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PubMed1999

Ultrastructural study of the papillae and presumed sensory receptors in the scolex of the Gymnorhynchus gigas plerocercoid (Cestoda: Trypanorhyncha).

The ultrastructure of the papillae and presumed sensory receptors in the tegument of the scolex of Gymnorhynchus gigas plerocercoid were investigated by scanning and transmission electron microscopy. Four distinct types of putative sense receptor (including three uniciliated and one nonciliated) are described for the first time in G. gigas, and this investigation is the first detailed ultrastructure study of tegumental receptors carried out in trypanorhynch cestodes. Microtriches arranged in clusters with a dome-shaped pattern seemed to be papillae that contained a ciliated sensory receptor (type I). The density of these papillae was greater in the center of the bothridial adherent surface near the tentacle orifice than in the lateral margins of the bothridia or in the pars post-bothridialis. The type I receptor is characterized by a long cilium anchored in the nerve bulb by a dense basal body but lacks rootlets. The bulb contains one or two electron-dense collars, numerous electron-lucent neurovesicles, and some mitochondria. The type II receptor presents a short cilium retracted into an invagination of the tegument that arises from the basal body. The bulb contains one electron-dense collar and numerous electron-lucent vesicles, but the rootlets are absent. The type III receptor is also a ciliated receptor embedded in a bulb wider than that of types I and II, and it differs from type II in that it possesses two electron-dense collars and small rootlets associated with the basal body. No electron-lucent vesicle was found in the bulb of this type III receptor. The type IV receptor is a nonciliated receptor localized under the surface with no contact to the outside. It consists of a flattened bulb that contains two electron-dense collars and striated rootlets associated with a band of microfilaments. A comparison of the ultrastructural features of receptors in different cestodes is presented.

Animals↗

PubMed2004

The relationship between specialization and local abundance: the case of helminth parasites of birds.

Positive relationships are commonly observed between the abundance of a species in a locality and the frequency of its occurrence among localities on a larger scale. This pattern may not hold for parasitic organisms when the average abundance of a parasite among its hosts is related to the number of host species in which it occurs, because of the additive investment in specific adaptations to counter host immune responses required for each host species in a parasite's repertoire. For a rigorous test of the hypothesis that there is a trade-off between the number of host species that can be successfully exploited and the average abundance of parasites in those hosts, one needs to take into account the phylogenetic (or taxonomic) distances among the host species used by a parasite. Differences in immune responses are likely to increase with increasing phylogenetic distances. The trade-off hypothesis was tested in a comparative analysis of 393 species of trematodes, cestodes and nematodes parasitic in birds surveyed from the same geographical area, using an index of host specificity that measures the average taxonomic distances between a parasite's known host species. After correcting for the influences of parasite phylogeny and other potential confounding variables, mean abundance was negatively correlated with the average taxonomic distance among host species for nematodes, and with the variance in taxonomic distances among hosts for cestodes. In the case of trematodes, these variables covaried positively. The trade-off between average infection success and how taxonomically distant a parasite's host species are from each other was only found in two of the three groups of helminths investigated, possibly because of compensating features in trematodes, such as their ability to multiply asexually in intermediate hosts. These results provide empirical evidence consistent with the hypothesis that specialization allows greater local adaptation and therefore greater local population abundance, supporting key predictions regarding the evolution of ecological specialization.

Analysis of Variance↗

PubMed2006

Nomimoscolex pertierrae n. sp. (Eucestoda: Proteocephalidea), a parasite of Pseudoplatystoma corruscans (Siluriformes: Pimelodidae) in Brazil and redescription of N. sudobim Woodland, 1935, a parasite of P. fasciatum.

The cestode Nomimoscolex sudobim Woodland, 1935 (Proteocephalidea) is redescribed on the basis of its type-specimens and recently collected material found in the intestine of the 'sudobim' Pseudoplatystoma fasciatum (Siluriformes: Pimelodidae) (type-host), from the Amazon River (near the type-locality). Nomimoscolex pertierrae n. sp. is described from the 'surubi' Pseudoplatystoma corruscans from the Paraná River around Porto Rico. Among fifteen known Nomimoscolex species, only N. sudobim possess a cortical uterus in combination with osmoregulatory canals some distance internal to the proglottis margins, as in N. pertierrae n. sp. N. pertierrae differs from N. sudobim, which exhibits the most similarity with the former species, in the morphology of the scolex, the size and unusual shape of microtriches (slender digitiform) on the internal and marginal regions of the suckers, and in the lower mean number of testes [(114 in N. pertierrae, ranging between 216 (recently collected material) and 240 (type-material) in N. sudobim)]. The material described as N. sudobim by Pavanelli & Rego (1992) from the intestine of P. corruscans is considered to be N. pertierrae. The utility of microtriches as characters for distinguishing between species is demonstrated in the clear differences in the shape of those of N. pertierrae and N. sudobim. The morphology of microtriches warrants more attention in future studies on the taxonomy of proteocephalidean cestodes.

Animals↗

PubMed1983

Hymenolepis diminuta: effects of amoscanate on energy metabolism and ultrastructure.

Amoscanate possesses chemotherapeutic activity against schistosomes, and in higher doses against many other helminths including filariids and Hymenolepis diminuta. The primary mode of action of this compound is unknown. Effects of the drug on the carbohydrate metabolism as well as on the tegumental and nephridial epithelia of H. diminuta were examined. At various time intervals after administration of the drug to rats infected with H. diminuta, the parasites were recovered and incubated in glucose-salts medium for 90 min. Chemotherapy resulted in decreases in succinate, lactate, and acetate recoveries, while ATP levels dropped. In addition, glycogen levels were depressed in drug-treated worms which were homogenized immediately upon isolation. Glycogen synthase I activity was inhibited 16-61% in cestodes obtained from Amoscanate-treated animals and homogenized immediately, but returned to normal levels after incubation for 90 min in glucose-salts medium prior to homogenization and assay. Phosphorylase a activity was found to be 25-30% higher in preparations of worms from drug-treated rats, which correlates with the rapid depletion of glycogen in parasites exposed to the drug. However, in contrast with glycogen synthase activity, the elevation of phosphorylase a activity in H. diminuta exposed to the drug was not readily reversible. Attempts to demonstrate activity of the drug in vitro by incubating intact cestodes directly with Amoscanate were unsuccessful. Thin sections of parasites obtained from Amoscanate-treated rats and examined by transmission electron microscopy revealed surface alterations of the tegument and nephridial canals. Alterations included bleb formation and erosion of microtriches from the tegument, as well as disappearance of microvilli from nephridial canals. However, these effects became manifest only after 4 or more hr exposure of the rat to the drug. Biochemical effects, on the other hand, were significant after 3 hr exposure.

Adenosine Triphosphate↗

PubMed1985

Hymenolepis citelli (Cestoda) and Nematospiroides dubius (Nematoda): interspecific interaction in mice.

In mice concurrently infected with Hymenolepis citelli and Nematospiroides dubius, survival of the tapeworm was prolonged, and there was an impairment of the efferent arm of the response to the cestode. The immunological rejection of a six cysticercoid primary H. citelli infection was delayed by the N. dubius infection. The growth of the cestode was poorer in concurrently infected mice, and this effect was rapid, being evident within 4 days of the N. dubius infection. Maximum biomass in the controls was reached on Day 20, whereas in the concurrently infected mice it was reached on Day 25. The induction of acquired immunity to homologous H. citelli infection was suppressed, although the expression of a secondary response against homologous challenge was not abrogated in doubly infected mice. The results are discussed with reference to the immunodepressive effects the nematode is known to have on heterologous antigenic stimulation.

Animals↗

PubMed1987

Taenia hydatigena: isolation of mitochondrial DNA, molecular cloning, and physical mitochondrial genome mapping.

Mitochondrial DNA was isolated from Taenia hydatigena, T. crassiceps, and Echinococcus granulosus using a cetyltrimethylammonium bromide precipitation technique. The technique is simple, rapid, reproducible, and does not require extensive high speed ultracentrifugation. The advantage of using mitochondrial DNA from taeniid cestodes for comparative restriction analysis was demonstrated. Mitochondrial DNA of T. hydatigena was isolated as covalently closed circular molecules. These were linearized by single digestion with BamHI and the molecular weight was estimated from the linear form of 17.6 kb. The mitochondrial DNA of T. hydatigena is therefore similar in size and structure to that of many other animal species. The entire mitochondrial genome was cloned into pBR322 in Escherichia coli and a restriction map of the recombinant molecule was constructed. The potential of using the cloned mitochondrial genome as a probe in speciation studies as well as for providing functional information on the role of the cestode mitochondrion is discussed.

Animals↗

PubMed1990

Relative distribution of glutathione transferase, glyoxalase I and glyoxalase II in helminths.

Glutathione transferase, glyoxalase I and glyoxalase II activities were not evenly distributed among the major helminth groups. Intestinal cestodes and digeneans had higher glutathione transferase activity than parasitic nematodes. High glyoxalase II activity was found in cestodes and digeneans but no glyoxalase I was detectable. Glyoxalase I and II were both detected in nematodes. These results are discussed in relation to the enzymes' suggested role in protection against secondary lipid peroxidation products.

Animals↗

PubMed1990

Selective distribution of sugars on the tegumental surface of adult Bothriocephalus gregarius (Cestoda: Pseudophyllidea).

Whole specimens and histological and semi-thin sections of Bothriocephalus gregarius adults were exposed to lectins to identify carbohydrates present in the tegument and parenchyma. The sugars N-acetyl glucosamine, N-acetyl galactosamine, galactose, glucose (or mannose) and fucose were detected in the cestode using eight lectins: WGA (Wheat germ agglutinin), HPA (Helix pomatia agglutinin), SBA (Soy bean agglutinin), PHA (Phaseolus vulgaris agglutinin), RCA60 and RCA120 (Ricinus communis toxin and agglutinin), ConA (Concanavalin agglutinin) and UEA-I (Ulex europaeus agglutinin). Combined use of these methodological approaches (whole specimens, paraffin and semi-thin sections) revealed the presence of a gradient in the distribution of most of the sugars over the tegument, with the highest concentrations on the strobila (as shown by most of the lectins). Other sugars were specific for the scolex or strobila (as shown by UEA-I or HPA, respectively). The ultrastructural study showed that the distribution of glycoconjugates was associated with the presence of specific tegumental coats. The significance of this selective distribution and its relevance to cestode physiology and host-parasite relationships are discussed.

Animals↗

PubMed1986

The clinical significance of gastrointestinal helminths--a review.

Gastrointestinal helminths (nematodes, trematodes and cestodes) constitute some of the most common and important infective agents of mankind and are responsible for much morbidity and some mortality. Whereas many symptoms and signs are confined to the intestine and less often the associated digestive organs, systemic manifestations are also numerous; this applies especially to indigenous populations of developing 'Third World' countries. Using a clinical classification these organisms can be broadly separated into those involving the small-intestine and those which have a colo-rectal distribution; of the former, a minority has been causally related to intestinal malabsorption. Clearly, however, not all gastrointestinal helminths are associated with disease and it is important to be able to separate these two groups; when present at high concentration and especially in infants and children some of the least pathogenic are not, however, entirely asymptomatic. Maintenance of a high 'index of suspicion' is necessary and this applied especially to 'western' populations in whom rapid and extensive travel to areas of the world with substandard sanitation and contaminated food and water supplies is now common; first evidence of infection in them may result from serious clinical complications. Recent advances have focussed on treatment, and especially the introduction of the benzimidazole compounds (especially albendazole) for nematode, and praziquantel for cestode, infections. Treatment of strongyloidiasis remains, however, unsatisfactory. Mass elimination of gastrointestinal helminths in developing 'Third World' countries remains a major challenge.

Adult↗

PubMed1988

Application of the avidin-biotin immunohistochemical method for the diagnosis of alveolar hydatid disease from tissue sections.

The avidin-biotin immunohistochemical (ABC) method was applied to the diagnosis of alveolar hydatid disease in patients from the hyperendemic region of western Alaska. The test was specific for larval cestodes of the genus Echinococcus, and exhibited high sensitivity. A negative reaction was obtained in all cases in which spontaneous death of the larval cestode had occurred. Results were inconsistent in sections of lesions from patients who had received long-term therapy with mebendazole, because of the persistence of antigens for a considerable time following the death of the parasite.

Animals↗

PubMedDate not supplied

Detection of serum antibodies in human Hymenolepis infection by enzyme immunoassay.

Although hymenolepiasis is the commonest cestode infection of man, there are no data available on the human immune response to this parasite. Thus, in order to determine if infection induces antibodies against Hymenolepis nana antigens, sera from 52 infected children were initially studied on Ouchterlony plates and then by enzyme-linked immunosorbent assay (ELISA), using a crude antigenic extract prepared from scolex and neck regions of adult worms. In addition, sera from persons with cysticercosis, taeniasis and other parasitoses, and normal human sera, were studied. Only one serum from the Hymenolepis group showed precipitin antibodies against H. nana antigen, while several were positive by ELISA. The sensitivity of the ELISA was 84.62% and its specificity was 100%. Very high cross-reactivity rates were obtained with taeniasis (70.6%) and cysticercosis (75%) sera. These results show that Hymenolepis infection in man induces a low but detectable humoral immune response. Although not useful for diagnostic purposes, this may be relevant to the serodiagnosis of other tissue cestode infections of man, since antibodies detected in serological tests used for the diagnosis of cysticercosis, and probably hydatidosis, could be induced by H. nana instead of Taenia solium or Echinococcus larvae.

Adolescent↗

PubMed1981

Succinate decarboxylation to propionate and the associated phosphorylation in Fasciola hepatica and Spirometra mansonoides.

The trematode, Fasciola hepatica, and the cestode, Spirometra mansonoides have been shown to be similar to the nematode Ascaris lumbricoides in that all three decarboxylate succinate to propionate plus CO2. Associated with this decarboxylation is an incorporation of 32Pi into organic phosphate. Both the decarboxylation and phosphorylation are markedly stimulated by the addition of propionyl-CoA, are dependent on coenzyme B12 and are inhibited by avidin. The trematode and cestode exhibit propionyl-CoA carboxylase, methylmalonyl-CoA mutase and acyl-CoA transferase activities in sonicated mitochondrial preparations. Data are consistent with the occurrence of a mitochondrial substrate level site for ATP generation which is coupled with the decarboxylation of succinate. In Fasciola preparations, acetyl-CoA stimulates the decarboxylation and phosphorylation to a considerably larger extent than propionyl-CoA, indicating the possibility that acetyl-CoA may serve physiologically in these reactions by donating the CoA moiety to succinate.

Acetyl Coenzyme A↗

PubMed1990

Use of benzimidazole chemotherapy in human helminthiases: indications and efficacy.

The past two decades have seen some remarkable developments in anthelmintic chemotherapy in clinical medicine. Whereas praziquantel has revolutionized the management of many cestode and trematode infections, Gordon Cook explains how the introduction of the benzimidazoles - most importantly thiabendazole, mebendazole and recently albendazole (flubendazole, cambendazole, ciclobendazole, and triclabendazole have also been used on a very limited scale) - has had a major impact upon the safe and effective management of several important intestinal and systemic nematode and, to a leser extent, cestode infections.

Journal Article↗

PubMed1988

Epizootiology of endoparasitic infections in pet dogs and cats presented to a veterinary teaching hospital.

Prevalences of, and risk factors associated with, protozoan and helminth parasite infections were determined for pet dogs and cats presented to the teaching hospital of the University of Pennsylvania School of Veterinary Medicine. Of 2294 canine fecal specimens, 34.8% were found to contain one or more kinds of parasite, consisting of: hookworms (14.4%); Trichuris vulpis (12.3%); Giardia (7.2%); ascarids (5.5%); coccidia (2.7%); cestodes (1.6%). The following risk factors were identified with infection in dogs: age less than 2 years; urban locality; male sex. Gonadectomy was associated with decreased parasite prevalences in both male and female dogs. Significant seasonal variations in prevalences of hookworm, ascarid and Giardia infections were found in dogs. Of 452 feline fecal specimens tested, 24.6% were positive for parasites, including: ascarids (16.4%); Giardia (3.5%); coccidia (2.9%); cestodes (2.4%); hookworm (1.1%). Host age of less than 2 years was a significant risk factor associated with parasitism in cats. Of 1571 dogs tested for Dirofilaria immitis microfilaremia, 3.7% were positive. Non-urban locality was a significant risk factor for D. immitis infection in dogs.

Age Factors↗

PubMed1989

The serological response of pigs experimentally infected with a species of Taenia from Taiwan.

An enzyme-linked immunosorbent assay (ELISA) for the detection of antibody in pigs infected with a possibly new species of Taenia isolated in Taiwan is described. The test antigen ThFAS was fractionated from the cyst fluid of a heterologous cestode Taenia hydatigena. In lightly infected pigs (less than or equal to 4 recovered cysts at necropsy 17 weeks post-inoculation), antibody was detected as early as 3 weeks post-inoculation. In more heavily infected pigs (6-72 recovered cysts at necropsy 32 weeks post-inoculation), antibody was still detectable at the time of necropsy. Cysticerci were found only in the livers of the infected pigs. This ELISA should be highly useful for detecting infection of pigs with this larval cestode in regions where the presence of Taenia solium is unlikely.

Animals↗

PubMed2005

Cadmium and lead concentrations in Skrjabinotaenia lobata (Cestoda: Catenotaeniidae) and in its host, Apodemus sylvaticus (Rodentia: Muridae) in the urban dumping site of Garraf (Spain).

The present study evaluates the parasitological model constituted by the wood mouse (Apodemus sylvaticus) and its intestinal cestode (Skrjabinotaenia lobata) as a potential bioindicator of Cd and Pb in the urban dumping site of Garraf near the city of Barcelona (Spain) and in Begues (reference site). Tissues and respective S. lobata specimens of 38 wood mice captured in Garraf and Begues were analyzed for Cd and Pb by means of ICP-MS. Higher cadmium levels in S. lobata were found only in respect to the muscular levels of their hosts. Nevertheless, lead levels were 8.5-, 53.2- and 81.4-fold higher in S. lobata than kidney, liver and muscle levels of A. sylvaticus from Garraf, respectively. Thus, the proposed model seems to be a promising bioindicator to evaluate environmental lead exposure in terrestrial habitats. In addition, all available data on lead bioaccumulation by cestode parasites of terrestrial mammals are generally discussed.

Animals↗

PubMed2006

Drug transport mechanisms in helminth parasites: passive diffusion of benzimidazole anthelmintics.

Anthelmintic molecules must reach their receptors inside target parasites to exert the pharmacological effect. Available data suggest that the main route of entry of antiparasitic drugs into helminth parasites would be through their external surface. However, it is unclear if trans-tegumental/cuticular penetration is the most important way of entry of benzimidazole (BZD) anthelmintics into their target parasites compared to oral ingestion. The relative involvement of active and passive transport mechanisms has not been defined. The goal of the work reported here was to determine the main processes involved in the entry of BZD anthelmintic molecules into the three main classes of helminth parasites. Adult specimens of Moniezia benedeni (cestode), Fasciola hepatica (trematode) and Ascaris suum (nematode) were incubated in Kreb's Ringer Tris buffer (pH 7.4, 37 degrees C) (1g parasite/10 ml incubation medium) for 15, 45, and 90 min, respectively, in the presence of a concentration gradient of either fenbendazole (FBZ), oxfendazole or triclabendazole sulphoxide (TCBZSO) (1-30 mol/ml, n=4). Dead helminth specimens were also incubated with the same drug concentration gradient. Specimens of F. hepatica with the oral route closed off by ligation were incubated with TCBZSO in the presence or absence of bovine serum albumin. After the incubation time elapsed, samples of parasite material were chemically extracted and prepared for high performance liquid chromatography analysis to measure drug/metabolite concentrations. Equivalent drug concentrations were measured within ligated and non-ligated liver flukes, demonstrating that BZD do mainly penetrate by trans-tegumental diffusion. The higher the concentration of BZD molecules in the incubation medium, the greater their concentration recovered within the helminth parasites. High correlation coefficients (>0.98) were obtained between initial drug concentration in the incubation medium and those measured inside the nematode, cestode, and trematode parasites. FBZ concentrations recovered from tissues of dead cestodes/nematodes over time were significantly greater compared to those measured in living parasites. These differences in drug diffusion may be related to the morphological/functional properties of the parasite's external surfaces. The outcome of the work reported here indicates that passive drug transfer through the external helminth surface is the main transport mechanism accounting for BZD accumulation into target parasites.

Animals↗

PubMed2006

Paraphyly of the Pseudophyllidea (Platyhelminthes: Cestoda): circumscription of monophyletic clades based on phylogenetic analysis of ribosomal RNA.

Phylogenetic relationships of cestodes of the order Pseudophyllidea (Platyhelminthes: Cestoda) were examined using sequences of complete small subunit and partial (D1-D3 region) large subunit nuclear rDNA of members of all pseudophyllidean families. The results provide evidence of paraphyly of the order as indicated by previous molecular phylogenetic analyses based on a much lower number of species sequenced. Pseudophyllidean tapeworms represent an artificial assemblage comprising two unrelated clades. "Bothriocephalidea" is formed by four families sensu Bray et al. (1994), namely Bothriocephalidae, Echinophallidae, Philobythiidae and Triaenophoridae, whereas two other families, Diphyllobothriidae and Cephalochlamydidae, give rise to the "Diphyllobothriidea". The present results indicate that "Bothriocephalidea" forms the most derived clade of all difossate and tetrafossate/bothriate tapeworm lineages which are considered to be basal relative to the rest of tetrafossate/bothridiate and acetabulate cestodes. By contrast, "Diphyllobothriidea", which includes medically important parasites (Diphyllobothrium and Spirometra), appeared more basal, without a clearly resolved position within other difossate tapeworm lineages.

Animals↗