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PubMed2002

Dimethicone barrier cream prevents infection of human skin by schistosome cercariae: evidence from Franz cell studies.

One approach to the prevention of schistosomiasis is the use of topical formulations to inhibit cercarial penetration of skin. A number of formulations containing either cercaricidal ingredients or components designed to inhibit penetration have been studied, but with variable results. Such studies have rarely considered the persistence of inhibitory effects through time, and to date, there have been no systematic investigations of barrier formulations. The aim of this study was to use Franz cells to investigate the effect of such barrier creams on the penetration of S. mansoni cercariae into human skin. The results show that a single application of a barrier cream based on dimethicone offers a high level of protection against penetration that is sustained for at least 48 hr.

Administration, Topical↗
PubMed2004

Mitotic responses to extracts of miracidia and cercariae of Schistosoma mansoni in the amebocyte-producing organ of the snail intermediate host Biomphalaria glabrata.

Suspensions of miracidia and cercariae of Schistosoma mansoni were subjected to repeated freeze-thaw cycles and then injected into resistant Salvador strain Biomphalaria glabrata snails. A pronounced increase in the number of mitotic figures, relative to uninjected, sham-injected, or diluent (water)-injected controls, was observed in the amebocyte-producing organ (APO) at 3 days postinjection (PI). After centrifugation of miracidia freeze-thaw extract (FTE), the resulting supernatant (FTS) and pellet possessed equal stimulatory activity that was approximately half that seen with FTE. Ultracentrifugation of miracidia FTS resulted in a supernatant that retained full activity, indicating a soluble molecule. Heat treatment of miracidia FTE reduced but did not eliminate activity, suggesting a nonprotein active component. Concentration or dilution of FTS by a factor of 10 gave a nonlinear dose-response relationship. Susceptible NIH albino snails injected with miracidia FTE had increased mitotic activity in the APO, which was much less than that seen in Salvador snails, whereas injection of miracidia FTE into Helisoma duryi had no discernable effect. Measurement of mitotic activity as a function of time PI showed no increase in numbers of mitotic figures in the APO at 18 hr but a large increase at 24 hr PI. Mitotic activity returned to preinjection levels by 96 hr PI, although a subsequent increase occurred at 120 hr PI.

Analysis of Variance↗
PubMed2005

Glucocorticosteroid hormone treatment of larval treefrogs increases infection by Alaria sp. trematode cercariae.

In many amphibian species, an apparent increase has occurred in the prevalence of limb deformities caused by parasitic trematodes. We are interested in the role of environmental stressors in increasing these infections in amphibians. One mechanism by which environmental stressors could act to increase disease prevalence is to increase circulating levels of glucocorticosteroid hormones, which are released in response to stressors and can be immunosuppressive. In the present study, we treated gray treefroZg tadpoles (Hyla versicolor) with exogenous corticosterone, which is the main glucocorticosteroid "stress" hormone in amphibians. We then exposed treated tadpoles to Alaria sp. cercariae and scored the number of mesocercariae that successfully infected the tadpoles. In addition, we assayed one function of the immune response by counting the number of circulating eosinophilic granulocytes, which are thought to be important in immune responses to macroparasites. Tadpoles treated with exogenous corticosterone developed higher parasite loads than control tadpoles did, and they had lower numbers of circulating eosinophilic granulocytes. These results provide evidence of glucocorticosteroid-mediated immunosuppression in tadpoles that may help to explain apparent increases in the numbers of trematode-induced deformities in amphibian populations during recent decades.

Animals↗
PubMed1988

An example of circular statistics in chronobiological studies: analysis of polymorphism in the emergence rhythms of Schistosoma mansoni cercariae.

Chronobiological data concerning the emergence rhythms of Schistosoma mansoni cercariae were transformed into circular variables and analysed using circular statistics. The method proposed allowed three chronobiological patterns to be distinguished for the parasite populations studied, and statistical tests for the homogeneity of samples in each group and the significant differences between groups were also carried out.

Accidents, Traffic↗
PubMed1984

Mechanisms of protective immunity against Schistosoma mansoni infection in mice vaccinated with irradiated cercariae. V. Anamnestic cellular and humoral responses following challenge infection.

Mice vaccinated with radiation-attenuated cercariae display low levels of cellular and humoral immune responses toward schistosomulum antigens, as measured in vitro by lymphocyte blastogenesis and quantitation of anti-larval antibodies by indirect immunofluorescence. Both responses wane with time after vaccination. However subsequent challenge infection provokes immune responses of classical anamnestic character, being both more rapid in appearance and of greater magnitude. Antigen responsive cells appear in lymph nodes draining the challenge site within 24 hours after infection. Both circulating anti-schistosomulum surface antibodies as well as cytophilic IgE anti-worm antigen antibodies increase substantially by 1 week after challenge. All of the anamnestic circulating antibodies belong to the IgG class. Those findings support the concept that vaccine-induced resistance to Schistosoma mansoni infection involves sensitized T and B lymphocytes, and point to the possible role of post-challenge anamnestic responses in the effector mechanism of parasite killing in this model.

Animals↗
PubMed1985

In vitro and in vivo induction of neutrophil and eosinophil chemotactic responses by Schistosoma japonicum cercaria.

High neutrophil and eosinophil chemotactic activities of soluble extract of Schistosoma japonicum cercariae (SjCe-ext) were detected in vitro by using blind-well chemotaxis chambers and Millipore filters in a dose-dependent manner. Low doses (total of 0.25 and 2.5 micrograms) of SjCe-ext induced significant neutrophilic infiltrations in normal and S. japonicum-infected (8 week) guinea pig tissues beginning at 2 hr after the intradermal injection. Eosinophilic responses were observed in the infected animals especially in early phase (2-8 hr post-injection of SjCe-ext). SjCe-ext elicited strong immediate skin reactions (at 30 min) in the infected guinea pigs. Possible roles of these chemotactic activities and hypersensitivity reaction in S. japonicum infection are discussed.

Animals↗
PubMed1986

Effects of anti-schistosomal chemotherapy on immune responses, protection and immunity. II. Concomitant immunity and immunization with irradiated cercariae.

Resistance of mice to challenge infections of Schistosoma mansoni was evaluated before and after elimination of their primary, established S. mansoni infections with the chemotherapeutic drug praziquantel. Mice treated after either 10 or 20 weeks of primary infection were challenged 6 or 10 weeks after treatment. Mice infected for for 10 weeks prior to treatment expressed progressively less resistance 6 and 10 weeks after treatment. By 10 weeks after treatment significant levels of protection were no longer observed. Resistance waned more slowly if mice were treated 20 weeks after infection, and there was still significant expression of resistance to challenge 10 weeks after treatment. A separate set of experiments evaluated the use of highly irradiated cercariae as a vaccine in mice that had been previously infected with S. mansoni and cured with praziquantel. It was observed that effective immunizations were possible in previously infected mice. These studies demonstrate that established resistance waned after treatment and the rate of loss of protection was dependent upon the duration of infection prior to treatment. Furthermore, the irradiated cercarial vaccine studies indicate that in the murine model induction of immunological resistance was feasible following chemotherapeutic treatment of infected populations.

Animals↗
PubMed1976

Schistosoma mansoni: topochemical features of intrasporocyst cercariae.

The carbohydrate rich filamentous coat investing the mature Schistosoma manosini cercaria affects important physiological and antigenic properties of the larval body surface. The origin of the filamentous coat and intrinsic topochemical properties of ccrcariae were investigated by fine structural and cytochemical examination of intrasporocyst larvae of various developmental stages. Staining results achieved with concanavalin A-peroxidase, bismuth subnitrate, silver protein, cationic colloidal iron, and polycationic ferritin indicate the presence of both neutral and acidic glycans at the external surface of the trilaminar tegumental plasmalemma, the latter saccharide moieties conferring upon this surface a superficial electronegative charge. The filamentous coat, apparent only on relatively well-developed larvae, is rich in neutral glycans, but fails to stain with cationic cytochemical reagents. Appearance of the surface coat occurs coincident with the differentiation of tegumentary cytons, the elaboration of carbohydrate-containing vesicles by Golgi complexes within these cell bodies, and the translocation of vesicles from sites of formation to the tegumental syncytium. It is likely that those saccharides, glycoproteins, and/or glycolipids present within the neutral filamentous coat, and those which constitute the acidic layer immediately superticial to the larval body surface, are intrinsic molecular constituents of the cercarial tegumental plasmalemma. Both the neutral filamentous coat and subjacent acidic layer may be regarded as distinct functional elements of the larval body surface glycocalyx. The molecular architecture of this membrane complex apparently reflects the specializations necessary for survival in fresh water followed by rapid adaptation to the serum environment of the mammalian host.

Animals↗
PubMed1975

Fine structure of possible photoreceptor in cercariae of Schistosoma mansoni.

Two structures near the anterior end of cercariae of Schistosoma mansoni are interpreted as possible photoreceptors. Each appears to be ovoid and is composed of a thin cytoplasmic wall surrounding a cavity which contains lamellae. The lamellae are extensions of modified cilia which arise from the inner wall of the cavity.

Animals↗
PubMed1975

The sensory receptors of two cercariae from Malaysia: Trichobilharzia brevis (Schistosomatidae) and Haplorchis Pumilio (Heterophyidae).

A description of sensory receptors of Trichobilharzia brevis is given. They are compared with the five Schistosomatidae described by Richard (1971), namely, Trichobilharzia ocellata, schistosoma mansoni, S. bovis, S; haematobium and S. rodhaini. All these species display very similar chaetotaxic characters. In the study of the cercaria of Haplorchis pumilio, comparison with the few Opisthorchioidea cercarial sensory organs already known has enabled the authors to characterise the chaetotaxy for this superfamily.

Animals↗
PubMed2001

Acquisition of expressed sequence tags from Schistosoma japonicum cercariae (mainland China strain) and its homology analysis.

OBJECTIVE: To understand the general profiles of the genes included in Schistosoma japonicum (Sj) cercarriae cDNA library that we have constructed for the purpose of identifying novel genes. METHODS: The phages in Sj cercariae cDNA library were transformed into plasmids after they had invaded into E.coli BM25.8, and the E.coli clones containing the plasmids were cultured in LB medium supplemented with aminobenzylpenicillin. The isolated colonies were selected for plasmid extraction and the DNAs subsequently extracted from the plasmids underwent sequence analysis with a sequencing primer to obtain the expressed sequence tags (ESTs). After sequence editing of the resulted ESTs, comparison of these sequences with those listed in the GenBank database was performed for homology analysis. The new sequences generated from the analysis were submitted to GenBank and the accession numbers acquired. RESULTS and CONCLUSION :Altogether 58 ESTs were identified among which 3 possed highly homologous nucleotide sequences with the known genes of Sj, 2 showed the homology with Schistosoma mansori genes, 7 had the homologous protein sequences, but not the nucleotide sequences, with other species, and another 27 were poorly homologous in terms of both the nucleotide and protein sequences.

Journal Article↗
PubMedDate not supplied

[Vertical distribution of trematode cercariae Cryptocotyle concavum (Heterophyidae) and Maritrema subdolum (Microphallidae) in the water column].

The effect of gravity and light on vertical distribution of Cryptocotyle concavum (Heterophyidae) and Maritrema subdolum (Microphallidae) cercariae in the water column was experimentally studied. Maximal larvae concentration was found in zones where the highest probability of contact with potential host is considered.

Adaptation, Physiological↗
PubMedDate not supplied

[Histopathology of Kingiella chilenica (bivalvia, cyamiidae) parasitized by rediae and cercariae of the Gymnophallidae family].

Gonadal and digestive gland tissues of Kingiella chilenica specimens, which were infected with trematode larvae, were examined to determine the organs that are normally invaded by these parasites. Rediae containing cercariae of this digenetic trematod, appeared exclusively restricted to the tissues of the digestive gland. Consequently, no damage or alterations were observed in the gonad or other related tissues of the infected specimens. This, linked to the fact that parasitized females may also appear with brooded embryos, supports the conclusion that the reproductive activities of the bivalve mollusc are not affected by the presence of these infecting larvae.

Animals↗
PubMed1992

Monoclonal antibody to IFN-gamma modifies pulmonary inflammatory responses and abrogates immunity to Schistosoma mansoni in mice vaccinated with attenuated cercariae.

In C57Bl/6 mice vaccinated with a single dose of attenuated cercariae of Schistosoma mansoni, the major site of immune elimination of intact challenge parasites is the lungs. The effector mechanism involves the formation of focal inflammatory responses throughout the pulmonary tissues. These foci are rich in CD4+ T cells, believed to be memory:effector cells of the Th1 type. To investigate the role of IFN-gamma in these inflammatory responses, vaccinated mice were treated with neutralizing mAb. Administration on days 4, 8, 12, and 16 post-challenge, the period over which elimination of challenge parasites takes place in the lungs, gave an average 89.5% abrogation of protective immunity. Analysis of pulmonary cell populations recovered by bronchoalveolar lavage from treated nonimmune mice at day 14 post-challenge revealed a sharp increase in pulmonary eosinophilia, relative to intact vaccinated and challenged animals. The inverse relationship between eosinophilia and protection suggests that eosinophils do not play a vital role in the immune effector mechanism in this model. Pulmonary foci of treated mice were larger, less compact, and of different cellular composition from those of control groups. They contained increased numbers of eosinophils, together with numerous multinucleated giant cells. The effects observed in the anti-IFN-gamma mAb-treated mice, together with the maintenance of MHC class II expression on alveolar macrophages in these animals, could all be explained by the production of IL-4 and other Th2 cytokines. Thus, neutralization of IFN-gamma during challenge responses may shift the Th balance towards domination by the Th2 subset.

Animals↗
PubMed1992

T cell-derived cytokines associated with pulmonary immune mechanisms in mice vaccinated with irradiated cercariae of Schistosoma mansoni.

In C57Bl/6 strain mice vaccinated with attenuated cercariae of Schistosoma mansoni, the major site of immune elimination of normal challenge parasites is the lungs. The immune effector mechanism involves formation of focal inflammatory responses; the abundance of CD4+ T cells and the activation of alveolar macrophages suggests a role for inflammatory cytokines. We report the profile of cytokines produced by cultures of leukocytes recovered by bronchoalveolar lavage (BAL) from the lungs of vaccinated and challenged mice. From 14 days after vaccination, BAL cultures contained infiltrating lymphocytes that produced abundant quantities of IFN-gamma and IL-3 on stimulation with larval Ag. Production declined from day 21 although the infiltrate of lymphocytes persisted. Challenge of vaccinated mice resulted in a second influx of IFN-gamma and IL-3-producing cells, earlier than after vaccination or in the appropriate controls. Ablation studies revealed that CD4+ T cells were essential for the production of IFN-gamma. The timing of cytokine production after vaccination, and challenge was coincident with the phases of macrophage activation previously reported. At no time could lymphocytes in BAL cultures be stimulated to proliferate with either larval Ag or mitogen, in contrast to splenocytes from the same mice. Furthermore, T cell growth factor activity was not detected in BAL cultures stimulated with Ag. We suggest that the lymphocytes recruited to the lungs are memory/effector cells. When Ag released from challenge schistosomula is presented to these cells, they respond by secreting cytokines that mediate the formation of cellular aggregates around the parasites, blocking their onward migration.

Animals↗
PubMed2005

Humoral and cellular immune responses induced in mice by purified iridoid mixture that inhibits penetration of Schistosoma mansoni cercariae upon topical treatment of mice tails.

When tested for possible blocking effect on the cercarial, serine proteinase, elastase (CE) activity, an iridoid mixture extracted from leaves of Citharexylum quadrangular abolished 31% of the enzyme activity at final concentration 15 microg. When formulated in jojoba oil and applied to mice tails followed by infection with Schistosoma mansoni cercariae, the iridoid mixture blocked cercarial penetration and caused significant reducetion (94%; P < 0.05) in worm burden in treated mice in comparison to controls. Also, immunomodulatory effects of iridoid mixture, iridoid-treated S. mansoni worm homogenate on mice were studied by measuring IgG and IgM levels against E. coli lysates (ECL), solube S. mansoni worm antigenic preparation (SWAP) and cancer bladder homogenates (CBH) as antigens by ELISA. Cellular immune responses were studied by calculating mean percent of CD4+, CD8(+)-T, B-mesenteric lymph node cells (MLNC) and CD4+, CD8(+)-T thymocytes by direct immunofluorescence staining in treated mice as compared to untreated homogenate given mice or untreated mice. Injecting mice with serial dilutions of iridoid mixture resulted in fluctuation, peaks and troughs, in both IgG and IgM responses against the above mentioned antigens. 1st and 2nd immunizations with iridoid mixture treated homogenate resulted in significantly elevated (P < 0.05). IgM and IgG levels against the 3 used antigens in comparison with sera from control mice. Immunized mice with homogenate treated with iridoid mixture showed a significant increase (P < 0.05) in CD4+T thymocytes, a non significant increase in CD8+T thymocytes, a significant increase (P < 0.05) in CD4+T lymphocytes (MLNC) and a non significant increase in CD8+ T- and B-lymphocytes (MLNC) compared with mice immunized with untreated homogenate or non-injected normal mice.

Administration, Topical↗
PubMed2001

[The case of dermatitis in the human as a result of the influence of the cercaria of the bird schistosome].

There are numerous cases of dermatitis described world-wide and resulting from the influence of the furcocercaria of the bird schistosome. The host snail species of the schistosome, producing thousands of furcocercaria are common in our country. But, because of too general symptoms of dermatitis resulting from the influence of the schistosome of the larvae, there are many unrecognisable cases. The reaction described was typical of a twenty-seven-year-old man collecting snails in the Piechota Bay in Gostynin (the Province of Kuyavia and Pomerania). In that reservoir, individuals of Lymnaea stagnalis were found, which were infected with sporocysts and furcocercaria of Trichobilharzia ocellata. In the laboratory conditions, a high expulsion of cercaria was observed, which amounted to over 8000 larvae per snail.

Adult↗