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The content of sodium, potassium, calcium, and magnesium ions was determined in cestodes Ligula intestinalis, Eubothrium rugosum, and Triaenophorus nodulosus. In freshwater fishes the total concentration of Na, K, Ca, Mg ions in cestode tissue water is practically similar to that of fishes muscles and in serum. It was suggested that examined cestodes have isoosmotic regulation of the water-salt balance.
Between February 1989 and January 1990 a total of 801 red foxes were examined for the presence of cestodes. Echinococcus multilocularis could be noted with an infection rate of 11.6% in the small intestine of the red fox. The following other cestodes were found (in order of frequency) Taenia crassiceps (19.9%), Mesocestoides spp. (16.6%), Taenia polyacantha (7.0%), Hydatigena taeniaeformis (0.7%), Dipylidium caninum (0.5%) and Diphyllobothrium latum (0.5%). Infections with Echinococcus multilocularis very often showed worm numbers between 11 and 100 specimen per fox. The number of worms of the other cestodes mostly varied between one and ten specimen per animal.
Cestodes of the family Anoplocephalidae Cholodkovsky, 1902, in their adult form, parasitize a variety of hosts, including reptiles, birds and mammals. To complete their life cycle, an intermediate host is required. This study gives a critical review of the life cycles of genera principally important to veterinary medicine (but sporadically infecting man): Anoplocephalinae (Anoplocephala, Anoplocephaloides, Bertiella and Moniezia) and Thysanosomatinae (Avitellina, Stilesia, Thysaniezia and Thysanosoma), using data reported by others and our own observations. The accepted paradigm on the biology of the anoplocephalid cestodes is that oribatid mites (Acarina) serve as intermediate hosts. However, as regards the genera Avitellina, Thysaniezia and Thysanosoma, it is still unclear whether oribatid mites are indeed the intermediate hosts, as larval forms (cysticercoids) have also been found in collembolans and psocids. Using the controversial biological cycle of Thysanosoma actinioides (Diesing, 1834), a theoretical methodological research proposal for parasitology was constructed which attempts to define a conceptional mark enabling us to predict and explain the parasite-hosts' related phenomenon. Aspects of this proposal are discussed using the biology of the cestodes of family Anoplocephalidae, as examples.
1. Natural abundance carbon-13 nmr spectra of several intact cestodes have been obtained. 2. All spectra show peaks assignable to triglycerides and the N(CH3)3 carbons of the choline moiety. 3. The olefinic region of the 13C nmr spectra indicated that the cestode larvae Mesocestoides corti and Echinococcus multilocularis have a larger concentration of polyunsaturated fatty acids than Hymenolepis adults. 4. Mobile fragments of glycogen were detected in all species studied, but its apparent concentration in individual cestodes was highly variable.
Several hundred million years ago, the free-living ancestors of all extant helminth parasites decided to colonize entirely new habitats, the bodies of other metazoan animals. As a consequence of the resulting adaptation processes, they evolved highly complex life-cycles in which many developmental transitions were initiated and controlled by host-derived signals. Understanding the molecular basis of the original developmental mechanisms, and the modifications that occurred during co-evolution with the host, is not only fundamental to our understanding of parasitism but also highly relevant for the design of anti-parasitic drugs and vaccines. In the past several years, molecular investigations on parasitic nematode and trematode development have made considerable progress and, supported by respective genome sequencing projects and emerging methods of genetic manipulation, will be a flourishing field in the years to come. We consider it time that corresponding studies are also pushed for the third large group of parasitic helminths, the cestodes. Here, we review the first experimental steps into that area, which have been undertaken recently. We report on cestode genomics, the identification of signaling factors associated with larval development, and the establishment as well as improvement of in vitro cultivation systems by which cestode life-cycles can be studied in the laboratory.
Eucestodes have a simple aceolomate body structure and are conservative in terms of the numbers and nature of their cell types. Nevertheless, the cestodes form a diverse group with many strikingly different forms distinguished by the structure of their holdfasts, sexual tissues and embryos. These morphological adaptations have their origins in subtle variations in the structure of their cells and extracellular matrices. This review is concerned with the biology of eucestode epithelia and examines their structure and functions, interrelationships with other tissues, and gives insight into how their components are modified among the many taxa. Three features of cestode epithelia, namely, the occurrence of regional specialisation, microtriches and secretory components, are described. In addition, evidence is presented to suggest that some cestode epithelia are involved in developmental processes such as the nurture of embryos and maintenance of surrounding tissues.
The flatworm mitochondrial genetic code, which has been used for all species of the Platyhelminthes, is mainly characterized by AUA codon for isoleucine, AAA codon for asparagine and UAA codon for tyrosine. In eight species of cestodes (Echinococcus multilocularis, Echinococcus granlosus, Taenia solium Taenia saginata, Taenia hydatigena, Taenia crassiceps, Hymenolepis nama and Mesocestoides corti), the cytochrome c oxidase subunit I (COI) genes were partially sequenced to verify this genetic code. Comparison of the COI-encoding nucleotide sequences with those of human, sea urchin, fruit fly, nematode and yeast indicated that the assignments of AUA and AAA codons are adequate for cestodes. In addition, the nucleotide sequences of ATPase subunit 6 (ATP6) gene and its flanking region were compared to examine initiation and stop codons. In the related species of T. solium and T. saginata, the deduced amino acid sequences of ATP6 were homogeneous; however, the conversion of initiation codon AUG into GUG was observed in T. saginata. We also found the similar conversion in T. crassiceps. The C-terminal sequences of putative ATP6 proteins were highly conserved among the eight species and the stop codon UAG was altered to UAA in all Taenia species. The features of the gene-junctional region between NADH dehydrogenase subunit 4 (ND4) and glutamine tRNA (tRNAGln) genes also supported that UAA serves as a stop codon. Based on these results, we propose that the flatworm mitochondrial code should be modified for cestodes, particularly, in an initiating methionine codon (GUG) and a terminating codon (UAA).
Total DNAs, isolated from a range of taeniid cestodes (Taenia solium, T. saginata, T. pisiformis, T. crassiceps, T. hydatigena, T. ovis, T. multiceps and T. taeniaeformis), have been subjected to restriction enzyme digestion, Southern transfer and hybridization analysis using cloned fragments of the ribosomal RNA gene of Schistosoma mansoni. Substantial inter-specific genetic differences have been revealed on the basis of characteristic hybridization patterns for each of the taeniid cestode species. Furthermore, a random genomic DNA library has been constructed in the vector plasmid pAT153 using DNA extracted from a pig isolate (Indian origin) of T. solium. A panel of taeniid cestode DNAs including DNA from Echinococcus granulosus, has been used in conjunction with hybridization and restriction enzyme analysis to identify in the library a single recombinant plasmid with a T. solium-specific insert (coded pTS10) and two recombinant plasmids with T. solium inserts having selective specificities for T. solium and T. ovis (coded pTS17) and T. solium, T. saginata, T. ovis and T. multiceps (coded pTS28). These recombinant plasmids and the cloned fragments of the ribosomal RNA gene of S. mansoni have been used in restriction endonuclease, Southern transfer and hybridization analysis to detect intra-specific genetic variation in cysticerci of T. solium from India, Mexico and Zimbabwe. In addition, pTS10 and pTS17 have been used in a simple dot-blot assay to distinguish T. solium from T. saginata.
It recently became clear that acanthocephalans parasitizing mammals can bioconcentrate several heavy metals to conspicuously higher concentrations than the tissues of their definitive hosts. As cestodes are more abundant in terrestrial animals than acanthocephalans, and thus potentially more useful in attempts toward passive as well as active biomonitoring, a very common tapeworm and its synanthropic mammalian host were selected for the present study. The tapeworm Hymenolepis diminuta and experimentally infected male Wistar rats of the CD-M-strain were investigated with respect to their lead accumulation. The worms were allowed to grow up for five weeks post infection followed by a five weeks oral lead exposure of the rats. After the exposure period the rats were killed and the metal levels were determined in muscle, liver, intestine, testes and kidney of the rats as well as in the parasites. Lead concentrations were found to be 17 times higher in the cestodes than in kidney, whereas metal levels in all other host tissues were below the detection limit. Thus, this study reveals that lead accumulation also occurs in cestodes parasitizing mammals. Due to a lack of adequate sentinel species in terrestrial habitats the host-parasite-system rat-H. diminuta appears to be a useful and promising bioindication system especially in urban ecosystems.
Cestode communities in Podiceps cristatus, P. grisegena, P. nigricollis and Tachybaptus ruficollis during their migrations and overwintering are studied at the Bulgarian Black Sea coast. The infracommunities exhibit high richness, abundance and dominance, and low diversity and similarity. The component communities have a similar taxonomic structure at the levels higher than species, a small number of core species and a high portion of grebe specialists in the richness and abundance. The comparison with cestode communities in grebes from Canada (Stock & Holmes, 1987) reveals several differences and similarities. The higher richness and abundance of the infracommunities in Canada are explained by the constant conditions of breeding habitats enhancing higher transmission rates. At the component community level, there is a significant difference between the two species lists. The degree of parasite exchange among the grebe species in Bulgaria is lower. Several characters of cestode component communities in grebes do not depend on either historical factors or different habitats. These are the similar patterns of the taxonomic structure at the levels higher than species, almost the same list of generalists, the participation of specialists of anatids, and the leading role of grebe specialists in the structure.
An identical 36-nucleotide exon was identified at the 5' termini of different mRNAs from the cestode Echinococcus multilocularis. We provide evidence that this exon constitutes a new spliced leader (SL) that is obviously trans-spliced to echinococcal pre-mRNAs, donated by a non-polyadenylated, trimethylguanosine-capped SL-RNA of 104 nucleotides. Sequence comparisons indicated that cestode and trematode SLs are likely to be derived from a common ancestor gene. No conservation was, however, observed concerning the spectrum of mRNAs that is trans-spliced in cestodes and trematodes, indicating that trans-splicing of a particular flatworm mRNA is not correlated with the function of the encoded protein. We also show that the echinococcal gene elp, encoding a member of the ezrin/radixin/moesin protein family, is expressed via two alternative transcripts, spliced either cis or trans at an identical splice acceptor site. This was accompanied by the formation of different elp primary transcripts, harboring a complete or a truncated upstream intron, which supports the hypothesis that alternative cis/trans-splicing depends on the presence or absence of an upstream splice donor site. A putative SL gene was also identified on chromosomal DNA of Echinococcus granulosus, indicating widespread utilization of trans-splicing in the genus.
Parasites impose an energetic cost upon their hosts, yet, paradoxically instances have been reported in which infection is associated with enhanced, rather than diminished, host growth rates. Field studies of these parasite effects are problematic, since the pre-infection condition of the hosts is generally unknown. Here, we describe a laboratory experiment in which the growth rate and body condition of 76 laboratory-reared three-spined stickleback fishes were examined before, during and after each fish was fed the infective stage of the parasitic cestode Schistocephalus solidus. Twenty-one of these fishes went on to become infected by the cestode. Fishes were individually housed and provided with an abundant food supply to eliminate the potentially masking effects of variable competitive ability. Infection occurred independently of fish gender, size, body condition or pre-exposure growth rate. After exposure to the cestode, infected fishes grew faster (excluding parasite weight) and maintained a similar or better body condition compared with uninfected fishes, despite developing enlarged spleens. The accelerated growth could not be explained by reduced gonadal development. This result, one of few demonstrations of parasite-associated growth enhancement in fishes, is discussed with respect to other such parasite systems.
A hermaphroditic individual that prefers to outbreed but that has the potential of selfing faces a dilemma: in the absence of a partner, should it wait for one to arrive or should it produce offspring by selfing? Recent theory on this question suggests that the evolutionary solution is to find an optimal delay of reproduction that balances the potential benefit of outcrossing and the cost of delaying the onset of reproduction. Assuming that resources retained from breeding can be reallocated to future reproduction, isolated individuals, compared with individuals with available mates, are predicted to delay their age at first reproduction to wait for future outcrossing. Here, I present empirical support for this idea with experimental data from the hermaphroditic cestode Schistocephalus solidus. I show that individuals breeding alone delay their reproduction and initially produce their eggs at a slow rate relative to cestodes breeding in pairs. This delay is partly compensated for by a later higher egg production, although singly breeding cestodes still pay a cost of overall lower egg production.
Some digeneans and cestodes parasitic in a population of the white-faced ibis Plegadis chihi (Vieillot) from Buenos Aires province, Argentina, are presented. The digeneans Dietziella egregia (Dietz, 1909), Patagifer bilobus (Rudolphi, 1819), Ascocotyle (Leighia) hadra Ostrowski de Nuñez, 1992 and Posthodiplostomum nanum Dubois, 1937 from the intestine; Prosthogonimus ovatus (Rudolphi, 1803) from the cloaca; Athesmia heterolecithodes (Braun, 1899) from the bile ducts and the cestode Hymenolepis megalops (Nitzsch in Creplin, 1829) from the cloaca, were recorded. The discovery of D. egregia, P. ovatus, A. heterolecithodes and P. nanum constitute new host and/or new geographical records. Adults of A. (L.) hadra, previously described in experimental definitive hosts, are first reported from a naturally infected bird. Hymenolepis megalops, a cestode of Anseriformes is first reported from Ciconiiformes.
This study was performed to investigate the intestinal parasites (especially cestoda) in the guts of Theragra chalcogramma in Korea. The cestode larvae collected were morphologically observed and measured, and at the same time, microscopical study was done with the section slides of the cestode larvae. They were identified on the basis of the descriptions by Schmidt and Yamaguti. The results obtained in this study are as follows: The cestode larvae were identified as Khawia sinesis, Eulacistorhynchus chiloscyllius, Tentacularia coryphaenea, Pseudonybelinia odontacantha and Nybelinia lingualis. These are new species reported in Korea. The characteristics of Khawia sinesis are its scolex lacking loculi and broad, flat and fimbriate shape. Its neck is not separated from the body but a little constricted. Eulacistorhynchus chiloscyllius is characterized by fairly long and acraspedote scolex. The bulbs are long; retractor muscles are attached to bases of the bulbs. The two bothridia are oval or round in shape and lacking posterior notch. The tentacles are long and poeciloacanthus; double chainette present. Tentacularia coryphaenea is characterized by its long craspedote and subcylindrical scolex. The bothridia are separated, without free borders and spinous. The tentacles are short, slender, armed with solid hooks in spirals, similar except the base of tentacle. The tentacle sheaths are not twisted. The bulbs are ellipsoidal. Pseudonybelinia odontacantha is characterized by its craspedote scolex. The tentacles are inserted near anterior margin of bothridia and armed with hooks in spirals ascending left to right. The hooks are similar, throughout tentacle, with feeble curve and provided with a tooth-like protuberance on the ventral side. The bulbs are three times longer than its width. The posterior margins of bothridia have a pair of eversible ciliated pits; or fossettes. Nybelinia lingualis is characterized by its short and craspedote scolex. The bothridia are separated, with free boarders. The tentacles are cylindrical, armed with solid and similar hooks in quincunxes.
Efficacy of praziquantel (Cesocide injection) by intramuscular (I.M.) route against cestode infections was evaluated. Total 93 domestic or laboratory animals such as dogs, cats, rats, mice, goats, deers and chickens were used. Animals were infected with Dipylidium caninum, Spirometra sp., Taenia pisiformis, Taenia taeniaeformis, Hymenolepis nana, Moniezia expansa, Moniezia sp. or Raillietina sp. A single dose of praziquantel, 6 mg/kg of body weight, was highly effective (97.9%) against cestodes of various kinds disregarding the host species or their intensity of infection. At high dose above 6 mg/kg, the cure rate was 100%. All the cestodes treated were expelled from the host within 48 hours. The discharged proglottids were damaged severely except Hymenolepis nana and Moniezia expansa. Intramuscular injection of this drug evoked a brief pain response in a dog, but no other side reactions were observed.
Large tumors removed from the lower abdomen and pleural cavity of a 24-year-old male Amerindian in Paraguay consisted mainly of multitudes of minute, proliferating, acephalic cestode larvae embedded in fibrous tissue. The parasite resembled Sparganum proliferum Stiles 1908 but was markedly less differentiated. From a review of the literature and examination of available reference material, it is concluded that in addition to the present one there are eight well documented cases of proliferating acephalic larval cestode infection in man: five in Japan and one in Florida (USA) that were S. proliferum, one in Pennsylvania (USA) that was an undifferentiated cysticercus or cysticercoid, and one in Taiwan that probably was an undifferentiated tetrathyridium. In four other cases the parasites are reclassified as being of doubtful nature in three and a racemose cysticercus in one. Review of the known species of proliferating cestode larvae naturally occurring in animals failed to identify possible sources of the acephalic forms observed in man.
The report contains the results of faunistic study of parasitic cestodes occurring in fishes in the S. Dvina, Mezen' and Pechora river basins. 26 cestode species have been recorded in the region explored. The cestode fauna in the first basin is represented by 19 species, in the second basin--14, in the third basin--18.