav, Khare & Jadhav, 2006, and its type- and only species, D. choprai Srivastav, Khare & Jadhav, 2006, are considered to be unrecognisable, because their descriptions contain a number of obvious errors and also indicate that a mixture of several taxa, probably of at least two cestode orders, were studied. Parabothriocephaloides wangi nom. nov. is proposed for Parabothriocephalus psenopsis Wang, Liu & Yang, 2004 from Psenopsis anomala in China in order to avoid a secondary homonymy. All 46 genera considered to be valid are revised, with their generic diagnoses amended on the basis of a critical examination of extensive museum and newly collected specimens. Despite apparent paraphyly or polyphyly of some bothriocephalidean families, especially the Triaenophoridae, the current classification restricted to four families, proposed by Bray et al. (1994), namely the Bothriocephalidae, Echinophallidae, Philobythiidae and Triaenophoridae, is provisionally retained with slight modifications until more molecular data on most genera are available. Keys to families and genera are provided.

Spermatozoon ultrastructure of the pseudophyllidean cestode Paraechinophallus japonicus, a parasite of deep-sea fish Psenopsis anomala (Perciformes, Centrolophidae)

This paper provides the first ultrastructural data on the spermatozoon of a pseudophyllidean cestode belonging to the family Echinophallidae, Paraechinophallus japonicus, parasitizing deep-sea fish Psenopsis anomala from Japan. The mature spermatozoon contains two axonemes of the 9+“1” trepaxonematan pattern, nucleus, cortical microtubules, and electron-dense granules. Its anterior extremity exhibits a single electron-dense crested body. One of the most interesting features of the mature spermatozoon is the presence of a ring of tubular structures encircling the axoneme. This character, previously reported in species of the families Bothriocephalidae and Triaenophoridae, may be unique to pseudophyllideans of the group “Bothriocephalidea”, thus supporting the assumption that the order Pseudophyllidea is formed in fact by two unrelated clades; “Bothriocephalidea” and “Diphyllobothriidea”. The posterior extremity contains the posterior part of the nucleus and the disorganized axoneme—a character previously not described in the Eucestoda.

Tapeworms (Cestoda: Proteocephalidea) of Fishes from the Amazon River in Peru

Abstract This article provides the first data on the occurrence of adult proteocephalidean tapeworms (Cestoda) in freshwater fishes from the Peruvian part of the Amazon River. In total, 29 species of proteocephalidean cestodes of the genera Amphoteromorphus, Chambriella, Choanoscolex, Euzetiella, Houssayela, Mariauxiella, Monticellia, Nomimoscolex, Nupelia, Peltidocotyle, Proteocephalus, Rudolphiella, Scholzia, Sciadocephalus, Spatulifer, Travassiella, and Zygobothrium are reported from 10 species of pimelodid, heptapterid and doradid catfish and the cichlids Astronotus ocellatus and Cichla monoculus. All species are reported from western Amazonia and Peru for the first time, with 6 taxa representing new geographical records for the Amazon River basin. The most remarkable finding is that of Houssayela sudobim (Woodland, 1935) from Pseudoplatystoma fasciatus, reported for the first time since its original description. Four other taxa (Chambriella sp. and Proteocephalus sp. from Phractocephalus hemioliopterus, Nupelia sp. from Goeldiella eques, and Proteocephalus sp. from Pterodoras granulosus) may be new for science. A list of the species found is provided together with brief comments on their fish hosts and geographical distribution. In addition to adult tapeworms, larvae (metacestodes) of proteocephalideans were found encysted in the mesenteries, intestinal wall, and gills of small catfish.

Tapeworm Diphyllobothrium dendriticum (Cestoda)--neglected or emerging human parasite?

Background A total number of 14 valid species of Diphyllobothrium tapeworms have been described in literature to be capable of causing diphyllobothriosis, with D. latum being the major causative agent of all human infections. However, recent data indicate that some of these infections, especially when diagnosed solely on the basis of morphology, have been identified with this causative agent incorrectly, confusing other Diphyllobothrium species with D. latum. Another widely distributed species, D. dendriticum, has never been considered as a frequent parasite of man, even though it is found commonly throughout arctic and subarctic regions parasitizing piscivorous birds and mammals. Recent cases of Europeans infected with this cestode called into question the actual geographic distribution of this tapeworm, largely ignored by medical parasitologists. Methodology and Results On the basis of revision of more than 900 available references and a description and revision of recent European human cases using morphological and molecular (cox1) data supplemented by newly characterized D. dendriticum sequences, we updated the current knowledge of the life-cycle, geographic distribution, epidemiological status, and molecular diagnostics of this emerging causal agent of zoonotic disease of man. Conclusions The tapeworm D. dendriticum represents an example of a previously neglected, probably underdiagnosed parasite of man with a potential to spread globally. Recent cases of diphyllobothriosis caused by D. dendriticum in Europe (Netherlands, Switzerland and Czech Republic), where the parasite has not been reported previously, point out that causative agents of diphyllobothriosis and other zoonoses can be imported throughout the world. Molecular tools should be used for specific and reliable parasite diagnostics, and also rare or non-native species should be considered. This will considerably help improve our knowledge of the distribution and epidemiology of these human parasites.

A Comparative Study of Eubothrium Salvelini and E. crassum (Cestoda: Pseudophyllidea) Parasites of Arctic Charr and Brown Trout in Alpine Lakes

We compared the morphology, morphometry, and some aspects of the biology and ecology of Eubothrium crassum and E. salvelini, two pseudophyllidean tapeworms in brown trout, Salmo trutta m. lacustris, and Arctic charr, Salvelinus alpinus, in lakes of the western part of the Alps. The taxonomic importance of the apical disc for the discrimination of both taxa was confirmed. The apical disc of E. crassum is rectangular, possessing two deep grooves above the bothriae and 2–16 additional indentations. In E. salvelini, the apical disc is bibbed and bilaterally symmetric. We found new and significant interspecific differences in the length and width of the scolex, the diameter of the apical disc, and the width of the neck, with all measurements being larger in E. crassum. The two species differ in the number and size of the testes (fewer and larger in E. salvelini), the length of the cirrus sac (longer in E. crassum), and the size of vitelline follicles (larger in E. salvelini). Vitelline follicles of E. crassum are always cortical and sometimes enter into the outermost muscle fibres, whereas follicles of E. salvelini are situated largely medullary with few follicles entering between the innermost bundles of muscles. The eggs and the oncospheres of E. salvelini are larger. The embryonic hooks of E. crassum measure 14–18 µm whilst those of E. salvelini are 18–26 µm. For both taxa, the intraspecific variability in morphometric characters was fairly low. The prevalence and intensity of infection of E. crassum and E. salvelini in their respective fish hosts were very high (prevalence 90–94%; mean intensity 36.3 and 6.6, maximums of 172 and 63 tapeworms per fish, respectively). E. salvelini eggs were spontaneously released throughout the year except for winter months; E. crassum laid eggs only in summer (June—August). Natural infection of copepods with Eubothrium procercoids was very low (prevalence 0.002%). The morphogenesis of Eubothrium procercoids was studied in an intermediate host, the copepod Cyclops prealpinus, that had been simultaneously infected with both species.

Molecular phylogeny of the Bothriocephalidea (Cestoda): molecular data challenge morphological classification.

In this study, the relationships of the cestode order Bothriocephalidea, parasites of marine and freshwater bony fish, were assessed using multi-gene molecular phylogenetic analyses. The dataset included 59 species, covering approximately 70% of currently recognised genera, a sample of bothriocephalidean biodiversity gathered through an intense 15year effort. The order as currently circumscribed, while monophyletic, includes three non-monophyletic and one monophyletic families. Bothriocephalidae is monophyletic and forms the most derived lineage of the order, comprised of a single freshwater and several marine clades. Biogeographic patterns within the freshwater clade are indicative of past radiations having occurred in Africa and North America. The earliest diverging lineages of the order comprise a paraphyletic Triaenophoridae. The Echinophallidae, consisting nearly exclusively of parasites of pelagic fish, was also resolved as paraphyletic with respect to the Bothriocephalidae. Philobythoides sp., the only representative included from the Philobythiidae, a unique family of parasites of bathypelagic fish, was sister to the genus Eubothrium, the latter constituting one of the lineages of the paraphyletic Triaenophoridae. Due to the weak statistical support for most of the basal nodes of the Triaenophoridae and Echinophallidae, as well as the lack of obvious morphological synapomorphies shared by taxa belonging to the statistically well-supported lineages, the current family-level classification, although mostly non-monophyletic, is provisionally retained, with the exception of the family Philobythiidae, which is recognised as a synonym of the Triaenophoridae. In addition, Schyzocotyle is resurrected to accommodate the invasive Asian fish tapeworm, Schyzocotyle acheilognathi (Yamaguti, 1934) n. comb. (syn. Bothriocephalus acheilognathi Yamaguti, 1934), which is of veterinary importance, and Schyzocotyle nayarensis (Malhotra, 1983) n. comb. (syn. Ptychobothrium nayarensis Malhotra, 1983). The genus is morphologically characterised by a wide, heart-shaped scolex with narrow, deep bothria.

Host specificity and geographical distribution of Eubothrium in European salmonid fish

The host specificity and distribution of Eubothrium crassum (Bloch, 1779) and Eubothrium salvelini (Schrank, 1790), morphologically fairly similar pseudophyllidean tapeworms parasitizing salmonid fish, were critically assessed on the basis of morphological and genetic evaluation of extensive material collected from different definitive hosts and geographical regions in Europe. Eubothrium crassum occurs in fish of the genera Salmo, i.e. salmon (S. salar - both freshwater and marine), sea trout (S. trutta trutta), brown trout (S. trutta fario), and lake trout (S. trutta lacustris), and also in Danubian salmon (Hucho hucho) and vendace (Coregonus albula). Eubothrium salvelini parasitizes Arctic char (Salvelinus alpinus) and brook trout (Salvelinus fontinalis) in Europe, and also whitefish (Coregonus wartmanni). Rainbow trout (Oncorhynchus mykiss), which is not a native European fish species, was found to be a suitable definitive host for both Eubothrium species, which may occur simultaneously in the same fish. Previous records of E. crassum in Arctic char and brook trout, and those of E. salvelini in fish of the genus Salmo were most probably misidentifications. Most studies of Eubothrium have involved salmonids from the northern part of Europe, with few records from southern and south-eastern Europe. This study also confirmed the reliability of the morphology of the apical disc for the discrimination of E. crassum and E. salvelini.

(Self-) infections with parasites: re-interpretations for the present

Previously, scientists sometimes resorted to infecting themselves or colleagues with parasites, usually to assess the pathogenicity and obtain insight into the life cycles of the parasites, host specificity, and epidemiology. However, with recent research addressing the possible beneficial impact of intestinal helminths on a range of immune-mediated diseases in humans, these studies offer valuable information, although many are now considered unethical owing to a lack of experimental oversight and informed consent. Here, we critically review cases in which humans were deliberately infected with parasites. Moreover, we summarize the contribution of (self-) infections and propose protist and helminth candidates, chosen on the basis of several criteria, to test as possible therapy for selected human diseases.

Bothriocephalidean tapeworms (Cestoda) of freshwater fish in Africa, including erection of Kirstenella n. gen. and description of Tetracampos martinae n. sp.

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