Zoonotic hydatidosis in donkeys: post mortum examination in the Zoo, Giza, Egypt

A total of 17 out of 160 donkeys slaughtered had hepatic hydatidosis as proved macroscopically and microscopically. The epidemiology of zoonotic echinococcosis/hydatidosis was reviewed and discussed.

Spermatozoon ultrastructure of the pseudophyllidean cestode Paraechinophallus japonicus, a parasite of deep-sea fish Psenopsis anomala (Perciformes, Centrolophidae)

This paper provides the first ultrastructural data on the spermatozoon of a pseudophyllidean cestode belonging to the family Echinophallidae, Paraechinophallus japonicus, parasitizing deep-sea fish Psenopsis anomala from Japan. The mature spermatozoon contains two axonemes of the 9+"1" trepaxonematan pattern, nucleus, cortical microtubules, and electron-dense granules. Its anterior extremity exhibits a single electron-dense crested body. One of the most interesting features of the mature spermatozoon is the presence of a ring of tubular structures encircling the axoneme. This character, previously reported in species of the families Bothriocephalidae and Triaenophoridae, may be unique to pseudophyllideans of the group "Bothriocephalidea", thus supporting the assumption that the order Pseudophyllidea is formed in fact by two unrelated clades; "Bothriocephalidea" and "Diphyllobothriidea". The posterior extremity contains the posterior part of the nucleus and the disorganized axoneme--a character previously not described in the Eucestoda.

In vitro effects of nitazoxanide on Echinococcus granulosus protoscoleces and metacestodes

OBJECTIVES

Infection of humans and domestic ruminants with the larval stage (metacestode) of Echinococcus granulosus results in cystic echinococcosis (CE). The metacestode causes a space-occupying lesion in visceral organs, most commonly in the liver. Benzimidazole carbamate derivatives, such as mebendazole and albendazole, are currently used for chemotherapeutic treatment of CE. In human patients, benzimidazoles have to be applied in high doses for extended periods of time, and adverse side effects are frequently observed. In order to evaluate alternative treatment options, the in vitro efficacy of nitazoxanide, a broad-spectrum drug used against intestinal parasites and bacteria, was investigated.

METHODS

Freshly isolated E. granulosus protoscoleces were subjected to nitazoxanide treatment (1, 5 and 10 microg/mL), and the effects on parasite viability were monitored by Trypan Blue staining and scanning electron microscopy. Protoscolex cultures were maintained further, until metacestode development took place. Metacestodes were then subjected to nitazoxanide treatment (10 microg/mL), and corresponding effects were visualized by scanning and transmission electron microscopy.

RESULTS

Dose-dependent protoscolex death within a few days of nitazoxanide treatment was observed. Subsequent in vitro culture of drug-treated protoscoleces confirmed the non-viability of parasites, while further cultivation of non-treated protoscoleces for a period of at least 3 months resulted in stage conversion and the formation of small metacestodes 3-4 mm in diameter. Nitazoxanide had a deleterious effect on these metacestodes, which was comparable to that of albendazole.

CONCLUSIONS

Our study indicates a potential for nitazoxanide as an alternative treatment option against CE.

Echinococcus granulosus protoscolex formation in natural infections

Echinococcus granulosus is a parasitic platyhelminth that is responsible for cystic hydatid disease. From the inner, germinal layer of hydatid cysts protoscoleces are generated, which are are the infective forms to the dog. Systematic studies on the cell biology of E. granulosus protoscolex formation in natural infections are scarce and incomplete. In the present report we describe seven steps in the development of protoscoleces. Cellular buds formed by a clustering of cells emerge from the germinal layer of hydatid cysts. The buds elongate and the cells at their bases seem to diminish in number. Very early on a furrow appears in the elongated buds, delimiting anterior (scolex) and caudal (body) regions. Hooks are the first fully-differentiated structures formed at the apical region of the nascent scolex. In a more advanced stage, the scolex shows circular projections and depressions that develop into suckers. A cone can later be seen at the center of the hooks, the body is expanded and a structured neck is evident between the scolex and the body. During protoscolex development this parasitic form remains attached to the germinative layer through a stalk. When fully differentiated, the stalk is cut off and the infective protoscolex is now free in the hydatid fluid.

In vitro culture of Echinococcus multilocularis and Echinococcus vogeli metacestodes: studies on the host-parasite interface

The larval stage of Echinococcus multilocularis causes alveolar echinococcosis (AE) in various mammalians including humans, while Echinococcus vogeli larvae cause a related disease which is also occasionally found in man. Traditionally, Echinococcus metacestodes have been maintained in the laboratory by serial transplantation passages into susceptible animals such as mice or gerbils, enabling the parasite to proliferate asexually. These experimental animal models have been used extensively to investigate host-parasite interactions and to study immunological events occurring at the host-parasite interface. However, with the use of laboratory animals it has always been difficult to investigate in more detail those factors modulating metacestode differentiation, and investigations on gene expression and respective regulation have been hampered by the complexity of the host-parasite interplay. There has been a need for an in vitro culture model which would enable researchers to dissect specific parasite compartments involved in the host-parasite relationship in more detail. This review summarises the studies leading to the development and application of a suitable in vitro culture model for the maintenance and proliferation of E. multilocularis and E. vogeli metacestodes, including the formation of protoscoleces, in a chemically defined medium devoid of host influence. These culture models have been used to study the basic parameters of metacestode in vitro proliferation and differentiation, and for the dissection of the ultrastructure and composition of the acellular laminated layer, the structure of which is predominantly involved in the physical interaction between the parasite and host immune and non-immune cells and tissues. For E. multilocularis, in vitro cultured parasites have been more extensively employed to study the localisation of several antigens, and to generate defined antigens for immunological studies. Although in vitro culture will not completely eliminate the need of animal experimentation, a wider application of this technique could significantly reduce the use of animals, and thus the costs and time required for respective experimental investigations.

Morphological variability and degenerative evolution of human hepatic hydatid cysts

The findings are presented of a macro and microscopic investigation of 89 hydatid hepatic cysts removed intact from 59 patients by total pericystectomy. Detailed analysis revealed significant morphostructural variability and cysts grouped into 10 types were characterized, providing useful clinical indications. Only 30 cysts resulted fertile (33.7%), probably due to mean age of sample; 7 of these were "classic" cysts, 1 "septated" and 22 "multivesicular" packed with daughter cysts (DC), of varying turgidity or collapsed. Among the remaining 59 sterile cysts, 52 were degenerated and classified as "hyperlaminated" cysts due to the presence of large convoluted sheets of laminar tissue (SLT) surrounded by varying amounts of caseous (40 specimens), granular (6) or gelatinous (6) matrix. Moreover, "multivesicular", "acephalocyst", "caseous" and "serous" cysts were also recovered among the sterile specimens. Some "multivesicular" cysts (14) appeared as "transitional forms" towards the various types of "hyperlaminated" cysts containing all different forms of DC and large SLT intermingled with a variously degenerated matrix. The comprehensive study allows to hypothesize the train of events leading, over the years, to the gradual transformation and degeneration of the larval form Echinococcus granulosus in the human liver.

A histochemical study on the hydatid cyst and electron microscopy of the hydatid sand of Echinococcus granulosus

The histochemistry of the hydatid cyst wall of E. granulosus from goat and sheep were studied. The cyst wall contains a carbohydrate-protein substrate complex, collagen and possibly calcium. Calcium is also reported in protoscolices of hydatid sand. Tegumental projections on free brood capsules and protoscolices were viewed by scanning electron microscope (SEM) and the tegument of protoscolices was revealed by transmission electron microscopy (TEM).

Could ivermectin have a synergic effect with albendazole in hydatidosis therapy?

The efficacy of a combination of ivermectin (IVM) and albendazole (ABZ) used as a chemoprophylactic treatment and as treatment of secondary hydatidosis is described for the first time. IVM treatment alone was not effective against Echinococcus granulosus, either when the protoscolices were recently inoculated or when they had developed to the metacestode stage. However, the efficacy of IVM and ABZ when used in combination as a prophylactic treatment was 95.72% and 87% with respect to the number and the wet weight of cysts, respectively. These results were higher than in the treatment of secondary hydatidosis, which were 44.8% and 45.26%, respectively. The ultrastructural changes in the germinal layer of the cysts after the treatments are also described.

Could ivermectin have a synergic effect with albendazole in hydatidosis therapy?

The efficacy of ivermectin (IVM) alone, albendazole (ABZ) alone and a combination of both (IVM + ABZ) against Echinococcus granulosus protoscolices was studied by means of in vitro incubation. The maximum protoscolicidal effect was detected when we used IVM+ABZ in combination. In this case, protoscolex viability dropped to 35% in comparison with 50% for IVM alone and 82.5% with ABZ alone 18 days post-incubation. Only the protoscolices incubated with IVM + ABZ did not develop into cysts following their inoculation into mice. The changes in ultrastructure induced in the protoscolices after the different drug incubations are also described. The incubation of cysts with IVM and IVM + ABZ shows that IVM + ABZ in combination is more effective than IVM alone as only when we incubated the cysts with IVM + ABZ did they completely lose their infectivity to mice. This occurred after only 10 days post-incubation. Cellular alterations were also more marked with IVM+ABZ incubations with: (1) the presence of residual bodies, (2) numerous lipids droplets and (3) vacuoles in the cytoplasm of cytons. However, the truncated microtriches and the nuclei remained unaltered after 10 days.

Relationship between the efficacy of praziquantel treatment and the cystic differentiation in vivo of Echinococcus granulosus metacestode

The cyst differentiation of protoscolices inoculated in NMRI mice was studied in detail. Although the laminated layer began its formation at 21 days post-infection (p.i.), we could not identify this structure in all parasites until 34 days p.i.. At 34 days p.i., all protoscolices were transformed into the metacestode stage. Subsequently, the efficacy of praziquantel (PZ) was studied in different stages of development of the parasite. We have found a different PZ susceptibility in both earlier stages and well-developed cyst. PZ treatment exhibited a high efficacy at the beginning of cyst differentiation and a zero efficacy in the mature metacestode when the cystic layers were totally developed. The relationship between the tegumental ultrastructural changes occurring during the vesicular evolution of protoscolices in NMRI mice and the efficacy of PZ treatment is discussed in the present study.

Depolarization of the tegument precedes morphological alterations in Echinococcus granulosus protoscoleces incubated with ivermectin

The nematocidal activity of ivermectin (IVM) largely arises from its activity as a potent agonist of muscular and neuronal glutamate-gated chloride channels. A cestocidal effect has also been suggested following in vitro treatments, but the molecular basis of this activity is not clear. We studied the effect of IVM on the metacestode stage of the tapeworm Echinococcus granulosus by assessing the viability, ultrastructure, and tegumental membrane potential as a function of drug concentration and incubation time. Concentrations of 0.1 and 1.0 microg/ml of IVM had no effect on any of these three parameters for up to 6 days of treatment. A concentration of 10 microg/ml, however, elicited a sequence of alterations that started with a approximately 20-mV depolarization of the tegumental membrane, and was followed by rostellar disorganization, rigid paralysis and, eventually, loss of viability. It is likely that the IVM-induced depolarization of the tegument acts as the signal that initiates the cascade of degenerative processes that leads to the parasite's death. This would place the tegument as the primary target of action of IVM on cestodes. As an appropriate chemotherapy for the hydatid disease is still lacking, the cestocidal effect of IVM reported here is worth considering.

In vitro effects of isoprinosine and a dipeptide methyl ester on Echinococcus multilocularis protoscoleces

A protoscoleces/vesicles in vitro maintenance test with assessment of viability by eosin exclusion was used to evaluate the quantitative and qualitative activities of isoprinosine, its active component inosine and the dipeptide methylester L-Phe-Phe-OMe on isolated protoscoleces of Echinococcus multilocularis for 24 and 48 h. Isoprinosine and inosine showed dose- and time-dependent activity, the latter displaying a more rapid effect than the former. A high activity was shown with L-Phe-Phe-OMe, when compared to praziquantel. Ultrastructural alterations were much more striking with L-Phe-Phe-OMe, with an effect similar to that of praziquantel, whereas the chemotherapeutic activity of inosine and isoprinosine appeared to be directed against a metabolic target, with a lethal effect not immediately visible at the ultrastructural level. Thus, the previously reported in vivo activities of these drugs result largely from a direct effect on the parasite.

Echinococcus multilocularis alkaline phosphatase as a marker for metacestode damage induced by in vitro drug treatment with albendazole sulfoxide and albendazole sulfone

Alveolar echinococcosis (AE) is caused by the metacestode stage of the fox tapeworm Echinococcus multilocularis. The disease affects the human liver and occasionally other organs and is fatal if treatment is unsuccessful. The present chemotherapy of AE is based on the administration of benzimidazole carbamate derivatives, such as mebendazole and albendazole. Albendazole treatment has been found to be ineffective in some cases, parasitostatic rather than parasiticidal, and the recurrence rate is rather high. Therefore, chemotherapy usually involves the lifelong uptake of massive doses of albendazole and new treatment options are urgently needed. In order to avoid costly and time-consuming animal experimentation, a first step in searching for novel parasiticidal compounds could be the in vitro drug screening of novel compounds by employing metacestode cultivation. However, presently used techniques (e.g., transmission electron microscopy) for determination of parasite viability involve costly equipment and time-consuming preparation of rather large amounts of parasite material. We therefore searched for a parasite marker which can be easily traced and the presence or absence of which is indicative of parasite viability. In this study we show that the increase of E. multilocularis alkaline phosphatase activity in culture supernatants during in vitro drug treatment with albendazole derivatives correlates with the progressive degeneration and destruction of the metacestode tissue. The inexpensive and rapid assay presented here will serve as an ideal tool for performing first-round in vitro tests on the efficacy of a large number of antiparasitic compounds.

Chemoprophylactic praziquantel treatment in experimental hydatidosis

In the present study, new data on the chemoprophylactic treatment of experimental hydatid disease with praziquantel are presented. In vivo studies have been performed reducing the treatment to 1 and 2 months. NMRI female mice inoculated with protoscolices of Echinococcus granulosus were treated with praziquantel 48 h p.i. at a dose of 600 mg/kg, 5 days a week for 1 or 2 months. After 4 months p.i. the animals were killed, and the cysts obtained were counted, weighed and processed for observations by means of transmission electron microscopy. Both wet weight and number of hyaline cysts found in treated mice were significantly lower than those found in control groups in both experiments (1 and 2 months of treatment), obtaining a high efficacy in all cases. Moreover, severe ultrastructural damage in the treated cysts was seen compared to the control cysts. The reduction in treatment time lays the basis for an important advance in the control and prevention of hydatidosis.

Praziquantel and albendazole in the combined treatment of experimental hydatid disease

The combination of praziquantel and albendazole (PZ + ABZ) used in the present study demonstrated an efficacy of 100% when used as chemoprophylactic treatment because no viable hydatid cysts developed after mice had been injected with protoscolices. However, when the PZ + ABZ combination was used for the treatment of 4-month secondary experimental hydatidosis, no significant difference was found between the control and treated mice, although severe damage to the cyst ultrastructure of the treated mice was observed.

Characterization of the laminated layer of in vitro cultivated Echinococcus vogeli metacestodes

The metacestode (larval) stages of the cestode parasites Echinococcus vogeli and E. multilocularis were isolated from the peritoneal cavity of experimentally infected C57BL/6 mice and were cultured in vitro for a period of up to 4 mo under conditions normally applied for the in vitro cultivation of E. multilocularis metacestodes. In contrast to E. multilocularis, E. vogeli did not exhibit extensive exogenous budding and proliferation but increased in size with a final diameter of up to 10 mm. Most metacestodes contained protoscoleces, singly or in groups, either associated with brood capsules or growing directly out of the germinal layer. Each individual metacestode was covered by an acellular translucent laminated layer that was considerably thicker than the laminated layer of E. multilocularis metacestodes. The ultrastructural characteristics, protein content, and carbohydrate composition of the laminated layer of in vitro cultivated E. vogeli and E. multilocularis were assessed using transmission electron microscopy, lectin fluorescence labeling, and lectin blotting assays. The laminated layer of E. vogeli is, as previously described for E. multilocularis metacestodes, largely composed of N-acetyl-beta-D-galactosaminyl residues and alpha- and beta-D-galactosyl residues, as well as of the core structure of O-linked carbohydrate chains, N-acetylgalactosamine-beta-1,3-galactose. However, in contrast to E. multilocularis, N-linked glycopeptides and alpha-D-mannosyl and/or glucosyl residues were also associated with the laminated layer of E. vogeli. The laminated layer from both species was isolated from in vitro cultivated metacestodes, and the purified fractions were comparatively analyzed. The protein:carbohydrate ratio (1:1) was similar in both parasites; however, the protein banding pattern obtained by silver staining following sodium dodecyl sulfate polyacrylamide gel electrophoresis suggested intrinsic differences in protein composition. A polyclonal antiserum raised against the E. multilocularis laminated layer and a monoclonal antibody, G11, directed against the major E. multilocularis laminated layer antigen Em2 did not cross-react with E. vogeli, indicating distinct compositional and antigenic differences between these 2 parasites.

In vitro effect of praziquantel and albendazole combination therapy on the larval stage of Echinococcus granulosus

Protoscolices of Echinococcus granulosus were incubated in vitro with praziquantel (PZ), albendazole (ABZ), or a combination of both (PZ + ABZ). PZ and ABZ displayed slower protoscolicidal activity when applied separately than when used in combination. Despite the low PZ + ABZ concentrations used, protoscolex viability dropped rapidly (within 15 days). At this time, cysts did not develop following their inoculation into mice. The ultrastructural changes induced in the protoscolices by PZ + ABZ were (a) the loss of sucker concavity, (b tegumental contraction of the soma region, (c) the formation of digitiform tegumental extensions, (d) destruction of the tegument, and (e) the degeneration of parenchyma cells as reflected by the presence of numerous lamellar bodies. The PZ + ABZ treatment was effective only against small cysts, which had collapsed at 10 days postinoculation (p.i.). This treatment caused the following alterations: (a) loss of cyst turgidity at 6 days p.i.; (b) separation of the laminated and germinal layers; (c) loss of microtriches; (d) the appearance of numerous lipid droplets in the inner region of the germinal layer, (e) vacuolation of the cyton cytoplasm; and (f) the formation of abundant autophagosomes, which finally led to loss of the integrity of the germinal layer.

Immunofluorescent localization of intermediate filaments (IFs) in helminths using anti-mammalian IFs monoclonal antibody

Intermediate filaments (IFs) make up the cytoskeleton of most eukaryotic cells. In vertebrates, a number of IF proteins have been identified, showing distributions unique to tissue or cell type. Information on helminth IFs is limited to some nematode species. To observe immunofluorescent localization of IFs in helminth tissues, we selected a murine hybridoma clone producing IgM antibody to multiple types of mammalian IF proteins and examined cross-reactivity to helminth proteins. The selected monoclonal antibody (HUSM-9) cross-reacted well with IFs from nematode species such as Toxocara canis, Dirofilaria immitis, Anisakis simplex, and Trichinella britovi; strong immunofluorescence on cryostat sections was detected in the hypodermis, cords, body muscle, smooth muscle of the uterus, and other epithelial structures. In platyhelminths, i.e., adult Schistosoma mansoni, larval Taenia taeniaeformis, adult Taenia crassiceps, and Echinococcus multilocularis protoscolex, the reactivity was weaker than in nematodes, and localized in the body wall muscle and subtegumental tissue. Western blotting of 8 M urea extracts of parasites with the antibody detected a pair of clear bands in nematodes but not in S. mansoni or the cestodes. These results might be explained by sparse distribution of IFs in platyhelminths, or low affinity of the used antibody to platyhelminth IF proteins, or both.

High molecular mass glycans are major structural elements associated with the laminated layer of in vitro cultivated Echinococcus multilocularis metacestodes

The laminated layer of the larval stage (metacestode) of the cestode parasite Echinococcus multilocularis is composed largely of carbohydrates, which form a tight microfibrillar meshwork around the entire metacestode. Since this laminated layer is the only parasite structure which is in constant contact with host immune and non-immune cells, and appears largely resistant to physiological and immunological reactions of the host, it most likely carries out important functions with regard to host-parasite interactions. In infected hosts, the metacestode is usually concentrically covered by host connective tissue cells and large amounts of collagen, causing a dense scar-like fibrosis, and it is likely that host-derived components are incorporated into the laminated layer at the host-parasite interface. Therefore, in order to obtain information on the molecular composition of this structure, we used parasite larvae which were generated through in vitro cultivation and thus were largely devoid of interfering host components. Lectin fluorescence on section-labelling of metacestodes embedded in LR-White suggested that the laminated layer is largely composed of N-acetyl-beta-D-galactosaminyl, and alpha- and beta-D-galactosyl residues, as well as of the core structure of O-linked carbohydrate chains, N-acetylgalactosamine-beta-1.3-galactose, while N-linked glycopeptides and alpha-D-mannosyl residues and/or glucosyl residues were found mainly within the germinal layer, and within the cellular mass and the surface of developing protoscoleces. Lectin-gold EM confirmed these findings. The laminated layer was isolated from in vitro cultivated metacestodes by urea extraction, and the ultrastructure of the purified laminated layer was assessed comparatively with respect to the laminated layer of intact parasites. The glycan composition was determined using SDS-PAGE and lectin blotting. This work has laid the basis for a more detailed dissection of the molecular composition of the laminated layer.

Echinococcus granulosus: praziquantel treatment against the metacestode stage

The efficacy of praziquantel against the metacestode of Echinococcus granulosus was studied by means of in vitro incubations or in vivo experiments. The results of in vitro incubations indicated that the effectiveness of praziquantel was higher when the parasite material comprised cysts from cyst masses than in the case of intact cysts that retained their adventitial layer. Ultrastructural alterations in the germinal layer of collapsed cysts incubated in vitro were detected. The results obtained in mice after 4 months of treatment demonstrated no significant difference between the control and treated groups with regard to the number and wet weight of developed cysts. However, ultrastructural alterations were detected in the cyst tissue that were similar to those described in the in vitro experiment. In contrast, the effect of chemoprophylaxis on the number and the wet weight of developed cysts was extremely significant as compared with the control value, the efficacy being 99.41% and 98.32%, respectively. Moreover, ultrastructural observations of the cyst tissue revealed loss of its integrity, and no intact cyton was observed in the germinal layer of the developed cyst.

Efficacies of albendazole sulfoxide and albendazole sulfone against In vitro-cultivated Echinococcus multilocularis metacestodes

The metacestode stage of Echinococcus multilocularis is the causative agent of alveolar echinococcosis (AE), a parasitic disease affecting the liver, with occasional metastasis into other organs. Benzimidazole carbamate derivatives such as mebendazole and albendazole are currently used for chemotherapeutic treatment of AE. Albendazole is poorly resorbed and is metabolically converted to its main metabolite albendazole sulfoxide, which is believed to be the active component, and further to albendazole sulfone. Chemotherapy with albendazole has been shown to have a parasitostatic rather than a parasitocidal effect; it is not effective in all cases, and the recurrence rate is rather high once chemotherapy is stopped. Thus, development of new means of chemotherapy of AE is needed. This could include modifications of benzimidazoles and elucidiation of the respective biological pathways. In this study we performed in vitro drug treatment of E. multilocularis metacestodes with albendazole sulfoxide and albendazole sulfone. High-performance liquid chromatography analysis of vesicle fluids showed that the drugs were taken up rapidly by the parasite. Transmission electron microscopic investigation of parasite tissues and nuclear magnetic resonance spectroscopy of vesicle fluids demonstrated that albendazole sulfoxide and albendazole sulfone had similar effects with respect to parasite ultrastructure and changes in metabolites in vesicle fluids. This study shows that the in vitro cultivation model presented here provides an ideal first-round test system for screening of antiparasite drugs.

Ultrastructural localization of an Echinococcus granulosus laminin-binding protein

Murine antibodies, raised against a purified recombinant 30 kDa laminin-binding protein from Echinococcus granulosus, were used to investigate the tissue distribution of the native protein in protoscoleces and brood capsules. Immunofluorescence, in combination with confocal microscopy, revealed that the protein was distributed in small annular foci near the peripheral regions of the protoscoleces. Immunoelectron microscopy of thawed cryosections demonstrated that the laminin-binding protein was present in the cytoplasm of tegumentary cytons and myocytons, but not in cells of the excretory system. The protein was associated with amorphous regions of the cytoplasm, and was not expressed at the surfaces of cells. This distribution resembles those of other invertebrate laminin-binding proteins, which are thought to act in the cell cycle and cell proliferation events. A low degree of label was consistently detected in extracellular matrices of the protoscolex.

Reappraisal of vesicular types in the syncytial tegument of the Echinococcus granulosus protoscolex

The structure, abundance, and distribution of tegumentary vesicles was compared among Echinococcus granulosus protoscoleces that had been prepared for electron microscopy using four processing schedules: a conventional method, alternative fixations using uranyl acetate or osmium tetroxide-potassium ferricyanide, and a freeze-substitution method. Four morphologically distinct types of vesicles were found in the somal region. The morphology of the first form, with moderately electron-opaque contents, and the second form, with similar size and shape but containing an electron-opaque core, varied little among the preparation methods. Two additional forms of vesicles, with characteristic intensely electron-opaque contents, were revealed only after freeze-substitution. These elongate vesicles were also found in the scolex tegument where they were most conspicuous, and appeared markedly increased in number after freeze-substitution. Large, spherical vesicles with an electron-lucent core embedded in a dense matrix of fibrillar strands were the dominant vesicle forms in the scolex region after all methods of preparation. Fixation by osmium tetroxide-potassium ferricyanide revealed the presence of spherical vesicles with amorphous electron-opaque contents and a few inclusions. This form of vesicle was also observed after freeze-substitution, but the inclusions in the vesicular lumen were more numerous. The variation in the distribution of vesicle forms among the body regions strongly implies a variety of vesicle functions. In addition, our observations suggest that comparative studies of different fixative methods are necessary to demonstrate the detailed vesicular morphology of the tegument of E. granulosus and other cestodes.

Echinococcus multilocularis metacestodes: immunological and immunocytochemical analysis of the relationships between alkaline phosphatase and the Em2 antigen

Echinococcus multilocularis metacestodes possess an alkaline phosphatase (EmAP) which has been extensively characterized at the biochemical level in previous studies. The apparent molecular weight of the enzyme monomer and its isoelectric point matched those originally described for the Em2 antigen, a reference antigen currently used for the immunodiagnosis of E. multilocularis infection. These observations raised questions about the molecular relationship between the two molecules. In order to investigate the relations between EmAP and the Em2 antigen, immunoblotting and ELISA were carried out using polyclonal and monoclonal antibodies directed against EmAP and the Em2 antigen, respectively. In addition, the localization of EmAP and the Em2 antigen was compared by immunofluorescence and immunogold electron microscopy in in vitro-generated E. multilocularis metacestodes. The results show that common epitopes between EmAP and Em2 exist, which are predominantly of a peptidic nature. Both antigens are localized in an acellular parasite structure, the laminated layer, with additional locations for the EmAP on the glycocalyx and in the central region of invaginated protoscoleces. These results suggest a putative functional relationship between the two antigens and that Em2 could originate from EmAP.

Increases in the effects of albendazole on Echinococcus multilocularis metacestodes by the dipeptide methyl ester (Phe-Phe-OMe)

Three months after infection with Echinococcus multilocularis, Mongolian gerbils were given either the dipeptide methyl ester (Phe-Phe-OMe) or a combination of Phe-Phe-OMe plus albendazole to treat alveolar echinococcosis. Each drug was given orally at the daily dose of 50 mg/kg of body weight following various administration regimens. Histologic and ultrastructural studies of parasites recovered from infected gerbil tissues showed that the dipeptide methyl ester increases the effect of albendazole.

The ultrastructural localization of Echinococcus granulosus antigen 5

Murine monoclonal and polyclonal antisera, raised against the 38 kDa subunit of Echinococcus granulosus antigen 5, were used to investigate the tissue distribution of the antigen in hydatid cysts. Immunoreactivity was visualized by indirect immunofluorescence on whole protoscoleces, and ultrastructural immunocytochemistry utilizing colloidal gold-based labelling procedures on unsectioned and cryosectioned brood capsules and protoscoleces. In protoscoleces, the 38 kDa subunit of antigen 5 was localized at the interface of parenchymal cells and associated extracellular matrices, as well as along the interface of the tegumentary syncytium in the somal region and its basal matrix. Cytoplasmic labelling of parenchymal cells was rare; when observed, it was associated with vesicles and membranes in cytoplasmic extensions of parenchymal cells. In brood capsules, the antigen was associated with the external face of the plasma of degenerating parenchymal cells. The 38 kDa subunit occurs along the extracellular face of cell membranes, suggesting that antigen 5 is either a component of the membranes or associated extracellular matrices.

Development of chemotherapeutic model for the in vitro screening of drugs against Echinoccus granulosus cysts: the effects of an albendazole-albendazole sulphoxide combination

This paper describes a novel experimental model for the screening of putative drugs against the metacestode stage of E. granulosus using hydatid cysts derived from in vitro culture of protoscoleces. The effects of an ABZ+ABZ.SO combination against cultured and murine cysts were studied with this in vitro model system. This treatment produced loss of turgidity of the cultured cysts in less time than in the murine cysts but the ultrastructural tissue damage observed in both cultured and murine cysts was similar. The ultrastructural changes induced by ABZ+ABZ.SO were: (i) vacuolation of the distal cytoplasm that extended to the tegumentary cells of the germinal membrane; (ii) increased number of mitochondria; (iii) partial loss of microtriches; (iv) increased number of autophagosomes; and (v) an increase in lipid deposits.

The scanning electron microscopy of scolices in a case of hydatid cyst from human liver

The scanning electron microscopic (SEM) features of hydatid scolices from a case of hydatid disease of the liver are described. The scolex when fully everted has a double circle of hooklets which occupy a large area of the parasite. The hooklets are inserted into the rostellum with one row of hooklets overlapping the other. Each hooklet is about 20 to 40 um long, has a basic round structure sharp at the distal end and broadens as it curves towards the point of insertion at the rostellum, where 2 blunt projections correspond to the 2 annular bundles of muscle fibres at the orifice of the scolex. The function of the hooklets is not fully understood but they are possibly used for anchorage and/or for the purpose of propulsion in a fluid medium by the act of invagination and evagination of the hooklets.

Immunology and morphology studies on the proliferation of in vitro cultivated Echinococcus multilocularis metacestodes

The larval stage of Echinococcus multilocularis causes alveolar echinococcosis (AE) in various mammals, including humans. Traditionally metacestodes are maintained in the laboratory by serial transplantation passages into susceptible animals such as mice or gerbils. However, in animal models it has always been difficult to draw definite conclusions about the factors modulating metacestode differentiation, and investigations on gene expression and respective regulation have been hampered by the complexicity of the host-parasite interplay. This paper describes the maintenance and proliferation of E. multilocularis metacestodes as well as the formation of protoscolices in a chemically defined medium devoid of host influence. The interactive role of a heterologous human cell line (CACO2) in the in vitro development of metacestodes was also assessed. The morphology and ultrastructure of in vitro-generated metacestodes was studied using scanning (SEM) and transmission electron microscopy (TEM). Different cultivation procedures were analyzed in terms of expression of B- and T-cell epitopes and of the relevant laminated layer-antigen Em2; the exact localization of this antigen was further demonstrated by immunogold electron microscopy.

Effects of Isoprinosine on Echinococcus multilocularis and E. granulosus metacestodes

An in vivo study of the effect of Isoprinosine on Echinococcus multilocularis and E. granulosus metacestodes (Cestoda) was performed. Short- and long-term treatments with different doses were tested in experimental hosts: jirds for E. multilocularis and mice for E. granulosus. Modifications in the weight of animals as well as macroscopical and ultrastructural aspects were registered for each animal group. The results obtained showed a considerable ultrastructural alteration in E. multilocularis metacestodes after short-term treatment with the highest dose, and the tissue transplants were negative. In E. granulosus cysts the ultrastructural damage was also very important and its severity increased as the dose was raised. For the two parasites, the macroscopical aspect and weight of the lesions were profoundly changed.

Anti-tubulin immunohistochemistry study of Echinococcus granulosus protoscolices incubated with albendazole and albendazole sulphoxide in vitro

Tubulin content was immunohistochemically studied in Echinococcus granulosus protoscolices incubated with albendazole and albendazole sulphoxide alone or in combination. Tubulin immunoreactivity was very patent in the control protoscolices and was mainly located in the sucker region and the invagination channel of protoscolices. Treated protoscolices always showed less immunoreactivity than did control protoscolices. We concluded that albendazole and its metabolite albendazole sulphoxide produce tubulin alterations in E. granulosus protoscolices.

Echinococcus granulosus: the mechanism of oncosphere lysis by sheep complement and antibody

A heat-labile component of normal sheep serum (56 degrees C for 30 min but not 50 degrees C for 30 min) was able to lyse oncospheres in vitro. The degree of effect, and the proportion of oncospheres lysed, was related to the concentration of normal unheated sheep serum complement, or other sources of complement (rabbit, mouse) in the culture. Lower concentrations were required for lysis if the culture serum was obtained from sheep immune to E. granulosus infection. Heat inactivation of normal or immune sheep serum removed any lytic ability. No lysis occurred in any concentration of unheated foetal lamb serum. However, unheated foetal lamb serum was able to restore the lytic effect to heated normal or immune serum. This suggests that lysis in both immune and normal serum is antibody-dependent and complement-mediated. The lysis in normal serum would appear to be due to natural cross-reacting antibodies that can fix complement at the oncosphere surface. The complement lesion resulted in damage to the plasma membrane. This then peeled back, predisposing the oncosphere to osmotic destruction. The use of bleach to dissolve the embryophore caused damage to the plasma membrane similar to that caused by complement. Developing metacestodes at 3 days of age in vitro in immune serum were susceptible to the addition of complement at that time.

Ultrastructure of oncosphere and early stages of metacestode development of Echinococcus granulosus

The ultrastructure of the oncospheres and developing metacestodes in vitro of Echinococcus granulosus was studied with emphasis on the origin of the laminated layer. The activated oncospheres measured 28 microns (S.D. = 1.83), and by day 5 of in vitro culture the metacestodes attained diameters up to 52 microns (S.D. = 2.66). The oncospheral plasma membrane of the tegument appeared to be formed by a microtubular cytoskeleton arranged in a predetermined pattern. By day 2 there were three main types of vesicles in the perikaryon: Vd, Vg1 and Vg2. Vesicles appeared to be synthesized in the perikaryon and continuously transported to the periphery, where the Vd vesicles could contribute to the ground substance of the syncytial tegument. We suggest that the Vg1 and Vg2 vesicles contribute to the laminated layer where, by day 5, they were seen in increased density and forming aggregations on the outer border.

Immunocytochemical localization of serotonin (5-HT) in the nervous system of the hydatid organism, Echinococcus granulosus (Cestoda, Cyclophyllidea)

The localization and distribution of the serotoninergic components of the nervous system in the hydatid organism, Echinococcus granulosus, were determined by immunocytochemical techniques in conjunction with confocal scanning laser microscopy (CSLM). The distribution of serotonin immunoreactivity (IR) paralleled that previously described for cholinesterase activity, although it was more widespread. Nerve cell bodies and nerve fibres immunoreactive for 5-HT were present throughout the central nervous system (CNS), occurring in the paired lateral, posterior lateral and rostellar ganglia, their connecting commissures and nerve rings in the scolex and in the ten longitudinal nerve cords that run posteriorly throughout the body of the worm. A large population of nerve cell bodies was associated with the lateral nerve cords. In the peripheral nervous system (PNS), immunoreactive nerve fibres occurred in well-developed nerve plexuses innervating the somatic musculature and the musculature of the rostellum and suckers. The genital atrium and associated reproductive ducts were richly innervated with serotoninergic nerve cell bodies and nerve fibres.

Effects of benzimidazole compounds on mice infected with secondary cysts of Echinococcus granulosus

The effects of mebendazole (Meb), albendazole (Alb) and albendazole sulfoxide (AlbSO) on metacestodes of Echinococcus granulosus have been studied. The results show that Meb and Alb exhibit less effect on protoscoleces in vitro, but in vivo the protoscolicidal effect of Meb is higher than that of Alb. Both Meb and Alb are efficacious in the treatment of mice infected with secondary cysts of E. granulosus. In terms of the minimal effective dose required, the occurrence of collapsed and shrunk cysts after treatment, the drug-induced damage on the germinal layer and the relationship between the drug content in the cyst wall and the damage of germinal layer, the effect of Meb on metacestodes of E. granulosus is higher than that of Alb. The results also indicated that lower drug absorption rate and thickening of the adventitia during longer disease course are the two major factors affecting the efficacy of Meb and Alb, hence suggesting that increase of Meb absorption may be expected to raise the therapeutic effect of the drug. Finally, Alb is not only metabolized to AlbSo and AlbSP in vivo, but also metabolized by the cysts exposed to Alb in vitro. Experimental chemotherapy showed that AlbSO is the major effective metabolite of Alb, and its curative dose is only one half of the parent compound.

Development of truncated microtriches in Echinococcus granulosus protoscolices

The development of truncated microtriches in the somatic region of both (a) protoscolices incubated in vitro with two different drugs, i.e. ivermectin or a combination of albendazole and albendazole sulphoxide, and (b) protoscolices removed from hydatid cysts in humans treated with albendazole for 1.5 months is described. Our findings seem to indicate that the development of microtriches is either an indirect effect of treatment with anthelmintics or a possible response to other, as yet unidentified, adverse conditions.

Echinococcus multilocularis: in vitro interactions between protoscolices and Kupffer cells

Echinococcus multilocularis protoscolices collected from experimentally infected jirds were incubated for 2 weeks in rat hepatic cell cultures cocultivated with or without feeder cells (BALB/c 3T3 and IAR 20). Scanning and transmission electron microscopy studies were performed during the course of the culture period. Kupffer cells (Kc) were seen adhering to the anterior and posterior ends of the protoscolices. Some protoscolices were fixed to the cell monolayer by a cluster of Kc adhering to the posterior end of the parasite. These cells were phagocytosing the glycocalyx and the electron-dense distal end of the microthrix of the protoscolex tegument. An alteration in the superficial tegumental cytoplasm with extensive mitochondrial damage was also noted. The properties expressed by Kc against protoscolices in vitro might also be relevant for proliferation of metacestodes in vivo.

The effects of albendazole and albendazole sulphoxide combination-therapy on Echinococcus granulosus in vitro

Protoscoleces of Echinococcus granulosus were incubated in vitro with decreasing concentrations of either albendazole (ABZ) or albendazole sulphoxide (ABZ.SO) (50, 10, 1 and 0.1 micrograms ml-1), and in combination. Viability was assessed by the methylene blue exclusion test and establishment of infection in mice. Protoscolex ultrastructure was determined by means of transmission and scanning electron microscopy. ABZ and ABZ.SO, when used separately had protoscolicidal activity after a longer incubation period (30 days) than when used as combined compounds. When incubated in the presence of ABZ + ABZ.SO, protoscolex viability dropped rapidly. That is, protoscoleces were all non-viable at 12 days of exposure, with no cyst developing following their inoculation into mice. The ultrastructural changes induced by ABZ or ABZ.SO alone, were: (a) rostellar disorganization, (b) formation of numerous blebs on the tegument, (c) loss of the microtriches, (d) increased vesiculation within the tegumentary cytons together, (e) an increase in lipid deposits and (f) depletion of glycogen reserves. After incubation with combined ABZ and ABZ.SO the tegument contained numerous blebs which became detached, leaving debris only, some intact nuclei being discernible in the protoscolex parenchyma.

Enhanced larval cyst growth of Echinococcus multilocularis in praziquantel-treated jirds (Meriones unguiculatus)

Jirds (Meriones unguiculatus) inoculated intraperitoneally with cystic material of Echinococcus multilocularis were given daily oral treatments of praziquantel at 300 mg/kg of body weight (bw) or dimethyl sulfoxide vehicle for five-day treatment regimens starting at 29 days postinoculation (PI) up to 69 days PI. At 39 or 49 days PI, the growth of the larval cystic mass (LCM) in jirds following a single or two five-day treatment regimens was significantly enhanced (P < 0.05) by 129.0% (2.3-fold) or 102.9% (2.0-fold), respectively. At 59 or 69 days PI following three or four five-day treatments with praziquantel, LCM growth was enhanced by 47.8% (1.5-fold) and 44.1% (1.4-fold), respectively, but was no longer significantly different than that in control jirds. A single five-day treatment on 29-33 days PI (with necropsy at 69 days PI) significantly enhanced the growth of the LCM by 87.6% (1.9-fold). Parasites from praziquantel treatment regimens examined ultrastructurally showed consistent damage to the germinal membrane evidenced by vacuolization and rupture of syncytial cytoplasm, rupture and coalescence of the electron-lucent vesicles just below the microvilli of the tegumental surface, and swelling and rounding of mitochondria. At 39 days PI, increased blebbing of the germinal membrane into the lumen of the LCM in praziquantel-treated animals was observed by scanning electron microscopy. The treatment-induced blebs were identified as nucleated germinal cells by transmission electron microscopy and appeared to be responsible for metastasis and enhanced growth of the LCM. Although praziquantel damaged the ultrastructural integrity of the LCM, treatment failed to inhibit larval cyst growth or protoscolex development.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructural localization of major hydatid fluid antigens in brood capsules and protoscoleces of Echinococcus granulosus of human origin

Monospecific rabbit antisera obtained through experimental immunization with previously purified proteins were used in the ultrastructural localization of two hydatid fluid antigens, in brood capsules and protoscoleces of Echinococcus granulosus of human origin. The antigen-antibody reaction was revealed by a colloidal gold based method. Reaction was evident in the connective region of the germinal membrane and in the parenchyma of the protoscoleces. Both antigen 5 and antigen B were located in the interstitial material between the parenchymal cells and precisely associated with disorganized areas. The brood capsule wall and the brood capsule contents, the tegument of the protoscoleces, the parenchymal cells, the muscle cells, the calcareous corpuscles and the hooks did not contain antigen 5 or antigen B. Label was not observed in the lumen of the collecting ducts or in the flame cells, although antigen 5 was evident in the periluminal cytoplasm. The origin of the antigens and their release are discussed.

[The use of low-frequency ultrasound in the surgical treatment of pulmonary echinococcosis]

A convincing evidence is given that the low-frequency ultrasound (26.4-26.6 kHz) has pronounced parasiticidal and bactericidal effects and can completely replace the drugs commonly used for disinfection. The low-frequency ultrasound used for treatment of the parasitic cyst bed allows the indication for organ preserving operations to be wider, the complicated forms of the disease included.

[Right-sided hemihepatectomy in echinococcosis of the liver in pregnancy]

The treatment of symptomatic echinococcal disease of the liver during pregnancy is a rare, but difficult problem. A 42 year old, pregnant woman with obstructive jaundice and acute cholangitis due to extensive echinococcus cysticus infection of the right hepatic lobe is presented. A formal, right hemihepatectomy was successfully performed.

Synthesis of propargylic alcohols and biological effects on Echinococcus multilocularis metacestodes

This study describes the synthesis of propargylic alcohols derived from isatin and their biochemical and morphological effects on Echinococcus multilocularis metacestodes in Meriones unguiculatus. Propargylic alcohols decreased the alkaline phosphatase and the lactate dehydrogenase activities of the metacestode selectively. The most effective compound, 1b, decreased the lactate dehydrogenase enzymatic activity, and the glucose concentration in the parasite increased, whereas the glycogen content was partially decreased. Furthermore, the ultrastructure study revealed several damages. The host-parasite relationships are very important in the intrahepatic cestodes as shown by the biochemical side effects observed in the host's liver during the treatment. An in vitro enzymatic study was performed with alcohols 1b and 1c.

Anthelmintic effects of cyclosporin A on protoscoleces and secondary hydatid cysts of Echinococcus granulosus in the mouse

Cyclosporin A (CsA), employed primarily as an immunosuppressant during the management of organ and graft transplants, exhibits anthelmintic properties. However, its efficacy against tapeworm infections in laboratory models is variable. A preliminary investigation has been undertaken to assess the action of CsA on the establishment and growth of protoscoleces and secondary hydatid cysts of ovine Echinococcus granulosus in mice. Administration of CsA in five consecutive daily doses, beginning 2 days prior to infection, resulted in significant reduction in cyst establishment (measured in terms of cyst masses, cyst numbers and cyst wet weights), when mice were autopsied 20 weeks post-infection. None of these parameters were significantly reduced when the drug was administered 18 weeks post-infection, although wet weight decreased by 42%. Ultrastructural examination of the germinal membrane and laminated layer of late-treated E. granulosus revealed abnormalities in all cysts studied whereas control and early-treated hydatids were normal. A case is made for the consideration of a clinical use for CsA for post-operative control of secondary hydatidosis and its efficacy against hydatid cysts is discussed.

Echinococcus granulosus:isoprinosine treatment of the metacestode stage

The efficacy of short- and long-term treatments with Isoprinosine, an immunomodulatory compound, was studied in Echinococcus granulosus cysts developed in NMRI mice intraperitoneally infected with sheep pulmonary cysts. After treatment, a reduction in the size and number of cysts with macroscopic modifications was observed. The structural alterations included damage or destruction of the protoscoleces and partial destruction of the cyst wall, which predominated at the inner germinal layer level. The efficacy of this drug was evaluated after long-term and short-term treatment. Short-term treatment with a dose of 1 g/kg/day gave better results, with a loss of infectivity of the larval tissue. The well-tolerated long-term treatment with a dose of 2 g/kg/day showed the absence of toxicity of this compound. The survival time of treated animals was greater than that of untreated controls.

Cytology in the percutaneous treatment of hydatid cysts. A report of four cases

Four cases of percutaneous treatment of hydatid cysts are reported. Cytologic examination of the cyst fluid is important to confirm the diagnosis in patients who did not develop antibodies. Gomori stain gives the best results in identifying the three elements of a hydatid cyst: scolices, hooklets and laminated membranes. Moreover, staining for viability assessment gives information about the success of drug treatment.

Ultrastructure and microanalyses of the calcareous corpuscles of the protoscoleces of Echinococcus granulosus

The calcareous corpuscles of the protoscolex stage of Echinococcus granulosus are irregularly spherical or ovoid in shape and have a diameter ranging between 2 and 16 microns. The central region of immature corpuscles is composed of an electron-lucent matrix containing granular deposits and, in more mature corpuscles, paired membrane lamellae. Energy-dispersive X-ray microanalysis of sectioned immature corpuscles demonstrated calcium, magnesium and phosphorus, whilst a quantitative analysis indicated the presence of calcium and magnesium at 142.7 and 41.3 mg/g dry weight, respectively, and inorganic phosphate at 18.0 mg/g. Assuming that the anion is predominantly carbonate, the molar ratio of Ca:Mg:HPO4(2-):CO3(2-) is 1:0.48:0.08:1.41. X-ray diffraction patterns obtained from preparations of whole corpuscles indicated a poorly crystalline material including the mineral calcite. X-ray absorption near-edge spectra of corpuscles, taken over the phosphorus K edge, resembled those of brushite (CaHPO4.2H2O) and suggest that the phosphate, within the corpuscles, is present in an amorphous, hydrated form that could be readily solubilised and mobilised for the metabolic processes of the organism.

Studies on Echinococcus granulosus using the scanning electron microscope. II. The hooks

The morphology of the hooks of Echinococcus granulosus at the protoscolex level was studied by means of scanning electron microscopy. Hooks were uncovered in situ and also freed from the rostellum so as to study them in detail. There were two types of hooks: those of the upper row, which were larger and had a projecting, rounded stout guard, and those of the lower row, which were smaller and had a flattened guard. These and other differences in the morphology of the two types of hooks were studied and related to the differences in their function.

Studies on Echinococcus granulosus using the scanning electron microscope. I. Preparations of the parasite for infection of the final host

The development of the protoscoleces of Echinococcus granulosus was studied after chemical stimulation, which mimics that offered by the final host. This stimulation resulted in some morphological changes in the parasite and to its evagination. These changes prepare the parasite to infect the intestine of its final host. The external morphology of the protoscolex body and of the germinal layer of the cyst and brood capsule were studied using the scanning electron microscope (SEM). Findings were related to other studies using the transmission electron microscope (TEM). The morphology of the flame cell is described and four cases of teratogenesis are reported.