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PubMed2005

Epidemiological studies on equine cestodes in central Spain: infection pattern and population dynamics.

An epidemiological study on equine cestodosis was carried out in central Spain. A total of 372 digestive tracts from equids slaughtered in abattoirs located in central Spain were studied from November 2001 to May 2004. Anoplocephala perfoliata was detected in 24% of the animals and Anoplocephala magna in 18%. Individual tapeworm burden was from 1 to 491 tapeworms for A. perfoliata and from 1 to 64 tapeworms for A. magna. Low tapeworm burdens (less than 30 cestodes) predominated significantly (p<0.01) in all seasons for both species. Seasonal prevalence of infection by A. perfoliata was significantly higher (p<0.01) in autumn (37.5%) and winter (32.3%) than in spring (9.2%) and summer (10.8%). Immature tapeworms were detected throughout summer (11%), autumn (23.4%) and winter (26.6%), signalling a summer to winter risk period for tapeworm infection in our conditions. Mature non-gravid tapeworms were collected in all seasons, with a decreasing pattern from summer (89%) to spring (6.7%). Conversely, gravid tapeworms showed an increasing pattern, from 0 in summer to a maximum (93.3%) in spring. Since prevalence of infection was significantly higher in winter than in spring, winter seems to be the season when more eggs would be available to be eaten by mites. A. perfoliata infection was detected in three different periods throughout the 3 year study: autumn 2001-winter 2002, summer 2002-spring 2003 and autumn 2003-spring 2004. This epidemiological pattern seems to describe the dependence of A. perfoliata to humidity in warm dry climate. In our conditions, A. perfoliata appears to follow a pattern of having only one generation per year, with a marked dependence on humidity. According to the results, autumn rainfall would influence the length, and late spring rainfall the appearance, of each annual generation. A. magna showed a different pattern. Infection was detected throughout the whole study period. Seasonal prevalence was higher in autumn (25.5%) than in winter (14.9%), spring (12.1%) and summer (10.5%), but the differences were not statistically significant. Non-gravid A. magna tapeworms could be detected almost throughout the year but percentages were significantly higher (p<0.01) in autumn (50.2%), indicating recent ingestion, than in the other seasons (30% in summer, 12.8% in winter and 0% in spring). However, data from spring were not enough to discard the season as a risk period for A. magna infection.

Animals↗
PubMed2005

A modified critical test and its use in two dose titration trials to assess efficacy of praziquantel for Anoplocephala perfoliata in equids.

Aims of this study with 43 equids naturally infected with Anoplocephala perfoliata in two dose titration trials were to document (i) the usefulness of a critical test with a 48 h treatment to necropsy period, (ii) efficacy of an oral paste of 0.5-2.0 mg praziquantel/kg body weight, and (iii) when after treatment would fecal egg counts provide best estimates of the tapeworm's prevalence in a herd. All feces passed by an equid after treatment and collected in successive 12 h batches were examined for tapeworms. At necropsy, tapeworms were identified as attached to the mucosa or unattached. Tapeworms were examined with a stereoscope and identified as normal or abnormal. Fecal samples were taken for egg counts at treatment and at 6 h intervals thereafter. In 32 of 36 treated equids, efficacy was 100% and mean efficacies for 0.5, 1.0, 1.5 and 2.0 mg praziquantel/kg body weight were 85.5, 99.7, 100 and 100%, respectively. Two equids treated with 0.5 mg praziquantel/kg body weight had low efficacies (5.4 and 38.1%) and normal tapeworms were found attached in the ventral colon and in one equid also in the dorsal colon. In seven untreated equids, tapeworms were primarily in the cecum with 21.3% detached. "Major fragments" or worms without a scolex but otherwise nearly a complete worm were 20.5% of the number of intact worms; they were not included in the efficacy analysis but should be. If the two equids with low efficacy were eliminated and if the number of all tapeworms and major fragments are combined less than 0.5% were in feces within 12 h of treatment, about 20% were in the 12-24 h period, 42% in 24-36h, 24% in 36-48 h and 13.5% in the equids at necropsy. One horse passed all its tapeworms in 24 h. This 48 h test when compared with a 24 h one with no examination of feces was more efficient in use of trial animals and reduced underestimation and overestimation of efficacy. However, a protocol similar to the 48 h test but with a 24 or 36 h post-treatment period should be investigated. The mean egg count peaked 18-24 h after treatment and samples taken at that time would provide the best estimate of prevalence. The Cornell-Wisconsin centrifugal flotation technique had a specificity of 100% and at 18 and 24 h its sensitivity was 94%. A brief discussion on critical and controlled tests for assessing efficacy of an anthelmintic for A. perfoliata is presented.

Administration, Oral↗
PubMed1991

Epidemiologic study and control of Taenia solium infections with praziquantel in a rural village of Mexico.

This study reports the results of an epidemiologic survey for the detection of Taenia solium in a rural village of 559 inhabitants in Sinaloa, Mexico, as well as a large scale treatment of the population with praziquantel. The study was carried out in two stages. In stage 1, serial stool analysis of 392 persons detected a cluster of three T. solium tapeworms. A fourth T. solium tapeworm was detected through a household census, giving a 1.32% prevalence rate for this helminth. Over 70% of the population over five years of age was treated with a 10 mg/kg dose of praziquantel, and no additional tapeworms were found. Environmental studies for the detection of Taenia sp. eggs in soil, water, and and objects from the houses of tapeworm-infected individuals showed only one soil sample containing eggs compatible with Taenia sp. A total of 72 domestic pigs were examined for the presence of cysticerci under the tongue. One animal had cysts, and belonged to a household that had two T. solium tapeworm infections. Stage 2 of the study was carried out one year after large scale antihelminthic treatment (LSAT), and no infections with Taenia sp. eggs were found. No cysticercus-infected pigs were detected. Intestinal parasitosis decreased from 69.2% to 37.5%. It is concluded that LSAT with praziquantel is efficient in decreasing endemic foci of T. solium. Seropositivity to T. solium bladder fluid antigens was tested by enzyme-linked immunosorbent assay and found to be 11% before LSAT and 7% one year later. In family members living with T. solium tapeworm carriers, the number of seropositive individuals was 28%. The relative risk ratio of seropositivity for persons living in the same household with a T. solium tapeworm carrier was 2.95. Positive response was significantly higher in the 30-39-year-old age group, in which 30% were seropositive in stage 1, compared with 7% one year after LSAT. High seropositivity rates were significantly associated with tapeworm clusters as well as with individuals with a clinical history of seizures.

Adolescent↗
PubMed1986

Successful treatment of Diphyllobothrium latum and Taenia saginata infection by intraduodenal 'Gastrografin' injection.

Tapeworm infections are very difficult to cure completely. Thirteen patients with tapeworm infection, seven with Diphyllobothrium latum and six with Taenia saginata, were treated by the introduction of a radio-opaque contrast medium, 'Gastrografin', into the duodenum through a duodenal tube. The whole tapeworm with the scolex was expelled unfragmented within 1 h in eleven cases. One patient expelled a tapeworm 3 days after treatment; the peristalsis of his intestine had been severely disturbed after an attack of cerebral apoplexy. The tapeworm could not be expelled by the remaining patient, probably because she had severe intestinal adhesion. The injection of gastrografin allowed clear visualisation of the tapeworm, the diagnosis of the infection could be confirmed, and the descent of the tapeworm could be observed serially. This treatment had no serious adverse effects in any of out patients.

Adult↗
PubMed2004

A modified critical test for the efficacy of pyrantel pamoate for Anoplocephala perfoliata in equids.

Aims of this study with 13 equids naturally infected with Anoplocephala perfoliata were to document (i) a critical test with a period of 48 h from treatment to necropsy to assess the efficacy of an anthelmintic against the tapeworm, (ii) the efficacy of pyrantel pamoate oral paste at 13.2 mg pyrantel base/kg body weight, and (iii) the time after treatment when fecal egg counts would best estimate the tapeworm's prevalence in a herd. Feces passed in successive 12-h periods after treatment were examined for tapeworms. At necropsy, tapeworms in equids were identified as attached to the mucosa or unattached and, with a stereoscope, as normal or abnormal. At the time of treatment and at 6-h intervals thereafter, fecal samples were taken for egg counts. The efficacy of pyrantel pamoate was 96.6%; in 1 equid the efficacy was 75.3%, and in 8 it was 100%. "Major fragments" (worms without a scolex) accounted for 10% of the tapeworms recovered; they were not included in the efficacy analysis but should be. In 3 untreated equids necropsied, tapeworms were in the cecum, and 21.3% were detached. This protocol, when compared with a 24-h one without examination of feces, was more efficient in the treatment of trial animals and reduced underestimation and overestimation of an anthelmintic's efficacy. However, a protocol similar to this 48-h critical test but with a 24- or 36-h post-treatment period should be investigated. The mean egg count peaked 18 to 24 h after treatment and the samples taken at that time would provide the best estimate of prevelance of tapeworms in a herd. The Cornell-Wisconsin centrifugal flotation technique had a sensitivity and specificity of 100% at 18 h and 92% and 100%, respectively, at 24 h.

Animals↗
PubMed1999

Development of a serologic assay to detect Taenia solium taeniasis.

We developed a serologic assay to identify adult Taenia solium tapeworm carriers using excretory/secretory (TSES) antigens collected from in vitro cultured T. solium tapeworms. To identify taeniasis-specific antigens we used an immunoblot assay with serum samples from T. solium tapeworm carriers and cysticercosis patients. Antigens were identified that reacted with antibodies present in serum samples from taeniasis cases and not with those from cysticercosis patients. Using serum samples collected from persons with confirmed T. solium tapeworm infections, the test was determined to be 95% (69 of 73) sensitive. Serum samples (n = 193) from persons with other parasitic infections, including T. saginata tapeworm infections, do not contain cross-reacting antibodies to TSES, indicating that the assay is 100% specific. These data suggest that the immunoblot assay using TSES antigens can be used to identify persons with current or recent T. solium tapeworm infections and provides a new, important tool for epidemiologic purposes, including control and prevention strategies.

Adult↗
PubMed2003

Prevalence of antibodies to unique Taenia solium oncosphere antigens in taeniasis and human and porcine cysticercosis.

The presence of two oncosphere antigens (OAs) of 22.5 and 31.3 kD in whole and excretory/secretory (ES) OA preparations of both Taenia solium and T. saginata or in antigen preparations from T. solium metacestodes or immature tapeworms was assessed. This included an evaluation of whether antibodies to other cestodes cross-reacted to these OAs. The OAs were present in whole oncosphere extract and E/S antigens of T. solium, but were not present in other stages (immature tapeworm or metacestode) or in OAs of T. saginata. The majority (95%) of T. solium tapeworm carriers had antibodies to these OAs, while only 20% of active neurocysticercosis cases were positive. No antibodies to the OAs were found in healthy controls, subjects infected with Hymenolepis nana, patients with hydatid disease, T. saginata tapeworm carriers, hamsters infected with immature T. solium tapeworms, or dogs infected with Echinococcus granulosus. The OAs are stage and species specific to T. solium and antibodies to OAs are usually present in tapeworm carriers.

Adolescent↗
PubMed1997

Effect of tunicamycin on the uptake and incorporation of galactose in Hymenolepis diminuta.

The effects of tunicamycin (TM) on the uptake and incorporation of tritiated galactose into the tegumental membrane and carcass from adult Hymenolepis diminuta were examined to assess the potential usefulness of this inhibitor for studying the function of the tapeworm surface glycocalyx. Hymenolepis diminuta adults (11 days old) were preincubated for 1 hr, pulsed for 30 min with [3H]galactose and [14C]leucine, and chased for 2 hr; replicate experiments were conducted in which all media contained no TM or TM at 10 micrograms/ml. Tunicamycin significantly inhibited the incorporation of tritiated galactose into the tapeworm's carcass and 30,000-g tegumental membrane fraction. Incorporation of tritiated galactose into the tapeworm's tegumental surface membrane also was inhibited significantly when expressed relative to the incorporation of [14C]leucine. Tunicamycin did not affect the amounts of free, i.e., soluble, [3H]galactose or [14C]leucine recovered from the tapeworms not did it affect the short-term (2 min) uptake of [3H]galactose by tapeworms. Thus, the inhibitory effect of TM appears to be at the level of protein glycosylation rather than carbohydrate (galactose) transport. The data indicate that TM might be useful for producing tapeworm surface membranes with diminished carbohydrate moieties.

Analysis of Variance↗
PubMed2002

Kinetics of Taenia solium antibodies and antigens in experimental taeniosis.

Two groups of hamsters were infected with Taenia solium cysticerci, one of which was suppressed with methyl-prednisolone acetate on the day of infection and every 14 days thereafter. The other did not receive steroid treatment. Faecal and serum samples were taken prior to infection and then at weekly intervals. Parasite circulating- and coproantigens were detected by a capture ELISA with rabbit polyclonal antibodies against T. solium tapeworms. IgG antibodies in serum and in faecal supernatants were detected by ELISA with excretory-secretory products of T. solium adults recovered from hamsters. Infections remained up to 17 weeks in suppressed hamsters, but after week 11 no tapeworms were found in non-suppressed hosts. T. solium coproantigens in both groups of hamsters were positive from the 1st week post-infection (wpi) until the tapeworms were rejected. Circulating antigens were detected only in non-suppressed hamsters from the 3rd wpi until 1 week before T. solium was eliminated. All infected hamsters developed serum IgG antibodies against tapeworms which were detected from the 2nd wpi and decreased slowly after T. solium expulsion. Specific IgG in faecal supernatants was detected from the 3rd wpi only in non-suppressed hamsters. When suppression was stopped, coproantibodies could also be detected. The presence of IgG antibodies indicates that tapeworms induced an immune response in the experimental host and that when hamsters were suppressed with corticosteroids the immune response was impaired and did not allow the detection of IgG coproantibodies. This indicates, in addition, that the passage of T. solium antigens from the small intestine to the circulation was blocked.

Animals↗
PubMed1996

Use of excretory/secretory antigens for the serodiagnosis of Anoplocephala perfoliata cestodosis.

Whole worm extract (WWE) and excretory/secretory (E/S) antigens of Anoplocephala perfoliata were characterised by SDS-PAGE and their use in the serodiagnosis of equine cestodosis was evaluated. An enzyme-linked immunosorbent assay (ELISA) was used to compare WWE and E/S antigen as the capture layer in an antibody capture ELISA. E/S antigen gave the best differentiation between sera from tapeworm-positive and tapeworm-negative horses. The E/S-ELISA was optimised and validated against sera from horses of known tapeworm status. This assay gave a diagnostic sensitivity of 68% (n = 38) and a specificity in helminth-naive horses of 95% (n = 20). Western blot analysis of tapeworm-positive and tapeworm-negative sera revealed the immunoreactive proteins of E/S antigen to be those of 12 and 13 kDa.

Animals↗
PubMed2004

Amplification of ribosomal DNA of Anoplocephalidae: Anoplocephala perfoliata diagnosis by PCR as a possible alternative to coprological methods.

The diagnosis of tapeworm infections in horses relies on copro-diagnostic methods, which are time-consuming and of limited sensitivity for determination of the exact prevalence. The development of serological tests has slightly improved the detection of tapeworm infections, but more sensitive methods are still required. A polymerase chain reaction (PCR)-based approach may constitute a valuable tool to improve tapeworm diagnosis. Nuclear ribosomal DNA (rDNA) is a useful target for species and/or strain markers. Partial 18S, the internal transcribed spacer 1 (ITS-1), the 5.8S, the internal transcribed spacer 2 (ITS-2), and partial 28S rDNA of the equine tapeworms Anoplocephala perfoliata and Anoplocephaloides mamillana were amplified and sequenced. The lengths and GC contents of the regions sequenced were 2087-2091bp and 49.35-49.69% for A. perfoliata, and 2110-2119bp and 49.15-49.32% for A. mamillana, respectively. Sequence alignment and comparison of both taxa showed 79.3-80.2% identity. The lowest identities were found in the ITS regions with 39.9-43.5% for the ITS-1 and 59.5-61.2% for the ITS-2. No matches of the ITS-2 of A. perfoliata and A. mamillana were found with other species by BLAST search. For this reason, ITS-2 sequences seemed appropriate as accurate species markers and A. perfoliata ITS-2 primers were developed. The ITS-2 PCR enabled the detection of genomic DNA as low as 0.5 pgs. First efforts on the practical application of the PCR-based approach were made. A 6-mg fragment of a tapeworm proglottid was detected in 0.5 and 1g of faeces.

Animals↗
PubMed1999

Eradication of Taenia solium cysticercosis: a role for vaccination of pigs.

Neurocysticercosis due to Taenia solium is an important cause of human morbidity and mortality, particularly in Latin America and parts of Africa and Asia. The disease has been recognised as potentially eradicable. Emphasis has been placed on control of the parasite through mass chemotherapy of human populations to remove tapeworm carriers. This strategy does not control the source of tapeworm infections, cysticercosis in pigs, and parasite transmission may continue due to incomplete chemotherapy coverage of human tapeworm carriers or because of immigration of tapeworm carriers into control areas. Exceptionally effective, practical vaccines have been developed against cysticercosis in sheep and cattle and a recent trial has proved recombinant antigens to be effective against Taenia solium cysticercosis in pigs. A new strategy for eradication of Taenia solium is proposed, based principally on a combined approach of chemotherapy of human tapeworm carriers and vaccination of all pigs at risk of infection.

Animals↗
PubMed1999

Immunology and biochemistry of Hymenolepis diminuta.

This review is an account of modern research into the immunology and biochemistry of the rat tapeworm, Hymenolepis diminuta. The first half of the review is devoted to the immunological responses of the host to the parasite. It describes the specific responses that occur when the host is exposed to a primary infection, and the changes that occur when further infections are superimposed on the primary one. The aquisition of immunity to the tapeworm and its persistence in the absence of the infection are also discussed, as well as the non-specific responses of the host to the parasite. The second half of the review is concerned with biochemistry, summarizing the early biochemical work that has been carried out on the tapeworm and describing the metabolic pathways now thought to be characteristic of the parasite. What little information that exists on intermediary metabolism in eggs and larvae is summarized here. Much of this section is concerned with the role of mitochondria in H. diminuta, especially the control of the critical branchpoint (PK/PEPCK), which partitions carbon into either the cytosol or the mitochondrion. The role of 5-hydroxytryptamine in controlling both worm behaviour and metabolism is discussed, followed by a brief look at some other effectors that may prove in the future to have great significance in regulating the parasite. Finally, there is a detailed consideration of strain variation within H. diminuta and of the impact on the tapeworm of components of the immune system, formerly described as the 'crowding effect'. The review concludes with a brief discussion of evolutionary aspects of the rat-tapeworm relationship and a comprehensive bibliography.

Animals↗
PubMed2003

Sex, parasites and resistance--an evolutionary approach.

Immune systems are among the most diverse biological systems. An evolutionary arms race between hosts and rapidly evolving pathogens is supposed to be a reason for this diversity, and might explain why most eukaryotic hosts and parasites reproduce sexually. In this review, I will focus on possible benefits of sexual reproduction in hosts and parasites, using a model system consisting of a tapeworm and its two intermediate hosts, copepods and sticklebacks. We found that the hermaphroditic tapeworms can increase their infection success by reproducing sexually with a partner (outcrossing), instead of reproducing alone. The defence system of the copepods provides highly specific discrimination of antigenic characteristics of the tapeworms. This supports the finding that tapeworms benefit from outcrossing, but contradicts the conventional notion that the immune system of invertebrates, in contrast to vertebrates, is not able to react with specificity. Finally, sticklebacks seem to benefit from optimal diversity in their specific immune system. Previous studies showed that female sticklebacks prefer mates, which sire offspring with an optimal diversity in the MHC (genes involved in antigen presentation). We now found that these individuals suffer less from tapeworm infection. Furthermore, they are able to reduce the expression of an unspecific immune trait, thereby possibly avoiding harmful side effects of a highly activated, unspecific immune system.

Journal Article↗
PubMed2004

Life-history studies on two molecular strains of mesocestoides (Cestoda: Mesocestoididae): identification of sylvatic hosts and infectivity of immature life stages.

Life-cycle studies were conducted on 2 molecular strains of Mesocestoides tapeworms that represent different evolutionary lineages (clades A and B). Wild carnivores, reptiles, and rodents were examined for tapeworm infections at 2 enzootic sites: (1) San Miguel Island (SMI), a small island off the coast of southern California and (2) Hopland Research and Extension Center (HREC), a field station in northern California. Results indicate that deer mice (Peromyscus maniculatus) and coyotes (Canis latrans) may play an important role in the life cycles of Mesocestoides (clades A and B) in California. Over half the coyotes at HREC and at least a third of the population of island fox (Urocyon littoralis) at SMI were found to harbor clade A adult Mesocestoides spp. One of every 4 Mesocestoides-infected coyotes had tapeworms representing both clades A and B. Experimental inoculations revealed that proglottids (clades A and B) were not directly infectious to rodents, reptiles, or dogs. On the other hand, mice, lizards, and hamsters fed tetrathyridia of Mesocestoides spp. (clades A or B) developed peritoneal tetrathyridial infections. A dog that was fed tetrathyridia (clade B) developed an adult tapeworm infection. Acephalic metacestodes given orally to western fence lizards, laboratory mice, or domestic dogs did not result in metacestode or adult tapeworm infections. Whereas most clade A acephalic metacestodes from dogs were asexually proliferative, clade A tetrathyridia isolated from wild deer mice did not show evidence of asexual replication. Our study supports the hypothesis that a second, as of yet unidentified, intermediate host is necessary to complete the life cycles of Mesocestoides spp., and that acephalic metacestodes represent an aberrant form, incapable of further development.

Animals↗
PubMed2005

Taeniasis and cysticercosis in housemaids working in affluent neighborhoods in Lima, Peru.

Taenia solium taeniasis/cysticercosis is endemic in most developing countries, where it is an important cause of epileptic seizures and other neurologic symptoms. In industrialized countries, cysticercosis results from travel or immigration of tapeworm carriers from endemic areas. In both endemic and nonendemic countries, housemaids commonly immigrate from cysticercosis-endemic areas and can transmit the infection if they carry the adult tapeworm. Between July 2001 and July 2002, 1,178 housemaids (961 of them work in the top five most affluent districts of Lima, a metropolis of 8 million inhabitants considered nonendemic for cysticercosis) were evaluated for serum antibodies to Taenia solium and stool microscopy for taeniasis and cysticercosis. The serosurvey revealed a prevalence of cysticercosis-specific antibodies of 14.6% (95% CI: 12.6-16.6%), and stool microscopy detected 12 T. solium tapeworm carriers, for a prevalence of taeniasis of 1.2% (95% CI: 0.6-1.8%). A nonrandom sample of 26 seropositive housemaids was examined by brain CT and 50% of them had brain lesions compatible with neurocysticercosis, mainly calcifications. From the families who used a tapeworm-carrier housemaid, cysticercosis antibodies were detected in 6 (23%) of 26 persons who agreed to participate. One seropositive member of the employer families was symptomatic for seizures and had brain calcifications. The prevalence of tapeworm infections in this housemaid group is similar to levels in endemic areas, constituting a source of neurocysticercosis infection.

Adolescent↗
PubMed1997

Phylogeny of the orders of the Eucestoda (Cercomeromorphae) based on comparative morphology: historical perspectives and a new working hypothesis.

The phylogeny of the Eucestoda was evaluated based on a suite of 49 binary and multistate characters derived from comparative morphological and ontogenetic studies; attributes of adult and larval tapeworms were considered. A single most parsimonious tree (MPT) (consistency index = 0.872; retention index = 0.838; and homoplasy index = 0.527) was fully resolved and is specified by the following: (Gyrocotylidea, (Amphilinidea, ((Spathebothriidea, (Pseudophyllidea, ((Diphyllidea, (Trypanorhyncha, (Tetraphyllidea, (Lecanicephalidea, ((Nippotaeniidea, (Tetrabothriidea, Cyclophyllidea)), Proteocephalidea))))), Haplobothriidea))), Caryophyllidea))). Monophyly for the Eucestoda was firmly corroborated. Trees derived from the primary and bootstrap analyses were congruent, but low values, particularly for relationships among the tetrafossate tapeworms, indicated additional examination is warranted. The MPT was found to be the most efficient hypothesis for describing character evolution and in specifying relationships among the orders when compared to those concepts that had been developed for the tapeworms over the past century. Areas of congruence were shared among the current hypothesis and one or more of the prior hypotheses. Major conclusions include: (1) Caryophyllidea are basal and monozooy is ancestral; (2) difossate forms are primitive, and the Pseudophyllidea are the sister group of the strongly polyzoic tapeworms; (3) Nippotaeniidea are highly derived; (4) the higher tapeworms (Tetraphyllidea, Lecanicephalidea, Proteocephalidea, Nippotaeniidea, Tetrabothriidea, and Cyclophyllidea) are closely related or potentially coordinate groups: (5) Tetrabothriidea and the Cyclophyllidea are sister groups; and (6) Tetraphyllidea is paraphyletic, with the Onchobothriidae basal to the Phyllobothriidae. Character support for placement of the Tetrabothriidea continues to be contradictory, and this order may represent a key to understanding the phylogeny of the higher cestodes. The current study constitutes a complete historical review and poses a new and robust hypothesis for the phylogeny of the Eucestoda.

Animals↗
PubMed1992

The effect of dimethylsulfoxide on the tegumental brush border of the cestode Hymenolepis diminuta.

Dimethyl sulfoxide (DMSO), commonly used for cryoprotection or for the solvation of cytoskeleton-modifying drugs, causes changes in the topology of the plasma membrane of the tegumental brush border in the tapeworm Hymenolepis diminuta; however, relatively long exposures of high concentrations are required. In tapeworms treated with DMSO concentrations of greater than or equal to 1% in the present study, the interaction of the tegumental surface membrane with the underlying cytoskeleton may have been disrupted at focal points in the brush border, resulting in a partial loss of the membrane anchoring required for the structural integrity of the brush border. Blebbing of the tegumental surface was prominent only after exposure to 1% DMSO for 20 h in in vitro culture with RPMI 1640, and vesiculation of the membrane along the microvillar (microtriche) shafts, which may have been related to the in vitro conditions, was amplified by the presence of concentrations of greater than or equal to 1% DMSO in the incubation medium. The tegumental response to DMSO was not uniform but regional, consistently appearing to be more prevalent on the distal aspects of each proglottid rather than on the edge proximal to the scolex. Blebbing and vesiculation were not seen on the basal aspect of the tegument, including the basal ectocytoplasmic plasma membrane, the perikarya, and the internuncial processes. Microvillar core bundles of actin microfilaments persisted following 8 h in vitro exposure to all three concentrations of DMSO tested (0.1%, 1%, 5%); however, only in tapeworms that were treated in vitro with 5% DMSO for greater than or equal to 8 h did core microfilament bundles appear to lose the rigidly straight and parallel organization characteristic of control tapeworms that were incubated either in the absence of DMSO or with 0.1% DMSO. Other components of the brush border cytoskeleton (i.e., microvillar caps, junctional tubules, and tunics) appeared unaffected by DMSO except at foci where blebbing occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗