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PubMed1995

Ultrastructure of the scolex and tentacles of the metacestode of Polypocephalus species (Cestoda: Lecanicephalidae) from the blue-swimmer crab Portunus pelagicus.

The ultrastructure and histochemistry of the scolex of a Polypocephalus species is described. This cestode is distinguishable from all known Polypocephalus spp. in that it has approximately 400 tentacles and inhabits the musculature of the blue swimmer crab, Portunus pelagicus. The metacestode has a large scolex, divided into an anterior par apicalis, and a posterior pars basalis. An elongate cercomer lies posteriorly to the scolex. The pars basalis lacks accessory suckers. The tegument of this region is armed with numerous spinous microtiches. The pars apicalis consists of approximately 400 unarmed tentacles, a large cavity ( = scolex cavity) containing some glandular tissue, and lying posteriorly to this cavity, a large gland ( = scolex gland). The tegument of the tentacles and pars apicalis is typically syncytial, and contains abundant electron-opaque secretory vesicles. These vesicles are produced by glandular tissue of the scolex gland and scolex cavity. Histochemistry revealed the presence of proteins and neutral mucosubstances in tentacles, scolex gland and scolex cavity, suggesting the presence of glycoproteins. It is argued that the secretion produced by the tentacles has an adhesive role. When applied to the large interface between the tentacles and the mucosa of the hosts, this secretion may provide the adult parasite with a strong holdfast to prevent dislodgement.

Animals↗
PubMed1992

A survey and review of hepatobiliary lesions in Australian macropods.

This report presents information on the range of diseases and lesions that occurred in sections of livers of macropods held in the Non-Domestic Animal Registry at Taronga Zoo. Of 142 affected livers, 52 were due to parasites, 24 to bacteria, nine to Macropod Herpesvirus, four to fungal agents and ten to tumours. In addition, 17 livers had acute degenerative or necrotic lesions, 22 were affected by fibrosis or other chronic lesions and four had miscellaneous degenerative lesions. Common parasitic diseases included toxoplasmosis, coccidial cholangitis, cestode cholangitis (Progamotaenia sp.), fascioliasis and capillarial hepatitis. Bacterial diseases were varied but lesions due to anaerobic bacteria or Mycobacteria spp. were most common. Many of the acute degenerative lesions were associated with cardio-respiratory disease. Chronic lesions were often of unknown origin, although it was speculated that parasitic and bacterial organisms contributed to the aetiology. There were four primary and six metastatic tumours.

Animals↗
PubMed1975

A comparison of post-mortem analysis of helminths with faecal egg counts.

Intestinal helminth infections are very common amongst residents of the Colombo area. Most common by post-mortem examination of 104 cases of sudden death were Trichuris trichiura (97.1%), Necator americanus (88.5%), Enterobius vermicularis (77.9%) and Ascaris lumbricoides (40.4%). Trematode and cestode infections were not encountered except a single case of H. diminuta infection. A comparison of the results obtained by the direct smear method for examining stools missed cases harbouring gravid females of up to 3 Ascaris lumbricoides, 29 Trichuris trichiura and 66 Necator americanus. The direct smear revealed all the helminths present except threadworms in only 30% of the cases. The correlation between worm loads calculated from ova counts and actual numbers harboured was fairly close in 19 out of 35 cases for Ascaris and 37 out of 78 cases for Necator americanus. Highly erroneous results were obtained in many instances when worm loads were calculated from the results of ova counts.

Adolescent↗
PubMed1983

Albendazole: placebo-controlled study in 870 patients with intestinal helminthiasis.

A total of 870 patients, both males and females, from 3 to 79 years old, received either albendazole or a placebo for the treatment of nematode and cestode infections. Each patient was interviewed and underwent a complete physical examination on the initial visit. In addition, complete blood count, clinical blood chemistry values and routine urinalysis were performed before and at least 24 hours after the last treatment. Stool examinations were performed before, 7 and 21 days after treatment. Direct examination, an egg count using the Kato technique and faecal concentration were carried out for each patient. In ancylostomiasis and strongyloidiasis, faeces were cultured by the Harada-Mori technique. Albendazole, as a single 400 mg oral dose, was highly effective against Ascaris lumbricoides, Necator americanus, Ancylostoma duodenale and Trichuris trichiura; efficacy against Strongyloides stercoralis was observed after three consecutive days of treatment at the same daily dose level. Efficacy against Hymenolepis nana was fair. Based on both clinical signs and biological values, albendazole did not produce any significant side effects.

Adolescent↗
PubMedDate not supplied

Single dose treatment with praziquantel for human Diphyllobothrium nihonkaiense infections.

Diphyllobothrium nihonkaiense is a large pseudophyllid cestode and one of the commonest parasites derived from fish in Japan. Three Japanese patients infected with D. nihonkaiense were treated with a single oral dose of 7, 23 or 25 mg/kg of praziquantel. All patients expelled the tapeworm with scolex, and no side effect was noted. This study indicates that single-dose treatment with praziquantel is effective against D. nihonkaiense infection.

Adult↗
PubMed1984

Expression of Taenia taeniaeformis antigens in Escherichia coli.

Two important features of infection of mice with larvae of Taenia taeniaeformis are the ready demonstration of host protective antibodies and the ability to immunize susceptible strains of mice against first infection using crude parasite preparations. Candidate immunogens in established larvae and the invasive oncosphere have been identified by immunoprecipitation of radiolabeled parasite proteins with host-protective antibodies. To overcome the difficulties associated with purification of these antigens from parasite material, the alternative strategy of expressing parasite proteins in Escherichia coli has been adopted. Double stranded DNA complementary to mRNA from 28 day old liver larvae was inserted into the beta-galactosidase gene of the bacteriophage lambda Amp 3. Some recombinants express a fusion protein with additional parasite-encoded epitopes located at the C-terminal end of the beta-galactosidase protein. Four clones that reacted with antibodies in an E. coli colony immunoassay were selected for detailed characterization. Analysis of lysates of the selected clones by SDS-PAGE and Western blotting revealed that each clone produced an abundant fusion protein that reacted specifically with a hyperimmune anti-oncosphere serum. Sibling analysis revealed that the four antiserum-positive clones encoded three immunologically-distinct parasite antigens. The identity of the native protein of larvae encoded by one clone (designated TA10) was an abundant antigen of Mr 70,000. This approach allows the assessment of antigens expressed in E. coli as vaccines in susceptible strains of mice by direct immunization and challenge and thus the development of a model defined-antigen vaccine against a larval cestode parasite.

Animals↗
PubMed1984

Evidence for a Ca2+-dependent activator protein in the rat tapeworm Hymenolepis diminuta.

A low molecular weight, acidic, heat stable protein has been characterised from the rat tapeworm Hymenolepis diminuta. This protein was found to activate cyclic 3', 5'-nucleotide phosphodiesterase in a Ca2+-dependent manner. The activation process was inhibited by the phenothiazine drug trifluoperazine. The biochemical properties of this protein clearly resemble those of ovine brain calmodulin. Our investigation thus concludes that there is a calmodulin-like activator protein in this cestode.

Amino Acids↗
PubMed1985

Stage and sex specific differences in actin gene expression in Schistosoma mansoni.

We have characterized actin gene expression in Schistosoma mansoni at the RNA and protein levels. Northern blot analyses showed two size classes of actin mRNA in eggs, cercariae and adult worms of both sexes, approximately 1 900 and 1 400 bases in length. A higher abundance of actin mRNA of both size classes was demonstrated in male worms than in eggs, cercariae, and females. Using a phalloidin-rhodamine conjugate, male worms were observed to contain more actin protein than females. Southern blot-hybridization indicated that the sexual differences in actin mRNA and protein levels were not related to some S. mansoni actin genes being sex linked. In addition, two other trematodes, Schistosoma japonicum and Fasciola hepatica and a cestode, Taenia pisiformis contained two classes of actin mRNA similar in size as those in S. mansoni. In contrast, a turbellarian, Dugesia tigrina contained only a single short actin message size class approximately 1 400 bases in length.

Actins↗
PubMed1987

Specific and cross-reactive antigens of Echinococcus granulosus hydatid cyst fluid.

The parasite antigens of Echinococcus granulosus hydatid cyst fluid have been characterised using the techniques of radioiodination, immunoprecipitation, SDS-PAGE, and immunoblotting. Five major subunit antigens of the parasite have been identified of relative molecular mass (Mr) 12,000, 16,000, two at 20,000, and 38,000 when reduced. The 12 and 16 kDa molecules are specific to E. granulosus and are excreted/secreted by both U.K. strains of the parasite and all human isolates examined, although not all hydatid disease patients produce antibodies to them. These molecules may be suitable for detection in specific immunodiagnosis. The 38 kDa molecule associates, via a disulphide linkage, with one of the 20 kDa molecules to form a single molecule of 60 kDa. This antigen is cross-reactive with human antibody to other cestode, trematode, and nematode parasites. Part of this cross-reactivity is associated with the presence of phosphorylcholine bound to the 38 kDa subunit.

Animals↗
PubMed1987

Effect of phenothiazines on Hymenolepis diminuta with special reference to the brush border Ca2+-dependent ATPase.

Incubation of Hymenolepis diminuta with the calmodulin antagonist trifluoperazine causes lesions in the brush border of the cestode. Exposure to a phenothiazine of lower lipophilicity, trifluoperazine sulphoxide, had little effect. Characterisation of isolated brush border revealed two forms of Ca2+-ATPase which exhibited maximum activity at pH 5.5 and 7.5. Both forms were Ca2+-dependent but only the latter was influenced by calmodulin and trifluoperazine. It is suggested that the Ca2+-ATPase present in the tapeworm brush border may be the site of trifluoperazine toxicity.

Animals↗
PubMed1991

Paramyosin is the Schistosoma mansoni (Trematoda) homologue of antigen B from Taenia solium (Cestoda).

Antigen B, a major antigen of the cestode parasite Taenia solium, has been purified and a portion of amino acid sequence obtained. Paramyosin of the trematode parasite Schistosoma mansoni, an immunogenic protein that has shown promise as a vaccine candidate, has several biochemical and immunological properties in common with antigen B. A full-length cDNA clone of S. mansoni paramyosin has been obtained and the predicted translation product contains a sequence that is highly homologous to the sequence obtained for antigen B. The predicted amino acid composition and isolectric point of paramyosin are nearly identical to those established for antigen B. Recombinant S. mansoni paramyosin, expressed in Escherichia coli as a fusion protein with beta-galactosidase, was recognized by antisera against T. solium antigen B. We conclude from these results that S. mansoni paramyosin and T. solium antigen B are homologous proteins. Since S. mansoni paramyosin is thought to be a muscle protein and T. solium antigen B a secreted glycoprotein with anti-complement activity, this conclusion raises some interesting questions regarding the role of this class of proteins in the host-parasite relationship.

Amino Acid Sequence↗
PubMed1993

Molecular cloning of an echinococcal microtrichal antigen immunoreactive in Echinococcus multilocularis disease.

A cDNA expression library of the larval stage of the cestode worm Echinococcus multilocularis has been established in the phage lambda ZAPII system. By immunoscreening with pooled sera from patients with alveolar echinococcosis an immunoreactive clone, termed pEM13, was isolated. EM13 was expressed using the expression vector pGEX-3X, resulting in the synthesis of a glutathione S-transferase fusion protein. 82% of the sera from 28 patients suffering from E. multilocularis disease had antibodies against EM13, whereas none of the 55 sera obtained from Echinococcus granulosus-infected patients and none of the 15 sera from patients with other helminthic infections reacted with recombinant EM13. By use of a polyclonal rabbit anti-EM13 hyperimmune serum native EM13 protein could be detected only in the protoscolices of E. multilocularis, but not in E. granulosus larvae or hydatid fluid. Immunoelectron microscopy suggested that EM13 is located in the microtriches on the surface of the larvae. In contrast, EM13 mRNA could be detected by Northern blot analysis in both E. multilocularis and E. granulosus larval RNA preparations. Nucleotide and amino acid sequence analysis of a cDNA clone coding for the corresponding antigen of E. granulosus larvae, termed EG13, revealed a 21-bp insertion, a 51-bp deletion and additional 22 nucleotide exchanges resulting in a 96.3% identity at the nucleotide sequence level and a 96.6% identity at the amino acid sequence level to the coding region of the cDNA pEM13. Cross-reactivity of the polyclonal anti-EM13 serum with the recombinant EG13 indicates a posttranscriptional regulation mechanism, resulting in an EG13 negative phenotype in E. granulosus.

Amino Acid Sequence↗
PubMed1996

Molecular cloning, expression and characterization of a recombinant glutathione S-transferase from Echinococcus multilocularis.

We report the identification and characterization of the first cestode glutathione S-transferase (GST) cDNA sequence. A fragment of an Echinococcus multilocularis glutathione S-transferase cDNA was isolated by the polymerase chain reaction. Subsequently, a Lambda zap cDNA library prepared from mRNA from protoscolices of E. multilocularis was screened with this PCR fragment. A complete cDNA clone was isolated and the nucleotide sequence determined. Analysis of the E. multilocularis GST-deduced amino acid sequence indicates that it is clearly related to the mammalian mu-class GSTs. The E. multilocularis GST cDNA was expressed in Escherichia coli, using a protocol designed to produce the native enzyme rather than a fusion protein. The 25.5-kDa enzyme subunit was purified to homogeneity using glutathione-sepharose chromatography. Gel filtration demonstrated that this GST is enzymatically active as a homodimer. The recombinant enzyme had conjugating activity with organic hydroperoxides and with members of the trans,trans-2,4 alkadienal and trans-2-alkenal series, which are secondary products of lipid peroxidation.

Amino Acid Sequence↗
PubMed1986

Hydatidosis: changing concepts in epidemiology and speciation.

Hydatidosis, caused by dog tapeworms of the genus Echinococcus, is one of the most important cestode infections of man. It is widely distributed and recent information points to a spread of the disease into areas previously free of it. This article reviews recent advances in understanding the biology of Echinococcus, relating these developments to the epidemiology of hydatid disease and its control.

Journal Article↗
PubMed1988

Clinical use of praziquantel in China.

Praziquantel, a broad-spectrum anthelmintic developed by E. Merck and Bayer AG in Germany in the early 1970s, was synthesized in the People's Republic of China in 1977 and given the Chinese name Pyquiton. After a series of pharmacological and toxicological studies in China, praziquantel was released for clinical use in 1978. The drug is now available for treatment of human schistosome and other trematode infections as well as the treatment of cestode infections including cysticercosis. However, much of the clinical work has been published in Chinese journals that may not be universally familiar. This article summarizes some of the key aspects of these reports, dealing with the clinical use of praziquantel against schistosomiasis japonica and other helminth infections in China.

Journal Article↗
PubMed1992

Praziquantel: The enigmatic antiparasitic.

Praziquantel (PZQ), a pyrazinoisoquinoline, was introduced as a novel anthelmintic in 1975. PZQ is currently the drug of choice for the treatment of a wide range of both veterinary and human trematode and cestode infections, including human schistosomiasis. Current estimates suggest that 150 million humans are infected with schistosomes, and it is expected that PZQ will play the lead role in chemotherapeutic control of those infections. Despite the time that has passed since its introduction and its obvious importance in global health care, it is not yet understood why PZQ is so selective and effective. The target molecules for PZQ have not been defined, nor are the sites of its effects within the parasites known. Here, Tim Day, James Bennett and Ralph Pax summarize some of the progress that has been made toward reaching these objectives in recent years.

Journal Article↗
PubMed1992

Interbreeding, monophyly and the genetic yardstick: species concepts in parasites.

The biological species concept defines species on the criterion of interbreeding. This may not be applicable to many parasites that are capable of self-fertilization and asexual reproduction. In this review, Alan Lymbery explores alternative concepts that may be applied to recognize species in such groups, using the cestode genus Echinococcus as an example. Two conclusions can be drawn. First, that the applicability of the biological species concept should not be dismissed without some knowledge o f the frequency of interbreeding in natural populations. Second, that where interbreeding is absent or rare, species should be delimited on the basis o f both monophyletic origin and genetic distinctness.

Journal Article↗
PubMed1996

Evolutionary biology of parasitic platyhelminths: The role of molecular phylogenetics.

As our appreciation of the diversity within the flatworms has grown, so too has our curiosity about the ways in which these varied creatures are related to one another. In particular, the parasitic groups (trematodes, cestodes and monogeneans have been the focus of enquiry. Until recently, morphology, anatomy and life histories have provided the raw data for building hypotheses on relationships. Now, ultrastructural evidence, and most recently, molecular data from nucleic acid sequences, have been brought to bear on the topic. Here, David Blair, Andrés Campos, Michael Cummings and Juan Pedro Laclette discuss the ways in which molecular data, in particular, are helping us recognize the various lineages of flatworms.

Journal Article↗