Hymenolepis diminuta utilizes the envelope surrounding Moniliformis moniliformis in order to survive in the cockroach host.

The acanthocephalan Moniliformis moniliformis is surrounded by a membranous envelope that protects the parasite from hemocytic attack in the cockroach host. If injected into a cockroach infected with M. moniliformis, hatched oncospheres of the tapeworm Hymenolepis diminuta are able to penetrate this envelope and, once inside, utilize its protective function in order to develop. These "double parasites" were infective to rats.

Axenic growth of oncospheres of Hymenolepis citelli (Cestoda) to fully developed cysticerocoids.

Cysticercoids of the cestode Hymenolepis citelli were grown axenically in vitro from the oncosphere to stages infective for the mammalian host. Reducing agents were an essential component of the culture medium. Of several reducing agents tested, L-cysteine was the most effective. Concentration of reducing agent was critical in that excessive amounts induced abnormal growth.

Tapeworm identification in the fat sand rat (Psammomys obesus obesus).

The identification of a tapeworm (Rodentolepis nana, formerly named Hymenolepis nana) infection in a research breeding colony of sand rats (Psammomys obesus obesus) was complicated because of the unexpected long length (< 150 mm) of the worms. Other morphologic features that were consistent with this identification included the number (24), size (16 mm), and shape of the hooks on the rostellum. No evidence of intermediate hosts was found in the colony. Previous surveys of natural populations of sand rats had not identified this tapeworm. However, a detailed search of the literature revealed that variation in the size of R. nana had been reported, thus supporting the final identification of the tapeworm. R. nana is important and interesting because of its zoonotic potential and because it is the only tapeworm that is able to infect its definitive host without use of an intermediate host. This report is presented to help clarify the ambiguity found in the laboratory animal literature about the differences in the size of R. nana among rodent species used in research.

[The effect of final host species on invasive activity of Sobolevicanthus gracilis (Cestoda, Hymenolepididae) oncospheres to intermediate hosts (Ostracoda)]. / Wplyw gatunku zywiciela ostatecznego na aktywnosc inwazyjna onkosfer Sobolevicanthus gracilis (Cestoda, Hymenolepididae) wzgledem zywicieli posrednich (Ostracoda).

Two species of ostracods: Heterocypris incongruens and Cypridopsis vidua were used as experimental intermediate hosts for Sobolevicanthus gracilis, with Anas platyrhynchos dom. and Gallus gallus as the two experimental final hosts. Three series of fourth-fold passages: in hens, from hens to ducks, and back into hens--via ostracods--were accomplished. The fourth series of passages--in turn to ducks--was carried out for confirmation the results obtained. The index of infective activity was calculated for each experimental series. It has been stated that the infective activity of oncospheres to H. incongruens differed from final host species to species, being clearly higher in larvae from hens then from ducks. No differences of the index depended on final host species were noticed in relation to C. vidua. The possible explanations of the results are discussed.

[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).

[The effect of temperature on the infective activiey oncospheres of Diorchis stefanskii hymenolepididae]. / Wplyw dzialania temperatury na aktywnosc inwazyjna onkosfer Diorchis stefanskii Czapl. (Hymenolepididae).

Heterocypris incongruens (RAMD.) was selected as an intermediate host, having emerged as the main host for Diorchis stefanskii Czapl. in experimental conditions. It was found that the index of infective activity for larvae of D. stefanskii was high on the first day, amounting to 50-54%, with an extensity of infection of 100%. The infective activity of larvae declined slowly but steadily at the low temperature (5 degrees C). Oncospheres retained their infective activity for more than 2.5 months. In contrast, in culture at 18-20 degrees C and 25 degrees C, the infective activity of larvae had declined rapidly only a few days into the experiment. The irrevocable loss of tapeworm infectivity occurred at temperatures of -5 degrees C and +38 degrees C, at which 100% of oncospheres died.

Infectivity of Hymenolepis nana eggs from faecal pellets in the rectum of mice.

The infectivity of Hymenolepis nana eggs from faecal pellets in the rectum of mice was compared with that of the eggs in gravid proglottids of adult H. nana and with that of the eggs in excreted faecal pellets to find out a simple method for collecting H. nana eggs of high infectivity to mice. Eggs from faecal pellets in the rectum showed higher infectivity than those from gravid proglottids and as high infectivity as those from gravid proglottids selected by a watch-glass rotation technique. Eggs in faecal pellets in the rectum did not lose infectivity until 4 h after they were excreted and exposed to the air at room temperature (27-28 degrees C) with relative humidity of 35-40%. However, the eggs lost infectivity significantly 17 h after excretion onwards.

The dynamics of infection of Tribolium confusum by Hymenolepis diminuta: the influence of infective-stage density and spatial distribution.

The mean parasite burden of a population of Tribolium confusum is shown to rise to a plateau as the exposure density of infective eggs of Hymenolepis diminuta increases. The level of this plateau is shown to be dependent on the nutritional status of the host population, being depressed from approximately 18 cysticeroids/beetle in hosts which have been starved prior to experimentation, to approximately 2 cysticercoids/beetle in satiated hosts. A simple model is used to describe the shape of this infection functional response in terms of the predator-prey interaction between hosts (T. confusum) and parasite infective stages (H. diminuta eggs). The distribution of successful infections/host is shown to be over-dispersed, even when hosts are exposed to infective stages arranged in a uniform spatial pattern. The over-dispersion of parasite numbers/host is shown to become more severe as the spatial pattern of infective stages changes from under-dispersed, through random, to over-dispersed. Experimental results are discussed in relation to the dynamics of parasite-host interactions, in which infection takes place by host ingestion of a free-living infective stage.

The rostellar tegumentary cytoplasm of the metacestode of Hymenolepis diminuta (Cyclophyllidea: Cestoda).

Prior to scolex-retraction, the tegumentary syncytial cytoplasm of the presumptive rostellar region of Hymenolepis diminuta (from Tenebrio molitor kept at 26 degrees C) is indistinguishable from that of the rest of the cysticercoid. At 1 day after scolex-retraction differentiation of the rostellum has commenced, the tegumentary cytoplasm containing a small number of membrane-bound, ovoid, electron-dense granules which are absent from all other tegumentary regions of the metacestode. By 3 days after scolex-withdrawal there is a substantial increase in the number of ovoid granules within the rostellar tegumentary syncytium and the Golgi systems of the rostellar cytons are highly secretory. At this stage, although the cyst wall tissues are not fully developed, the metacestode is infective. This early and rapid development of the rostellar region presumably enables the 'adult' condition to be readily attained. In older metacestodes there is a progressive accumulation of ovoid granules within the rostellar tegumentary cytoplasm, accompanied by a decrease within the rostellar cytons. At 23 days following scolex-retraction the rostellar syncytium has the appearance of that of the adult tapeworm. The rostellar cytons also produce tegumentary discs and vesicles and are therefore regarded as homologous to the other tegumentary cytons of the metacestode.

Survival of parasite eggs upon storage in sludge.

Destruction rates of parasite eggs in stored sludge were examined to help understand the fate of these agents of enteric diseases in sludge lagoons. Eggs from the roundworms, Ascaris spp., Toxocara spp., Trichuris spp., and the tapeworm, Hymenolepis spp., were treated with domestic sludges by aerobic or anaerobic processes. Sludge samples seeded with eggs were stored at 4 or 25 degrees C or in a container inserted into the ground to simulate lagoon conditions. The number of eggs recovered from the samples decreased with storage time. The viability and infectivity of eggs recovered were related to the storage temperature; i.e., the eggs stored at 4 degrees C remained viable longer than those stored at 25 degrees C. After 25 months at 4 degrees C, the Toxocara eggs and some Ascaris eggs remained both viable and infective, whereas most of these eggs stored at 25 degrees C were rendered nonviable after 10 to 16 months of storage in sludge. Although storage temperature was found to be the most important factor affecting the destruction and viability of these eggs, other factors, such as the type of sludge digestion, whether or not the eggs were digested along with the sludge or added later, storage in the soil versus sludge, pH, and egg species also exhibited some minor effects. These controlled laboratory studies suggest that lagooning of sludge can be an effective method for the elimination of parasite eggs, particularly in warmer geographical locations.

An ultrastructural analysis of cyst wall development in the metacestode of Hymenolepis diminuta (Cestoda).

A series of development stages (I-XI) have been devised to describe the development of the cyst wall of the metacestode of Hymenolepis diminuta. The cyst wall possesses tegumentary, muscular, fibrous and inner cyst tissues, the developmental rates and differentiation patterns of which are not identical. The tegumentary tissue differentiates posteriorly. Its microvillus-bearing distal cytoplasm remains simple until scolex retraction, after which rapid increase in depth followed by vacuolation occurs and basal membrane infoldings surround Phase 3 fibrogenesis fibrils. Senescence, which also affects the tegumentary cytons, then ensues. The muscle system development is posteriad and maturation, completed before scolex retraction, is followed by myocyton senescence. Posteriorly differentiated fibroblasts commence Phase 1 fibrogenesis after scolex retraction and the primary fibrous zone is fully established within approximately 6 days. Phase 2 and 3 fibrogenesis develop centrifugally, the fibrils of Phase 2 surrounding the tegumentary cytons and myocytons prior to their senescence, and those of Phase 3 lying more peripherally. The inner cyst tissue, established posteriorly, differentiates anteriorly, centripetally and early, the penultimate stage commencing just before scolex retraction, about 6 days after which the final maturation junctional complexes start development. Neither in vitro excystment nor infectivity of the definitive host can be satisfactorily achieved before the initial development of the primary fibrous zone. This may play a skeletal role during excystment, and is shown to be unaffected by the digestive enzymes which cause loss of cytoplasmic integrity in the outer regions of the cyst.

Failure to infect laboratory rodent hosts with human isolates of Rodentolepis (= Hymenolepis) nana.

Confusion exists over the species status and host-specificity of the tapeworm Rodentolepis (= Hymenolepis) nana. It has been described as one species, R. nana, found in both humans and rodents. Others have identified a subspecies; R. nana var. fraterna, describing it as morphologically identical to the human form but only found in rodents. The species present in Australian communities has never been identified with certainty. Fifty one human isolates of Rodentolepis (= Hymenolepis) nana were orally inoculated into Swiss Q, BALB/c, A/J, CBA/ CAH and nude (hypothymic) BALB/c mice, Fischer 344 and Wistar rats and specific pathogen free (SPF) hamsters. Twenty four human isolates of R. nana were cross-tested in flour beetles, Tribolium confusum. No adult worms were obtained from mice, rats or hamsters, even when immunosuppressed with cortisone acetate. Only one of the 24 samples developed to the cysticercoid stage in T. confusum; however, when inoculated into laboratory mice the cysticercoids failed to develop into adult worms. The large sample size used in this study, and the range of techniques employed for extraction and preparation of eggs provide a comprehensive test of the hypothesis that the human strain of R. nana is essentially non-infective to rodents.

Reactive oxygen intermediates from eosinophils in mice infected with Hymenolepis nana.

A large number of eosinophils were recruited to the intestinal villi after infection with Hymenolepis nana. Eosinophil numbers were increased more rapidly in challenged mice than in primary infected mice. Local intestinal eosinophils from challenged mice showed more extracellular oxygen radical release, as assessed by histochemical methods using nitro blue tetrazolium, accompanied with tissue injury and larval degradation. Intestinal eosinophils isolated from the lamina propria induced specific oxygen radical generation in response to H. nana oncosphere extract as measured by luminol-dependent chemiluminescence. This response was stronger in challenged mice than in primary infected mice. Radical generation from uninfected mice was negligible. Lipid peroxidation in the small intestine, as measured by formation of malondialdehyde, was increased during H. nana challenge infection, the peak activity coinciding with the elimination of challenge larvae. Continuous administration of a NADPH oxidase inhibitor to sensitized mice interfered with the degeneration of challenge larvae. These results suggest that intestinal eosinophils may be the major contributor to oxygen radical production in response to H. nana and that reactive oxygen species may play a part of effector molecule in the resistance to reinfection with H. nana.

Enteroparasitos en niños residentes en zona rural del Partido del Carmen de Patagones: Provincia de Buenos Aires, Argentina / Enteroparasites in children living in rural areas at the Partido de Carmen de Patagones: province of Buenos Aires, Argentina

Como parte del programa de atención primaria de la salud (APS) del año 1996, y en virtud que no existían datos epidemiológicos referidos a enteroparásitos hallados en niños de 0 a 14 años, residentes en una zona rural del Partido de Carmen de Patagones, Provincia de Buenos Aires, es que se realizó el presente estudio epidemiológico descriptivo. Se estudiaron 210 niños a los que se les efectúo un estudio parasitoscópico seriado de materia fecal y mucus anal. Los resultados mostraron que el 60,5 por ciento de la población estudiada era portadora de algún parásito intestinal. El monoparasitismo hallado fue de 67 por ciento, mientras que 33 por ciento restante presentó entre 2 y 5 formas parasitarias. El espectro parasitario fue el siguiente: entamoeba coli 31,5 por ciento, giardia lamblia 24,7 por ciento; enterobius vermicularis 18 por ciento; hymenolepis nana 10,4 por ciento; blastocystis hominis 10,4 por ciento; 10,3 por ciento; chilomastix mesnili 2,5 por ciento; entamoeba hystolytica 0,9 por ciento y trichuris 0,5 por ciento. La distribución parasitaria en los distintos sectores estudiados fue en general homogénea excepto para H. nana la cual presentó una prevalencia más altas en zonas de riesgos con relación a la zona seca. Los resultados obtenidos fueron comunicados a las autoridades sanitarias correspondientes