The role of chewing lice (Phthiraptera: Philopteridae) as intermediate hosts in the transmission of Hymenolepis microps (Cestoda: Cyclophyllidea) from the willow ptarmigan Lagopus lagopus (Aves: Tetraonidae).

The cestode Hymenolepis microps is an intestinal parasite of tetraonid birds, including the willow ptarmigan (Lagopus lagopus). This parasite is able to maintain a high prevalence and intensity throughout the year, even in a subarctic environment in bird populations with relatively low host densities, indicating effective transmission routes. Willow ptarmigan consume mainly vegetal material and active consumption of invertebrates is confined to the first two or three weeks of life. Ptarmigan are infected by different species of ectoparasites, of which two species of feather lice, Lagopoecus affinis and Goniodes lagopi, are the most abundant. In this study, we explored the hypothesis that feather lice may be suitable intermediate hosts for H. microps. We applied histological techniques and light microscopy to investigate lice for the presence of larval cestode stages (cysticercoids). We found 12 cysticercoid-like structures inside chewing lice collected on L. lagopus hosts harbouring H. microps. In addition, a polymerase chain reaction (PCR) screening of Ischnocera lice DNA, targeting the 18S rRNA gene of the cestode, showed positive results for two different short fragments of the 18S rRNA gene of H. microps which were sequenced from lice collected on birds. Both independent lines of evidence support the hypothesis that Ischnocera lice might be suitable intermediate hosts in the life cycle of H. microps in L. lagopus.

The anthelmintic efficacy of natural plant cysteine proteinases against Hymenolepis microstoma in vivo.

Little is known about the efficacy of cysteine proteinases (CP) as anthelmintics for cestode infections in vivo. Hymenolepis microstoma is a natural parasite of house mice, and provides a convenient model system for the assessment of novel drugs for anthelmintic activity against cestodes. The experiments described in this paper indicate that treatment of H. microstoma infections in mice with the supernatant of papaya latex (PLS), containing active cysteine proteinases, is only minimally efficacious. The statistically significant effects seen on worm burden and biomass showed little evidence of dose dependency, were temporary and the role of cysteine proteinases as the active principles in PLS was not confirmed by specific inhibition with E-64. Worm fecundity was not affected by treatment at the doses used. We conclude also that this in vivo host-parasite system is not sensitive enough to be used reliably for the detection of cestocidal activity of compounds being screened as potential, novel anthelmintics.

Basic and applied problems in developmental biology and immunobiology of cestode infections: Hymenolepis, Taenia and Echinococcus.

Differentiation and development of parasites, including longevity in host animals, are thought to be governed by host-parasite interactions. In this review, several topics on the developmental biology of cestode infections are discussed from immunobiological perspective with a focus on Hymenolepis, Taenia and Echinococcus infections. The basic premise of this review is that 'differentiation and development of cestodes' are somehow affected by host immune responses with an evolutionary history.

[Activity of the anthelmintic agent trichlorophen on the models of human helminthiasis]. / Aktivnost' otechestvennogo antigel'mintika trikhlofena na modeliakh gel'mintozov cheloveka.

Trials of trichlorophen have shown its high efficacy on models of cestode infections: hymenolepiasis (at the adult and cysticercoid stages of development on three types of animals: outbred albino mice, albino rats and golden hamsters), preimaginal echinococciasis alveolaris, larval alveolar echinococciasis (at the early stage of development of the parasite in experiments on cotton rats). The high nematodical activity of trichlorophen was first found on models of trichocephaliasis in DBA/2y mice, nippostrongyloidiasis (in in vitro experiments), and aspiculuriasis in outbred mice. The agent proved to be ineffective at the tissue developmental stage of Hymenolepsis nana (H. nana), the dwarf tapeworm, in albino mice, during experimental opisthorchiasis in golden hamsters. It showed a low efficacy in treating trichinosis in outbred albino mice. Unlike carbamatebenzimidazoles, trichlorophen was inactive at the tissue stage of H. nana; it exerted no effects on the eggs of a dwarf tapeworm in trichinosis. Trichlorophen was also inactive in treating experimental opisthorchiasis in golden hamsters.

Hymenolepis microstoma: direct life cycle in immunodeficient mice.

The mouse bile duct tapeworm Hymenolepis microstoma requires beetles as the obligatory intermediate host. However, when congenitally athymic NMRI-nu mice were infected with the mature tapeworm and allowed to eat their own faeces with tapeworm eggs, the oncospheres penetrated the intestinal tissue and developed to cysticercoids. After excysting, growth to adult worms occurs in the lumen of the small intestine and bile duct. Furthermore, the same happened when NMRI-nu mice, non-obese diabetic severe combined immunodeficiency (NOD/Shi-scid) mice and NOD/Shi-scid, IL-2 Rgamma(null) (NOG) mice were orally inoculated with shell-free eggs of this parasite. Differences between the cysticercoids of H. microstoma and H. nana developed in the mouse intestinal tissues were: (i) the time course for the development of fully matured cysticercoids of H. microstoma in mice was about 11 days but only 4 days for H. nana; and (ii) cysticercoids of H. microstoma developed in mice had a tail while those of H. nana had none.

The embryonic development of the bodywall and nervous system of the cestode flatworm Hymenolepis diminuta.

Cestodes (tapeworms) are a derived, parasitic clade of the phylum Platyhelminthes (flatworms). The cestode body wall represents an adaptation to its endoparasitic lifestyle. The epidermis forms a non-ciliated syncytium, and both muscular and nervous system are reduced. Morphological differences between cestodes and free-living flatworms become apparent already during early embryogenesis. Cestodes have a complex life cycle that begins with an infectious larva, called the oncosphere. In regard to cell number, cestode oncospheres are among the simplest multicellular organisms, containing in the order of 50-100 cells. As part of our continuing effort to analyze embryonic development in flatworms, we describe here the staining pattern obtained with acTub in embryos and larvae of the cestode Hymenolepis diminuta and, briefly, the monogenean Neoheterocotyle rhinobatidis. In addition, we labeled the embryonic musculature of Hymenolepis with phalloidin. In Hymenolepis embryos, two different cell types that we interpret as neurons and epidermal gland cells express acTub. There exist only two neurons that develop close to the midline at the anterior pole of the embryo. The axons of these two neurons project posteriorly into the center of the oncosphere, where they innervate the complex of muscles that is attached to the hooklets. In addition to neurons, acTub labels a small and invariant set of epidermal gland cells that develop at superficial positions, anteriorly adjacent to the neurons, in the dorsal midline, and around the posteriorly located hooklets. During late stages of embryogenesis they spread and form a complete covering of the embryo. We discuss these data in the broader context of platyhelminth embryology.

Tapeworm infection reduces epithelial ion transport abnormalities in murine dextran sulfate sodium-induced colitis.

The rat tapeworm Hymenolepis diminuta was used to test the hypothesis that helminth infection could modulate murine colitis. Mice were infected with five H. diminuta cysticercoids, and colitis was evoked via free access to 4% (wt/vol) dextran sulfate sodium (DSS)-containing drinking water for 5 days. BALB/c mice were either infected with H. diminuta and 7 days later exposed to DSS (prophylactic strategy) or started on DSS and infected with H. diminuta 48 h later (treatment strategy). Naive and H. diminuta-only-infected mice served as controls. On autopsy, colonic segments were processed for histological examination and myeloperoxidase (MPO) measurement or mounted in Ussing chambers for assessment of epithelial ion transport. Cytokines (gamma interferon [IFN-gamma], interleukin 12 [IL-12], and IL-10) were measured in serum and colonic tissue homogenates. DSS treatment resulted in reduced ion responses (indicated by short-circuit current [Isc]) to electrical nerve stimulation, the cholinergic agonist carbachol, and the adenylate cyclase activator forskolin compared to controls. H. diminuta infection, either prophylactic or therapeutic, caused a significant (P < 0.05) amelioration of these DSS-induced irregularities in stimulated ion transport. In contrast, the histopathology (i.e., mixed immune cell infiltrate, edema, and ulcerative damage) and elevated MPO levels that accompany DSS colitis were unaffected by concomitant H. diminuta infection. Similarly, there were no significant differences in levels of IFN-gamma, IL-12, or IL-10 in serum or tissue from any of the treatment groups at the time of autopsy. We suggest that abolishment of colitis-induced epithelial ion transport abnormalities by H. diminuta infection provides proof-of-principle data and speculate that helminth therapy may provide relief of disease symptoms in colitis.

Interactions between rat C-reactive protein and adult Hymenolepis diminuta.

Interactions between adult Hymenolepis diminuta and rat C-reactive protein (CRP) were investigated in vivo and in vitro. Using an ELISA technique, serum levels of CRP were monitored in rats infected with 100 cysticercoids. Although infection increased the level of this protein in the early stages of parasitization, the increase was not significant until 35 days post-infection (p.i.). Secondary infections did not enhance the response. When H. diminuta was cultured in the presence of CRP, reduced worm motility and opaque areas were observed and electron microscopical studies revealed shedding of microtriches and lysis of the tegument. Initially, damage was restricted to the strobila which correlated with the regional distribution of phosphorylcholine as visualized using immunofluorescence.

Impairment of the chemical defence of the beetle, Tenebrio molitor, by metacestodes (cysticeroids) of the tapeworm, Hymenolepis diminuta.

The defensive glands of beetles, Tenebrio molitor, infected with metacestodes (cysticercoids) of Hymenolepis diminuta are everted less frequently upon stimulation, and contain less toluquinone (methylbenzoquinone) and m-cresol, than glands of uninfected controls. These differences, as shown in predation trials with wild rats, increase the likelihood that both cysticercoids and beetles will be ingested by the tapeworm's definitive host. This is the first documented case of a parasite inhibiting the chemical defence of an intermediate host, and one of only a few reports of parasite-induced manipulation of host biology supported by empirical evidence implicating facilitated parasite transmission between host species.

[The effect of crowding tapeworms Hymenolepis diminuta based on proglottids in the period of intensified variability]. / Wplyw stloczenia tasiemców Hymenolepis diminuta na budowe proglotydow w okresie ich wzmozonej zmiennosci.

Tapeworms obtained 13 months after the administration to rats of cysticercoids Hymenolepis diminuta - WMS il1 measured in 3-6-specimen populations an average of 677.9 mm in length while in 23-26-specimen populations an average of 356.9 mm in length. Strobilas of an exclusively unilateral (right-sided) position of genital pores (PGP) appeared in 76.3%-79.8% of tapeworms of the investigated groups. In such tapeworms belonging to 23-26-specimen populations the frequency of occurrence of typical proglottids containing 1 testis on the poral side and 2 testes on the aporal side (1p2a) and type 0p3a proglottids averaging 86.5% and 6.8%, respectively, declines in comparison to the average frequency of occurrence of proglottids of this type in 3-6-specimen populations amounting to 87.8% and 8.8%, respectively. The frequency of occurrence of four-testes (1p3a) proglottids averaged 5.5% in tapeworms from the 23-26-specimen populations and was 4.0% higher than the 1.5% average in tapeworms from the 3-6-specimen populations, in spite of the fact that in a population with a higher number of specimens proglottids are smaller and, therefore, have less room for an additional number of these organs. In tapeworms with variable PGP type 2p1a proglottids constituted the most frequent deviation in each of investigated group of different infection intensity. Their average frequency of occurrence rose from 0.4%-0.5% in tapeworms with unilateral PGP to an average of 5.5%-5.9% in tapeworms with variable PGP. Close positive correlation was found in tapeworms with variable PGP between the frequency of occurrence of such changes and the frequency occurrence of type 2p1a proglottids in every of investigated group (P < 0.01, r = from +0.887, to +0.918).

Postmortem migration of Hymenolepis diminuta (Cestoidea: Cyclophyllidea) in the laboratory rat.

Postmortem migration is of considerable concern in surveys and studies of parasite ecology where accurate estimates of parasite location is crucial. Yet, there is no quantitative information documenting this phenomenon. Twenty-seven Sprague-Dawley rats were each inoculated with 5 cysticercoids of Hymenolepis diminuta. Four weeks postinfection, 15 rats were killed by cervical dislocation. The small intestines of 3 rats were removed immediately and fast frozen. Additional groups of 3 rats each (experimentals) were processed at intervals of 30, 60, 120, and 240 min after death (AD). Four additional groups of 3 rats (controls) were killed and processed at 30, 60, 120, and 240 min in order to assess changes due to circadian movement. Changes in the position of the scolex and biomass (dry weight) were assessed as a proportion of small intestine length for the following criteria: anterior, median, and posterior location. The only significant within-group difference was an anterior shift in median biomass in the experimental group. Between-group differences were not evident at 30 min. Significant posterior shifts were found in anterior and median scolex position of the experimentals at 120 and 240 min AD, respectively. Median and posterior biomass shifted significantly anteriorly at 60 and 120 min AD in the experimental group, respectively, and worm range was significantly reduced in the experimentals at 120 min AD. There appears to be a 30-min period following host death in which H. diminuta does not change its position within the rat small intestine.

Estudio clínico epidemiológico y determinación de la eosinofilia en escolares con hymenolepiasis: Chuquibamba 1995

Se estudió 158 escolares de ambos sexos con edades entre los 5 y 16 años de edad del C.E. primario 41-045 del distrito de Chuquibamba, de ellos 24 fueron portadores de Hymenolepis nana(15.2 por ciento). La prevalencia por edades fue de 7 a 8 años: 18 por ciento; de 9 a 10 años: 25.5 por ciento; de 11 a 12 años: 7.4 por ciento; de 13 a 14 años: 12.5 por ciento. Prevalencia por sexo fue en varones: 12.6 por ciento; y en mujeres de 18.3 por ciento. De los 24 casos con H. nana, 23 de ellos fueron asociados con E. coli(25 por ciento) y con G. lamblia(17 por ciento). Los escolares infectados con H. nana, presentaron una sintomatología con predominio de la esfera digestiva: dolor abdominal(37.3 por ciento), diarrea(25.5 por ciento), náuseas(50 por ciento) y sensación de llenura(14.3 por ciento). Los factores epidemiológicos condicionantes a la infección por H. nana tiene valor estadístico: Saneamiento básico defectuosos con mala disposición de excretas y basuras 23.7 por ciento y 26.1 por ciento respectivamente; así mismo, el consumo de verduras crudas(25.5 por ciento), el no lavado de manos antes de comer(34.1 por ciento) son factores que influyen a la presencia de hymenolepiasis. La eosinofilia relativa(6 a 10 por ciento) así como la absoluta(501-1000 eos/mm3), fue de intensidad leve, 41.7 por ciento y 50 por ciento respectivamente; siendo el porcentaje promedio de eosinófilos 10.83 por ciento y de 907 eos/mm3

Reconsideration of the effects of selfing on the viability of Hymenolepis nana.

A single cysticercoid of Hymenolepis nana was orally administered to an SPF-ICR strain mouse which was congenitally free of H. nana. Gravid proglottids of the resulting adult worm (parental generation) were fed to flour beetles, Tribolium confusum. Six or 14 days later, one cysticercoid from the beetles was fed to each mouse. Gravid proglottids were subsequently recovered and fed to beetles as above. This procedure was repeated for more than 20 generations. H. nana can survive repeated selfing and has been maintained for at least 27 generations. No decrease in the proportion of cysticercoids into adults with repeated selfing was observed in our experiments. Our results appear to conflict somewhat with results reported previously. This discrepancy may be due to a difference in mice used as experimental hosts, although some other causal factors, e.g. fluctuation of infective rate or difference in the varieties of H. nana strain used cannot be excluded.

Resistance of mice to infection with the human strain of Hymenolepis nana.

Six attempts were made to infect mice by feeding them eggs of the human strain of Hymenolepis nana, but none was successful. No eggs were found in the mouse faeces 14 days after feeding, and no adult worms were recovered at post mortem examination. In attempts to induce cysticercoids to infect mice, beetles were either fed on infected human faeces or given Hymenolepis eggs on filter paper. Both methods were unsuccessful, as no cysticercoids were recovered six days after exposure of the beetles.

Differences in biological characteristics of two strains of the cestode Hymenolepis diminuta.

Biological characteristics of infectivity, growth rate and fecundity of Hymenolepis diminuta isolated from wild Rattus rattus in Japan were compared with parasites of Texas origin maintained for several generations in this and many other laboratories in laboratory bred Rattus norvegicus. The timing of development and maturation was similar in parasites from both sources, but the mean parasite dry weight was less and the mean egg production lower in Japanese parasites in both single and multiple infections. The differences persisted over 10 weeks in single infections, and were unaffected by rat strain. In all experiments there was much greater variation and heterogeneity in the biological characteristics of the Japanese parasites. It was concluded that the Texas parasites were better adapted to R. norvegicus and in the course of adaptation had become more homogeneous, and that the difference between the parasite strains had a complex genetic basis. Some Japanese parasites of the early isolated generations failed to produce normal eggs, but the proportion of these decreased in later generations. However, selected individual Japanese parasites whose egg production was equal to that of parasites of Texas origin did not produce offspring of larger mean size or higher mean fecundity, and heterogeneity of these characteristics was maintained. In the intermediate host, the mean number of cysticercoids of the Japanese isolate per beetle was higher than that of the Texas strain in Tribolium confusum but lower in Tenebrio molitor. The greater heterogeneity exhibited by Japanese parasites and the genetic basis of the strain difference are discussed with particular reference to geographical isolation, differences in definitive hosts and co-evolution of wild and laboratory host and parasite populations.

Cortisone-sensitive, innate resistance to Hymenolepis nana infection in congenitally athymic nude rats.

The innate resistance of the unnatural rat host to the mouse tapeworm Hymenolepis nana is cortisone sensitive but thymus independent. When congenitally athymic nude rats were orally given eggs, cysticercoids, or adult worms of H. nana, no lumenal adults were established except when they were treated with cortisone acetate during the expected lumenal development. The effect of cortisone to promote adult maturation in the rats was compared in nude and normal rats given eggs of H. nana. The fecundity of the worms (assessed by the fresh worm biomass and the number of infective eggs produced) was much higher in cortisone-treated nude rats than in cortisone-treated normal rats. When the nude rats reconstituted with thymocytes were given eggs and treated with cortisone, the fecundity of H. nana dropped to the same level as in cortisone-treated normal rats. It is strongly suggested that the unnatural rat host has thymus-independent cortisone sensitive resistance to an initial infection (which is the main component of the innate resistance and blocks the lumenal establishment of this parasite) and thymus-dependent resistance (which suppresses the established worms' fecundity and may be ascribed to acquired resistance to the ongoing infection).

Hymenolepis citelli and H. diminuta: worm burdens in homologous and heterologous infections in rats.

Primary and secondary infections of Hymenolepis citelli were followed in CFHB rats. In primary infections of 6, 20, and 50 cysticercoids, over 75% of the worms administered became established and grew. Thereafter, survival depended on the intensity of the primary infection. Acquired resistance to homologous challenge infections could be stimulated in rats by prior infection with H. citelli. The growth of secondary worms decreased as the intensity of the sensitizing infection increased. The protective response waned with time in the absence of the primary worms. Cross-protective responses between H. citelli and H. diminuta occur in rats infected previously with either parasite. Retardation in the growth of secondary worms may have an immunological basis.

Variation in the sizes of eggs and oncospheres and the numbers and distributions of testes in the tapeworm, Hymenolepis diminuta.

Four "strains" of Hymenolepis diminuta were examined for morphological variation. These included the ARME "strain" (currently maintained at the University of Keele, U.K.), the OSU "strain" (currently maintained at The Ohio State University) and the TOR (or UT) "strain" (currently maintained at the University of Toronto), all of which were derived from the parental RICE "strain," and the ANU "strain" (currently maintained at the Australian National University). Additionally, 2 separate "clonal" populations (populations derived from single cysticercoids) from both the OSU and ANU "strains" were examined. All "strains" and "clones" were maintained under identical conditions using Tenebrio molitor and male Sprague-Dawley rats as the intermediate and definitive hosts, respectively. The lengths and widths of eggs and larvae (oncospheres) passed in the hosts' feces, and the numbers and distributions of testes in proglottids were quantified and the data analyzed. Although analyses of the lengths and widths of eggs and larvae demonstrated significant differences among some "strains" and "clones," a discriminate analysis of the data indicated these parameters to be of questionable taxonomic significance. The eggs of all "strains" and "clones" consisted of 2 distinct populations differing in density and size but not infectivity; the relative proportions of eggs in the 2 populations were not determined. Considering all possible numbers and distributions of testes, 17 variations were seen in the strobilae of tapeworms. Analyses of the data demonstrated that the "strains" and "clones" could be differentiated clearly using only the frequencies of the 1p2a (1 poral and 2 aporal testes) or 1p3a distribution, or the frequencies of proglottids containing 3 or 4 testes; all other variations failed to clearly differentiate or group the various "strains" and "clones."(ABSTRACT TRUNCATED AT 250 WORDS)

Interactions of the cysticercoids of Hymenolepis diminuta and raillietina cesticillus in their intermediate host, Tribolium confusum.

This study was based on the experimental exposure of beetles to homologous and heterologous infections of Hymenolepis diminuta and Raillietina cesticillus. The results demonstrated that, for both species over the range of parasite densities employed, the presence of a primary infection had no effect on the establishment success of an homologous challenge infection. The establishment success of R. cesticillus cysticercoids was not affected by the presence of an H. diminuta infection. The existence of an R. cesticillus infection, however, severely reduced the establishment success of an H. diminuta infection. The reduction in H. diminuta establishment was greatest in R. cesticillus infections less than 10 days old. The plausibility of some of the mechanisms that are potentially responsible for the reduction in H. diminuta establishment success is discussed, as is the possible ecological significance of these results.