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PubMed1989

Autoradiographic study of the attrition of migrating schistosomula in the skin of mice. I. Mice immunized with highly X-irradiated Schistosoma mansoni cercariae.

The migratory pattern in naive mice of Schistosoma mansoni cercariae X-irradiated with OkR, 12kR, or 48rR has been investigated with compressed organ autoradiography. Three groups of 69 mice each were infected with 75Se-labelled cercariae. The skin at the site of infection, as well as the entire lungs and liver were removed from infected mice daily from 1-21d, on 24d, and on 28d; tissues were then processed for autoradiography. Autoradiographic analysis of migratory patterns showed that the schistosomula derived from nonattenuated cercariae passed quickly from the skin to the lungs and at a moderate rate from the lungs to the liver. Schistosomula derived from 12kR-irradiated cercariae were delayed in passing from the skin to the lungs and from the lungs to the liver, so that many remained in the lungs and died there, while only a few died in the skin or liver. Schistosomula derived from 48kR-irradiated cercariae remained mainly in the skin, rarely reached the lungs and were never found in the liver. This study indicates that immunization with 48kR-irradiated cercariae will cause no significant lesions in the lungs or liver.

Animals↗
PubMed1987

Host identification by Schistosoma japonicum cercariae.

Attachment, the first phase of host identification by Schistosoma japonicum cercariae, can occur in 2 different ways. Cercariae clinging to the water surface simply swing around and transfer to the host skin. Free-swimming cercariae behave like S. mansoni: upon touching a substrate, they switch from tailward to forward movement, swim in an arc, and attach to it with the penetration organ. Neither type of attachment is influenced by chemical, thermal, or specific mechanical stimuli from the host. The second phase, remaining on the host, requires a solid hydrophobic surface and seems to depend only on the cercaria's ability to cling to it. This phase is not influenced by chemical or thermal stimuli. The third phase, creeping across the host surface, is independent of chemical and mechanical stimuli. Cercariae migrate in thermal gradients to a preferred temperature of 37 +/- 3 C and then attempt to penetrate. Penetration, the fourth phase, was evoked by human skin surface lipids. The free fatty acid (FA) fraction was identified as exclusively stimulating components. Saturated FA's were effective at chain lengths between 10 and 14 carbon atoms (pH 7.0), and unsaturated FA's were effective at longer chains and their activity increased with increasing number of double bonds. Dog skin surface components did not stimulate cercarial penetration, which can be attributed to the lack of free FA's. A temperature of 32-40 C also stimulated penetration responses, which might be the main stimulus in animal hosts, whose skin surfaces contain no or only a few free FA's. FA's and heat evoked a transformation of cercarial tegument simultaneous with penetration behavior, making the organisms osmotically sensitive. The host identification of S. japonicum cercariae is very nonspecific compared with the differentiated host recognition of S. mansoni.

Adhesiveness↗
PubMedDate not supplied

[Adaptibility of Diplostomum cercariae in carp and the effect of a prior infestation].

Experiments on the infection of carp fry with cercariae of Diplostomum have shown that cercariae of Diplostomum spathaceum can penetrate crystalline lens of larvae of these fishes in three days after their hatching and that the adaptability of cercariae of D. paracaudum to carp is much higher than that of cercariae of D. spathaceum. After the first infection with cercariae a relative postinfectious immunity against infection with cercariae of this or close species of this genus arises in carp fry.

Adaptation, Physiological↗
PubMed1994

Schistosoma mansoni: the presence of schistosomule-like characteristics in irradiated cercariae.

Schistosoma mansoni (Puerto Rican strain) cercariae were exposed to 10, 20, 50, 100, 200, 300, 400 and 500 krad gamma radiation from 60Co gamma source. From 10-100 krad irradiation no differences could be found in the behaviour of the cercariae when compared to the controls. From 200-500 krad there was an increase in mortality as well as in the number of cercariae that shed their tails. The Con A binding studies also performed on cercariae radiated with up to 100 krad indicate a direct relationship between the number of cercariae that bind Con A and radiation dose. All live cercarial heads collected after radiation also bound Con A. It thus seems possible that irradiation may act as a stimulus for cercariae to transform to schistosomulae.

Animals↗
PubMed1993

Protective immunity in baboons vaccinated with a recombinant antigen or radiation-attenuated cercariae of Schistosoma mansoni is antibody-dependent.

Mice vaccinated with radiation-attenuated cercariae of Schistosoma mansoni exhibit high levels of resistance to challenge infection. We have previously shown that sera from these mice recognize polypeptides that are expressed on the surface of newly transformed schistosomula. We have cloned and sequenced a cDNA that encodes a 62-kDa portion of one of these polypeptides. Vaccination of mice with this 62-kDa polypeptide (designated rlrV-5) elicits high antibody titers and significant resistance to challenge infection. We report here the results of a vaccination trial in baboons with the rlrV-5 or radiation-attenuated cercariae. rlrV-5 was presented either in the form of protein micelles or complexed with the outer membrane protein of meningococcus to form proteosomes. The level of protection achieved in these groups ranged from 0 to 54%, with a mean of 27.7%. In baboons exposed to radiation-attenuated cercariae the level of protection was very high, with a mean of 84%. The resistance observed after vaccination with rlrV-5 or radiation-attenuated cercariae was reflected in the overall histopathology. Vaccination of baboons with rlrV-5 or radiation-attenuated cercariae elicited an antibody response against epitopes exposed on the surface of newly transformed schistosomula. In the case of baboons vaccinated with radiation-attenuated cercariae, this response was not limited to epitopes encompassed by rlrV-5. Analysis of individual baboon sera by ELISA demonstrated that there was a direct correlation between the anti-rlrV-5 titer and resistance to challenge worm burden, suggesting that the immunoprotective mechanism is antibody-dependent.

Animals↗
PubMed1977

Studies on the fresh water cercariae in Leyte Island, Philippines. I. Collection of snails.

During the past two years of 1975 and 1976, approximately sixteen thousand specimens of fresh water snails were examined for the presence of cercariae in Leyte Island, Philippines. These snails comprised about 14 species belonging to 7 families, and ultimately 43 species of cercariae were found, namely, 6 species from Oncomelania quadrasi, 13 species from Thiaridae, 9 species from Viviparidae and Pilidae, 8 species from Planorbidae, and 7 species from Lymnaeidae and Bulinidae. As a total, out of 15,925 snails examined, 761 or 4.78% were found infected with cercariae. Up to the present, 22 species of cercariae had been reported from the Philippines, and almost all of them are from Luzon Island only. Therefor, except for the cercaria of Schistosoma japonicum, all of the cercariae in the present study are new discoveries, and most of them are considered as new species. In this paper, the historical review on the cercarial study in the Philippines was made first, then dates and localities of snail collection in the present study were shown in details with some map and table, and general method of cercarial observation was described for the benefit of succeeding reports of this series.

Animals↗
PubMed1997

Schistosoma mattheei infection in cattle: the course of the intestinal syndrome, and an estimate of the lethal dose of cercariae.

Three groups of young oxen were infected percutaneously with cercariae of Schistosoma mattheei. Three of five oxen infected with 248 cercariae kg-1 mass died or were killed in extremis 58-70 d after infection, a fourth survived extremely severe clinical schistosomosis and the fifth was only slightly affected. None of seven calves infected with 187 cercariae kg-1 died, while one of seven exposed to 119 cercariae kg-1 was in extremis (possibly not from schistosomosis) when killed after 378 d. The LD50 appears to be in the region of the highest dose tested (248 cercariae kg-1), but depends on variations in the viability of the cercariae used. The clinical syndrome was characterized by a drastic, rapid loss in body mass; a severe diarrhoea containing blood clots; straining, gnashing of the teeth, occasional groaning, and other signs of abdominal pain; and markedly sunken eyes. Lethally infected oxen did not become recumbent until shortly before death. Some severely affected animals made remarkable, but slow, recoveries without treatment. Schistosomes, in close association with granulomata, are described-apparently for the first time-in the omental veins of cattle. Mean worm development in three calves that died or were killed in extremis in the acute stage of the disease, was 55.5%. In contrast to most previous findings with S. mattheei, in two of these animals, more female than male worms developed. The worms were recovered by perfusion and, in one animal, a large number of intestinal veins were dissected open to estimate the efficiency of the perfusion method. Only 1.9% of the total worm burden had not been removed by perfusion in this animal.

Animals↗
PubMed1998

Comparative observations on cercariae and metacercariae of Echinostoma trivolvis and Echinoparyphium sp.

Comparative observations were made on cercariae of Echinoparyphium sp. from Physa gyrina in Charlie's pond, Stokes County, North Carolina and cercariae of Echinostoma trivolvis from Helisoma trivolvis in Northampton County, Pennsylvania. The cercaria of Echinoparyphium sp. has 43 collar spines, lacks penetration and paraesophageal glands, and has a conical tail without fin folds. The cercaria of E. trivolvis has 37 collar spines, penetration and paraesophageal glands, a finger-like process at the tip of the tail and fin folds. The length of the cercarial body and tail of E. trivolvis was significantly greater than that of Echinoparyphium sp. Cercariae of both species encysted in Biomphalaria glabrata snails in single and concurrent infections. In concurrent infections with a single cercaria of each species, 2 encysted metacercariae were adjacent to each other in the saccular kidney of the snail at 24 hr postinfection. The diameter of encysted metacercariae of E. trivolvis was significantly greater than that of Echinoparyphium sp. Echinoparyphium sp. metacercariae excysted at 39 C in an alkaline trypsin-bile salts medium used previously to excyst E. trivolvis. The length of excysted metacercariae of E. trivolvis was significantly greater than that of Echinoparyphium sp.

Animals↗
PubMed1996

Microscopic observations on livers of rabbits and dogs infected with Schistosoma japonicum cercariae and early treatment with artemether or praziquantel.

UNLABELLED: To study the histopathological change of the liver of the hosts treated with artemether (Art) or praziquantel (Pra) in early stage after infection with Schistosoma japonicum cercariae. METHODS: Dogs infected once with schistosome cercariae were treated ig with Art 10 mg.kg-1 or Art capsule (ArtC) 15 mg.kg-1 on d 7, or praziquantel (Pra) 30-40 mg.kg-1 on d 21 after infection, followed by the repeated dosing once every 1 or 2 wk for 2-4 times. In rabbits, infected with 48-52 schistosome cercariae once every other day for 5 times, were treated ig with Art 10 mg.kg-1 or Pra 30 mg.kg-1 was started on d 7 or on d 21 after the first infection, followed by the repeated dosing every 1 or 2 wk for 2-3 times. RESULTS: After above mentioned dogs or rabbits were treated ig with Art, ArtC or Pra, the female worm reduction rates were 92.1%-100%. Histopathological examination showed that the reduction rates of total granuloma in the liver sections of the dogs and rabbits were 70.9%-97.3% and 76.5%-97.4%, respectively. Meantime, the structure of the hepatic lobules was normal with normal arrangement of the liver bundle. CONCLUSIONS: Early treatment with Art or Pra exhibited a promising effect of protection of the liver of the dogs and rabbits infected with schistosome cercariae. Early treatment of infection with schistosome cercariae kills the Female worms before oviposition. Thus, the host will be protected from the damage caused by schistosome eggs. Promising results were obtained when mice and rabbits received an early treatment with artemether (Art) or praziquantel (Pra). This work was to study the liver infected with cercariae and treated by intragastric gavage (ig) with Art, Art capsule (ArtC) or Pra in early stage after infection.

Animals↗
PubMed1988

Chemical signals of fish skin for the attachment response of Acanthostomum brauni cercariae.

The chemical signals of the skin surface of fish, which stimulate the attachment responses of Acanthostomum brauni cercariae, were identified by offering chemicals and fish-skin extracts in agarose substrates to the cercariae. Smaller molecules such as amino acids, fatty acids, monosaccharides, electrolytes, urea, and carbonate solutions did not stimulate attachments, but hyaluronic acid had some effects. Bovine submaxillary glycoproteins had a strong stimulating activity that disappeared after neuraminidase digestion. The stimulating components of the skin surface of fish were hydrophilic substances with molecular weights of more than 10,000. They were sensitive to neuraminidase digestion but not to hyaluronidase digestion and thus can be identified as glycoproteins. A. brauni cercariae respond only to the complete glycoprotein molecules and not to their monosaccharide components. The known attachment triggers of other cercariae are small molecules. Large glycoproteins as host signals for A. brauni cercariae may be an adaptation to muddy habitats, where various substances with low molecular weights may interfere with the host identification.

Amino Acids↗
PubMed2002

Effects of mercury and chromium upon longevity of Diplostomum sp. (Trematoda: Diplostomidae) cercariae.

Laboratory experiments were carried out to examine the impact of mercury and chromium upon survival of Diplostomum sp. cercariae. Freshly emerged cercariae were exposed to solutions of either mercury, at concentrations ranging between 0.1 and 100 microg/l, or chromium at concentrations from 2 microg/l to 2 mg/l. The mortality patterns and mean survival times (MSTs) of the exposed parasites were determined by the Kaplan-Meier estimator and were compared (log-rank test) with corresponding patterns and estimators of the unexposed controls. Mercury concentrations > or = 10 microg/l caused statistically significant changes in the mortality pattern of Diplostomum sp. cercariae and reduced MST by at least 9 h compared with the control group, in which MST was 42 h. Cercariae exposed to chromium solutions had statistically significant changes in mortality pattern only at a concentration of 2 mg/l and exhibited a reduction in MST of 8 h compared with the control (MST = 41 h). The results show for the first time that longevity of Diplostomum sp. cercariae can be reduced by direct exposure to heavy metals. Ecotoxicological effects of mercury are manifested at lower concentrations than those of chromium, and thus potentially have a higher impact on parasite populations and communities.

Animals↗
PubMed1998

Invasion of the vertebrate skin by cercariae of Trichobilharzia ocellata: penetration processes and stimulating host signals.

The penetration of Trichobilharzia ocellata cercariae into the skin of their duck hosts was described using electron microscopy and histology. The behavior patterns of the cercariae on their exposure to human skin differed only little from those known for Schistosoma mansoni cercariae. After their attachment to living human skin the cercariae crept to wrinkles within a mean of 8 s, and full penetration was achieved within a mean of 4.0 min (83 s to 13.3 min). Tail shedding occurred as early as within a mean of 6.5 s of the first penetration attempts. It was supported by a muscular sphincter at the cercarial hindbody. The skin-surface stimuli for cercarial penetration were contained in the lipid fraction of the duck and human skin surface; hydrophilic components were effective only in some T. ocellata isolates. The penetration-stimulating components of duck-skin lipids were exclusively free fatty acids with the same chemical characteristics known to stimulate penetration of Schistosoma species. Skin-surface lipids of the abnormal human host, with their higher fatty acid contents, stimulated higher cercarial penetration rates than did skin lipids of the natural duck host. Fatty acids as penetration stimuli may offer advantages for T. ocellata cercariae by increasing the specificity for an invasion of terrestrial vertebrates, which is additionally determined by cholesterol and ceramides as signals for attachment and enduring contact behavior.

Animals↗
PubMed1986

Cutaneous sensitivity induced by immunization with irradiated Schistosoma mansoni cercariae. I. Induction, elicitation, and adoptive transfer analysis of cell-mediated cutaneous sensitivity.

Exposure of C57BL/6 mice to highly irradiated (50 kR) cercariae of Schistosoma mansoni leads to the development of partial resistance against subsequent challenge with unattenuated cercariae. We have analyzed the cellular immune responses that occur during the afferent and efferent phases of this protective sensitization. Mice were immunized by exposure to irradiated S. mansoni cercariae. After challenge with irradiated cercariae, delayed-type (18-72 hr) cutaneous sensitivity reaction sites were rich in mononuclear cells and eosinophils. This reactivity was established by 4 days after sensitization, reached its maximum between 7 and 14 days after sensitization, and was maintained for over 20 weeks. These challenge reactions could be abrogated by treatment with either 200 mg/kg cyclophosphamide or 5 mg of hydrocortisone. Syngeneic adoptive transfer of cutaneous sensitivity was accomplished with lymphoid cells from the draining lymph nodes or spleens of mice sensitized 7-14 days previously. Negative selection studies of nylon-wool non-adherent cells from sensitized donors demonstrated that the cells responsible for transferring this eosinophil-rich, delayed-type cutaneous sensitivity to S. mansoni irradiated cercariae were Thy-1+, Lyt1+, Lyt2-, surface Ig- lymphocytes.

Animals↗
PubMed1986

Cutaneous sensitivity induced by immunization with irradiated Schistosoma mansoni cercariae. II. Autoimmunoregulation of cell-mediated cutaneous sensitivity and its reversal.

C57BL/6 mice sensitized by abdominal, dermal exposure to irradiated (50 kR) Schistosoma mansoni cercariae develop partial protection against subsequent exposure with unattenuated cercariae and express cell-mediated cutaneous sensitivity upon challenge with irradiated cercariae. Autoimmunoregulation occurs as a part of this sensitization, and can be demonstrated by augmentation of cutaneous sensitivity upon use of appropriate regimens of cyclophosphamide. Mice exposed to irradiated cercariae by either intraperitoneal or ear pinna routes developed a transient hyporesponsiveness to cercarial challenge. This unresponsiveness was also reversed by pretreatment with cyclophosphamide. Timed removal of the site of effective sensitization (abdominal skin) 7 days after exposure consistently led to reduced cutaneous responsiveness. This artificially induced hyporesponsiveness was reversed by either cyclophosphamide treatment or systemic administration of anti-I-Jb, but not anti-I-Jk sera. The data indicate the involvement of cyclophosphamide-sensitive, I-J-bearing T-suppressor cells or factors in the autoimmunoregulation that controls this cutaneous sensitivity. Parallel challenge infection studies in immunized mice treated with cyclophosphamide demonstrated that the resultant augmentation of cutaneous sensitivity did not lead to concomitantly elevated levels of resistance. Furthermore, successful adoptive cell transfer of cutaneous responsiveness also did not ensure protection against cercarial challenge. These observations indicate that dermal cell-mediated anti-cercarial responsiveness is not a sufficient mechanism to explain resistance in mice immunized with irradiated cercariae.

Animals↗
PubMed1985

Schistosoma mansoni: eicosanoid production by cercariae.

Cercariae of Schistosoma mansoni are stimulated to penetrate skin by certain free fatty acids. The cercariae have an active arachidonate cascade, presumably using host skin essential fatty acids as cascade precursors. Exposing cercariae to 3.3 mM linoleate for 1, 10, and 60 min resulted in production of a wide variety of eicosanoids. Using high-performance liquid chromatography, eicosanoids coeluting with prostaglandin E2, D2, and A2, leukotriene B4, and 5-hydroxyeicosatetraenoic acid standards were identified, as well as unidentified peak positions. Radioimmunoassay confirmed the presence of immunoreactive prostaglandin E1, and E2, and 5- and 15-hydroxyeicosatetraenoic acids in cercarial extracts. No eicosanoid production occurred when cercariae were exposed to 3.3 mM oleate and 1 or 330 microM linoleate. Both high-performance liquid chromatography and radioimmunoassay data indicated that cercariae regulate the production of eicosanoids through time. It is postulated that arachidonate metabolism and subsequent eicosanoid production are required for successful cercarial penetration.

Alprostadil↗
PubMed1996

Cholinergic and aminergic nervous systems in developing cercariae and metacercariae of Diplostomum pseudospathaceum Niewiadomska, 1984 (Digenea).

Comparative studies on the cholinergic (ChNS) and aminergic (ANS) nervous systems were carried out in developing cercariae and metacercariae of Diplostomum pseudospathaceum. A method for the localization of cholinesterase and nonspecific esterase activities, and the method for the histofluorescence of biogenic amines were used. The first traces of the ChNS were found in the cercarial embryo, and during growth of the cercaria, the brain ganglia and commissure, as well as anterior and posterior nerve trunks joined by commissures, were progressively developed. The fully developed ChNS was observed in the emerged cercaria. Further development in metacercariae leads to an orthogon-like structure. Histofluorescence of catecholamines appeared in the brain ganglia and the proximal part of the ventral trunks only in young cercaria (having furcae, tail stem and body of the same size). The emerged cercaria had an ANS different from the ChNS (in part of the nervous system there was no fluorescence). The differences disappeared during the development of the metacercaria. The evolutionary and functional interpretation of the various developmental rates of the ChNS and ANS were discussed.

Animals↗
PubMed1983

Lack of resistance to Schistosoma japonicum in mice immunized with irradiated S. mansoni cercariae.

Mice immunized with irradiated Schistosoma mansoni cercariae were resistant to challenge with S. mansoni cercariae (mean resistance 53%) but not to challenge with S. japonicum cercariae (mean resistance -5%). Furthermore, the antibodies induced by vaccination with irradiated S. mansoni cercariae were more reactive with S. mansoni than with S. japonicum schistosomula. These results support the concept that the resistance induced by vaccination with irradiated cercariae is immunologically specific.

Animals↗
PubMed1992

The reversible effect of glucose on the energy metabolism of Schistosoma mansoni cercariae and schistosomula.

This study on isolated cercarial bodies demonstrates that the biological transformation from cercaria to schistosomulum and the biochemical transition from an aerobic to an anaerobic energy metabolism are separate processes, which are not necessarily linked. The metabolic transition depends on the external glucose concentration and is fully reversible. In the presence of only a tracer amount of [6-14C]glucose, carbon dioxide was the major end product, but at higher glucose concentrations mainly lactate was formed. This effect could be demonstrated in cercarial bodies in water as well as in fully transformed schistosomula. In non-transformed cercariae a change towards a more anaerobic energy metabolism could be induced by an increase in the external glucose concentration, which demonstrated that the biochemical transition can occur in the absence of the biological transformation. Furthermore, the biological transformation can occur without a concomitant biochemical transition: in the presence of 5 mM glucose, lactate production by cercarial bodies during transformation was increased 50-fold, whereas in the presence of only a tracer amount of glucose the metabolic profile remained that of cercariae. Also, in fully transformed schistosomula, this transition to a more anaerobic energy metabolism was induced by increased glucose concentrations, but at low glucose concentrations carbon dioxide was the major end product, as in cercariae. The effect of external glucose on the metabolism was fully reversible. After a high glucose concentration had induced a more anaerobic metabolism in cercariae in water, the metabolism returned to an aerobic one upon removal of the glucose. Likewise, the metabolism in schistosomula switched back and forth between anaerobic and aerobic patterns, following successive changes in the glucose concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaerobiosis↗