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Putative neurosecretory cells were observed with the electron microscope in the nerve cords of the neck region of Hymenolepis microstoma. The cells show evidence of glandular activity by the large numbers of dense-core vesicles produced by the Golgi apparatus. The axons contain synaptoidlike structures with surrounding clouds of vesicles; features analogous to known neurosecretory release sites.
Clinical field trials were conducted at five geographical locations in the USA (Oklahoma, Wisconsin, Tennessee, Virginia and Idaho) to evaluate the efficacy and safety of pyrantel pamoate paste (19.13%, w/w, pyrantel base) administered at the recommended dosage of 13.2 mg pyrantel base/kg (6.0 mg pyrantel base/lb) body weight (b.w.) against tapeworm infections of Anoplocephala spp. in naturally infected horses. Horses at each study site were allocated by restricted randomization based on the cestode status (positive or negative) of pre-treatment fecal egg counts to complete sets of four animals each or incomplete sets of fewer than four animals. Within sets comprising of two to four horses, one animal was randomly allocated to receive placebo vehicle paste and the remaining horse(s) received pyrantel pamoate paste administered orally at a minimum dosage of 13.2 mg pyrantel base/kg b.w. on Test Day (TD) 0. Single animal sets received pyrantel pamoate paste. Fecal samples of horses were collected and examined for equine tapeworm (Anoplocephala spp.) eggs a minimum of four times (once or thrice between TD -28 and -14, twice between TD -14 and -7, and once on TD 0) prior to treatment on TD 0. Fecal samples of horses that were positive for cestode infection pre-treatment were examined for cestode eggs on TD 7, 8, 9, 14, 15 and 16. Cestode-negative pre-treatment horses were not sampled again after treatment. A total of 241 horses (141 mares, 16 stallions and 84 geldings; 6 months-30 yrs of age; 173-646 kg; 13 recognized breeds and various crossbreds) were evaluated. The prevalence of Anoplocephala spp. determined by pre-treatment fecal examination ranged from 38.3% in Idaho to 68.1% in Tennessee with an overall prevalence of 52.3%. Ninety cestode-positive and 88 cestode-negative horses were treated with pyrantel pamoate paste, 36 cestode-positive and 27 cestode-negative horses were treated with placebo vehicle paste. Overall, 178 horses were treated with pyrantel pamoate paste, and 63 horses were treated with placebo paste. Of the 178 horses treated with pyrantel pamoate paste, no drug related, adverse clinical or neurological health events were observed. No doses of pyrantel pamoate paste were refused or lost during dosing. At each post-treatment time sampling interval, significantly fewer cestode eggs (P < 0.0115) were passed by cestode-positive horses treated with pyrantel pamoate paste compared to cestode-positive horses that received placebo paste. Efficacy of the pyrantel pamoate paste treatment ranged from 92 to 96% from TD 7 to TD 16 with an overall efficacy of 95%. The results of these trials demonstrated that pyrantel pamoate paste (19.13%, w/w, pyrantel base) administered orally at a dosage of 13.2 mg pyrantel base/kg b.w. is highly efficacious (95%) against Anoplocephala spp. and safe for use in horses with no adverse clinical or neurological health events observed under field use conditions.
Little is known about the cestode parasites of red grouse Lagopus lagopus scoticus. The carcasses of 71 free-living and grouse collected from northeastern Scotland (UK) between June 1991 and September 1992 were examined for the cestode Paroniella urogalli. Over 70% of young and old birds were infected in summer and winter. Cestode abundance ranged from 0 to 29 (mean +/- SE = 5.54 +/- 0.81) worms per host and did not differ significantly between young and old grouse, or between seasons. Cestode intensities did vary significantly between the sexes, but in opposite directions at two sites. A significantly greater total biomass (dry weight) of cestodes was found in grouse in the summer. Cestode biomass also was greater in young than in old grouse, although there was no significant difference after controlling for the effects of site, year and season. However, in the summer total cestode biomass in young grouse was significantly greater per unit bodyweight than in old grouse. No evidence was found for an effect of cestodiasis on grouse condition but a significant positive correlation existed between grouse comb condition and cestode abundance. Estimates of mean per capita worm mass suggested an intensity dependent reduction in the weight of individual cestodes in birds in their first summer. Per capita cestode mass was significantly lower in winter than summer, which may suggest that the production of mature proglottids varies with season. There was also a significant negative correlation between numbers of the nematode Trichostrongylus tenuis and the total biomass of P. urogalli in grouse.
We tested the hypothesis that the cestode Schistocephalus solidus is capable of premature gamete exchange as a plerocercoid in the last intermediate stickleback host. The existence of such a reproductive mode is suggested by the highly advanced gonadal development in the plerocercoid and the large fitness gain of outcrossing. In addition, eggs from selfing cestodes have a higher hatching rate when the cestode originated from a doubly infected stickleback than when it came from a singly infected fish. We hatched eggs from 10 singly breeding cestodes that originated from doubly infected sticklebacks with the prediction that some should be outcrossed and share alleles with both the breeding cestode and the second cestode in the coinfection if the hypothesis is correct. However, all of the 430 tested larvae matched only the alleles of the breeding cestode. It is therefore very unlikely that S. solidus engaged in gamete exchange in its fish host. We suggest an alternative hypothesis to explain the higher hatching rate of eggs produced by cestodes from doubly infected fish as compared to those from single infections.
The life cycle of marine Eubothrium sp. (Cestoda: Pseudophyllidea), from Atlantic salmon (Salmo salar L.) was experimentally completed in one year and included only one intermediate host (Acartia tonsa Dana) (Copepoda: Calanoida). Adult cestodes were collected from farmed salmon, and ripe eggs released by the cestodes were fed to Acartia tonsa. Ingested eggs hatched in the gut and the larvae developed in the haemocoel of the copepod for 15 days at 16 degrees C. A total of 170 seawater-reared salmon were exposed to infected copepods and the total prevalence of Eubothrium sp. in the salmon after infection was 95.3%, with a mean intensity of 15.0 (range 1-87). The infected salmon were kept in the laboratory where the growth of the cestodes was studied for eleven months. Mean length of the cestodes increased with time, but a large variation among the cestodes was observed. Growth and maturation of the cestodes were dependent on host size and the number of worms present in the intestine. No evidence of mortality of Eubothrium sp. was observed during the experimental period.
Dose confirmation studies of the cestocidal activity of pyrantel pamoate paste were conducted at two sites in North America during 2001. Horses with naturally-acquired cestode infections were identified by detection of typical Anoplocephala spp. eggs in feces collected between 7 and 92 days prior to treatment. Twenty and 22 horses were enrolled at Site 1 (Urbana, IL) and Site 2 (Knoxville, TN), respectively. Candidate horses were acclimated to study conditions for 14 days, ranked by length of interval since coprologic confirmation, and allocated randomly to one of two treatment groups: (T1) pyrantel pamoate paste 13.2mg pyrantel base per kilogram body weight administered orally, and (T2) untreated controls. Individual doses of pyrantel pamoate paste were prepared on the basis of contemporaneous body weights and administered to Group T1 horses on Day 0. Trained personnel monitored the animals at regular intervals after treatment to detect potential adverse reactions. Horses were euthanatized and necropsied 10-12 days after treatment. The contents of the large and small intestines were collected, and the walls of each organ were rinsed with water and inspected. Attached cestodes were recovered and preserved in 10% formalin. The intestinal contents and rinsed ingesta were washed over a #10-mesh (2mm aperture) sieve and tapeworms were extracted and preserved. Recovered cestodes were counted and examined at 1-4x magnification for identification to genus and species. At Site 1, specimens of Anoplocephala perfoliata were recovered from seven of 10 control horses, and from one of 10 horses treated with pyrantel pamoate. Mean cestode numbers were 4.52 in the control group and 0.07 for treated horses. At Site 2, cestodes were found in 10 of 11 controls (mean 26.2) and in five of 11 horses (mean 1.2) treated with pyrantel pamoate. In both studies, Group T1 means were significantly lower than the control group (P<0.005). The calculated efficacies were 98.4 and 95.5% at Sites 1 and 2, respectively. In two dose-confirmation studies, a single, oral treatment of pyrantel pamoate paste (19.13% w/w pyrantel base) at 13.2mg/kg was >or=95.5% effective against A. perfoliata in naturally-infected horses.
Sequence variation within 3 morphologically defined species of the anoplocephalid cestode genus Progamotaenia (P. ewersi, P. macropodis and P. zschokkei) was investigated using the cytochrome c oxidase subunit 1 gene. The magnitude of genetic variation detected within each morphospecies suggests that, in each instance, several cryptic species are present. Within P. ewersi, 5 genetically distict groups of cestodes were detected, 1 shared by Macropus robustus and M. parryi in Queensland, 1 in M. agilis from Queensland, 1 in Petrogale assimilis from Queensland, 1 in Macropus fuliginosus from South Australia and 1 in Wallabia bicolor from Victoria. In P. macropodis, cestodes from M. robustus from Queensland, Western Australia and the Northern Territory, M. parryi from Queensland and M. eugenii from South Australia were genetically distinct from those in Wallabia bicolor from Queensland and Victoria and from M. fuliginosus from South Australia. P. zschokkei consisted of a number of genetically distinct groups of cestodes, 1 in Lagorchestes conspicillatus and L. hirsutus from Queensland and the Northern Territory respectively, 1 in Petrogale herberti, P. assimilis and M. dorsalis from Queensland, 1 in Onychogalea fraenata from Queensland, 1 in M. agilis from Queensland and 1 in Thylogale stigmatica and T. thetis from Queensland. In general, genetic groups within each morphospecies were host specific and occurred predominantly in a particular macropodid host clade. Comparison of genetic relationships of cestodes with the phylogeny of their hosts revealed examples of colonization (P. zschokkei in M. agilis) and of host switching (P. zschokkei in M. dorsalis).
Twenty species of helminth parasites were identified from fox, wolf, jackal and wild cat material collected in Greece. Of the 314 foxes (Vulpes vulpes) examined, 18 helminth species were recovered comprising one trematode, eight cestodes, seven nematodes and two acanthocephalans, with the cestode species Mesocestoides sp. (73.2%), Joyeuxiella echinorhynchoides (24.5%) and the nematode species Uncinaria stenocephala (43.9%), and Toxara canis (28.6%) being the most prevalent. Five cestode and three nematode species were reported from six wolves (CaniS lupus), together with one trematode, three cestode and four nematode species from five jackals (Canis aureus) and two cestode and three nematode species from four wild cats (Felis silvestris) examined. The species J. echinorhynchoides, Taenia crassiceps and Onicola canis and the genera Spirometra, Rictularia and Pachysentis are reported here for the first time in Greece. The results are discussed in the light of the feeding characteristics of wild carnivores in rural areas of Greece.
Among flatworms with parasitic and commensal modes of existence, parthenogenesis and asexual multiplication appear to be largely confined to the Digenea and Cestoda, the only parasitic platyhelminths that routinely utilize indirect life-cycles. Parthenogenesis is apparently restricted to a minority of adult digeneans and cestodes inhabiting their final hosts, and a survey is made of the particular modes of parthenogenesis (i.e. apomictic, automictic and generative) which are employed by such adults. Asexual (amictic) multiplication, in the form of fissioning, is demonstrated by young adults of the cyclophyllidean cestode, Mesocestoides corti, but is otherwise not exhibited by adult cestodes or digeneans, other than in the perplexing phenomenon of proglottid formation in polyzoic tapeworms. Secondary multiplication is of ubiquitous occurrence in digenean life-cycles in the form of the proliferation which takes place within sporocysts and rediae (germinal sacs) located in the first intermediate host. The controversy concerning the nature of this multiplication is reconsidered in the context of recent findings which have centred on cellular aspects. On the basis of present evidence germinal sac multiplication should be regarded as an asexual rather than a parthenogenetic process. The cestode asexual multiplication which occurs in intermediate hosts is a function of the metacestode stage of development. Metacestode proliferation is only known from about 20 species and 6 families of polyzoic cestodes with approximately half the described instances occurring in the family Taeniidae. The organization of these proliferative metacestodes, findings concerning their totipotent stem cells and the ontogeny of buds and new scolices are all reviewed. Finally, the capacity for population expansion of multiplicative larval digeneans and metacestodes are compared, while the ecological roles and the genetical consequences of both parthenogenesis and amictic multiplication in the two taxa are also examined.
The article is based on the results of helminthological observations made on kittiwake Rissa tridactyla and glaucous gull Larus hyperboreus in 1991-2001 in different areas of the Barents Sea (Eastern Murman coast, Franz Josef Land, Novaya Zemlya, Spitzbergen). 18 helminth species (2 trematodes, 11 cestodes, 4 nematodes, and 2 acanthocephalans) were recorded in the kittiwakes and 19 (3 trematodes, 9 cestodes, 5 nematodes and 2 acanthocephalans) species were recorded in the glaucous gulls. Trematodes were absent in the birds collected at the Franz Josef Land and the northern island of Novaya Zemlya. 3 trematode species, namely Gymnophallus sp. (somateria?), Microphallus sp. 1 (M. pseudopygmaeus), and Cryptocotyle lingua were found in the glaucous gulls of western Spitzbergen. It was supposed that the life cycles of these parasites can be completed there. On the other hand, coastal ecosystems of Arctic archipelagoes turn out to be favourable for the transmission of some cestodes. This is closely connected with the regional traits in the marine bird diet, namely the increase of the amphipod (intermediate hosts of hymenolepidids and some dilepidids) and polar cod (supposed second intermediate host for some tetrabothriids) portion in Arctic. As a result, cestodes are the base of the helminth fauna of kittiwakes and glaucous gulls of the Barents Sea, by their species richness, prevalence and abundance. Nematodes and acanthocephalans were represented by a few species with low infection intensity. The main ecological factors affected the regional difference in the species richness and abundance of the helminths parasitising kittiwakes and glaucous gulls in the Barents Sea are proposed. Those are regional climatic features and regional traits in the behaviour and food priorities of birds, and also the distribution of the helminths intermediate hosts, invertebrates and fishes. The phenomenon of host specificity lowering with respect to the definitive host was recorded in some cestode species (Microsomacanthus diorchis, M. microsoma, and Arctotaenia tetrabothrioides) on the border of their distribution ranges, the coastal ecosystems of Arctic.
Previous electrophoretic studies (Renaud et al., 1983) carried out on the Cestode Bothriocephalus scorpii (Mueller, 1776) showed that the populations parasiting the Turbot and the Brill on the Mediterranean coast, are two distinct species: Bothriocephalus (supra sp. scorpii) gregarius and Bothricephalus (supra sp. scorpii) barbatus respectively. This work has been done with the purpose of identifying these two species by using biochemical tests. The study of whole body proteins by electrophoresis of zones of acrylamide gel shows the existence of nineteen distinct protein fractions in both populations. Among those different protein fractions, two of them (Rf 53 and Rf 87) are present only in the Cestode of the Brill and one (Rf 42) seems to be specific of the Turbot. On the other hand, the fraction of Rf 27 is present only in the Cestodes of the Brill. The immunoelectrophoretic study of antigenic components shows seven or eight major fractions depending on the source of protein, five of them being common to both. The reactions of absorption of antiserum permitted characterization of three arcs of precipitation proper in the Cestodes of the Brill corresponding to protein fractions of Rf (27, 53, 87) and three arcs in the Cestodes of the Turbot, corresponding to protein fractions of Rf (42, 21, 66).
Parasitic helminths have developed complex mechanisms to modulate host immunity. In the present study we found that previous infection of mice with the cestode Taenia crassiceps favours parasitemia and induces larger cutaneous lesions during both Leishmania major and Leishmania mexicana co-infections. Analysis of cytokine responses into draining lymph nodes indicated that co-infection of T. crassiceps-Leishmania did not inhibit IFN-gamma production in response to Leishmania antigens, but significantly increased IL-4 production. Additionally, anti-Leishmania-specific IgG1 antibodies and total IgE increased in co-infected mice, whereas, IgG2a titers remained similar. Macrophages from Taenia-infected mice displayed increased mRNA transcripts of arginase-1, Ym1, and Mannose Receptor, as well as greater production of urea (all markers for an alternate activation state) compared to macrophages from Leishmania-infected mice. In contrast, lower mRNA transcripts for IL-12p35, IL-12p40, IL-23p19, and iNOS were detected in macrophages obtained from cestode-infected mice compared to uninfected and Leishmania-infected mice after LPS stimulation. The presence of cestode also generated impaired macrophage anti-leishmanicidal activity in vitro, as evidenced by the inability of these macrophages to prevent Leishmania growth compared to macrophages from uninfected mice. This was observed despite the fact that both groups of cells were exposed to IFN-gamma. Flow cytometry showed high IFN-gammaR expression on Taenia-induced macrophages. Thus, lack of response to IFN-gamma is not associated with the absence of its receptor. Our data suggest that cestode infection may favour Leishmania installation by inducing alternatively activated macrophages rather than inhibiting Th1-type responses.
Five cestode, one monogenean, and two nematode species comprised the "normal" intestinal helminth fauna of Raja naevus in British waters. An additional two nematodes, a digenean, an acanthocephalan and a crustacean recorded are considered to be accidental infections. Geographical differences in the species composition and level of infection are noted and discussed. Short descriptions of the tetraphyllidean cestode Echeneibothrium sp. and the nematode Capillaria sp. are given, but the species, although probably both new, are left unnamed. The intensity of cestode infections show two patterns associated with host length and these are discussed in relation to variations in host diet. Speculations are made on the cestode life cycles. Only Echeneibothrium sp. numbers showed any significant variation associated with host sex.
The ultrastructure of the teguments of the cyclophyllidean cestodes Cotugnia polyacantha and Killigrewia streptopelia naturally infecting the dove Streptopelia senegalensis aegyptiaca, was studied using transmission electron microscopy. The two cestodes inhabit two distinct sites in the small intestine of the same bird. Observations revealed basic similarity between the two cestodes, though, marked differences between the tegument structure details of the two species regarding the structure and dimension of microtriches, types and distribution of vesicles among the regions of the tegumental/perikaryal complex, structure of subtegumental connective tissue and subtegumental muscle layer. The significance of these observations was discussed in possible relation to the different physico-chemical environments known to occur where each cestode resides.
We recovered the cestode Shipleya inermis from 79 of 82 short-billed dowitchers, Limnodromus griseus Gmelin, collected at various locations and times along their migratory route. Previous studies that examined various aspects of the cestode's biology were limited to North America. Data collected from North and South America in the present study provide new information on the geographical and seasonal distribution of this cestode. Although prevalence of infection was high at all times of the year, mean abundance varied from season to season and was significantly higher during the winter months than in the summer, suggesting that most recruitment takes place on the wintering grounds. Sexually mature and gravid cestodes were recovered at all locations, indicating S. inermis is a ubiquitous parasite within the host's range. Shipleya inermis showed a marked tendency to occur in pairs of male and female strobila. Analysis of the patterns of occurrence suggests that S. inermis is a protogynous hermaphrodite that usually becomes regionally dioecious, possibly in response to some form of interaction between individuals.
The time course of intestinal infection of golden hamsters (Mesocricetus auratus) with Taenia crassiceps was monitored every 2 days up to day 26 postinfection (p.i.). The isolate used was originally obtained from Clethrionomys rutilus on St. Lawrence Island, Bering Sea (USA), and shows a high level of enteral establishment without parenteral infection. Following oral administration of various numbers (3, 15, 30, or 60) of metacestodes, proportional numbers of cestodes attached their scolices to the mucosa of the middle (one-third) segment of the small intestine. Except for animals given 3 metacestodes, dislocation of cestodes to the posterior parts of the intestine was noted on days 10-14 p.i. and began faster in animals that had received larger numbers of metacestodes. Concurrent with dislocation or elimination of cestodes, there existed distinct increases in intestinal eosinophil peroxidase and myeloperoxidase activities. The number of mast cells in the lamina propria peaked on day 16 p.i., and specific serum IgG began to increase within 1 week p.i. The level of all these changes was dose-dependent. In prednisolone-treated animals that received 60 metacestodes, dislocation of cestodes was not evident, and mucosal inflammatory changes were suppressed to a considerable extent. The findings of this study are discussed as a model for the study of canine taeniasis.
Antigen B (AgB), an immunodominant component of the cestode parasite Echinococcus granulosus, presents homology to and shares apparent structural similarities with helix-rich hydrophobic ligand binding proteins (HLBPs) from other cestodes. In order to investigate the fatty acid binding properties of AgB, two of its subunit components (rAgB8/1 and rAgB8/2) were expressed in Escherichia coli and purified, and the native antigen was purified from the hydatid cyst fluid by affinity chromatography using a monoclonal antibody raised against rAgB8/1. The interaction of the purified native and recombinant proteins with the fluorescent ligands DAUDA, ANS, DACA and 16-AP was investigated. The palmitic acid derived fluorescent ligand, 16-AP, showed the greatest enhancement in fluorescence when bound to native AgB or to its recombinant subunits, and the dissociation constants for 16-AP binding were determined. Surprisingly, in contrast to HLBPs from other cestodes, interactions with other fatty acids, including palmitic acid, caused an increase in fluorescence instead of competing with 16-AP. Our results suggest that AgB might have evolved different functions in the binding of hydrophobic compounds, dependent on cestode environment.
Infection by the cestode Taenia taeniaeformis was investigated within numerous cyclic populations of the fossorial water vole Arvicola terrestris sampled during 4 years in Franche-Comté (France). The relative influence of different rodent demographic parameters on the presence of this cestode was assessed by considering (1) the demographic phase of the cycle; (2) density at the local geographical scale (<0.1 km2); (3) mean density at a larger scale (>10 km2). The local scale corresponded to the rodent population (intermediate host), while the large scale corresponded to the definitive host population (wild and feral cats). General linear models based on analyses of 1804 voles revealed the importance of local density but also of year, rodent age, season and interactions between year and season and between age and season. Prevalence was significantly higher in low vole densities than during local outbreaks. By contrast, the large geographical scale density and the demographic phase had less influence on infection by the cestode. The potential impacts of the cestode on the fitness of the host were assessed and infection had no effect on the host body mass, litter size or sexual activity of voles.