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PubMedDate not supplied

[Seasonal dynamics of diurnal production and rhythmic of diurnal production of the cercaria Diplostomum volvens Nordmann, 1832 in molluscs of the genus Lymnaea from lakes of the Karasuk water system].

Infection rate of the cercariae Diplostomum volvens in molluscs of the genus Lymnaea in natural conditions (Western Siberia) was examined in 1990-1994. Experimental studies have shown that light and water temperatire are main factors regulating rhythmic of diurnal production of cercariae by molluscs.

Animals↗
PubMed1979

Histochemistry of gland cells of Eurytrema pancreaticum cercariae.

The cercariae of Eurytrema pancreaticum (Janson, 1889) possess four types of gland cells - proper cystogenic, penetration, ventral and dorsal gland cells. The secretion of ventral and dorsal gland cells is released into the tegument. The proper cystogenic gland cells are the largest and their contents serve for the formation of the cyst wall of metacercariae in the second intermediate host. The secretion of proper cystogenic gland cells contains besides neutral mucosubstances also acid mucosubstances with both carboxyl- and sulphogroups digestible with beta-glucuronidase. The secretion of penetration gland cells contains neutral mucosubstances and proteins with tyrosine, tryptophan and SS groups. The ventral gland cells contain mostly acid mucosubstances with sulphogroups, which are digested with beta-glucuronidase, and proteins with tyrosine, tryptophan and SH groups. The rudimentary dorsal gland cells contain a small amount of acid mucosubstances. The whole tegument of cercariae and the two main collecting canals of the excretory system exhibit a high alkaline phosphatase activity. The nerve ring and the main nerve truncs contain proteins with SH groups and hydrophilic lipids and exhibit a cholinesterase activity. The suckers contain a larger amount of glycogen.

Alkaline Phosphatase↗
PubMed1992

Detection of Schistosoma mansoni circulating cathodic antigen for evaluation of resistance induced by irradiated cercariae.

The appearance of serum levels of circulating cathodic antigen (CCA) detectable by a monoclonal antibody (mAb) (5H11) antigen-capture sandwich enzyme-linked immunosorbent assay (ELISA) system was evaluated during acute Schistosoma mansoni infections in female CF1 mice exposed to either 100 or 25 cercariae. Measurable CCA levels occurred in these groups at 5 and 7 wk after infection, respectively. The kinetics of appearance of CCA were thus related to the intensity of infection. The level of resistance developed by female C57BL/6 mice upon immunization with irradiated cercariae, as expressed by both worm burden and CCA levels after cercarial challenge was evaluated. Immunization conferred 44% protection against the challenge infection, and the level of CCA detected in the sera of the control group was significantly (P less than 0.02) higher than that found in the sera of the immunized group, 6 wk after challenge. These results demonstrate that CCA detection by the 5H11 mAb antigen-capture sandwich ELISA can reflect vaccine-induced resistance against S. mansoni. Localization studies showed that 5H11 reacts with a CCA epitope in the adult worm gut and to a lesser extent with the male tegument. Adaptations of this and other antigen detection systems may prove useful in monitoring the efficacy of developmental vaccines, an ability that may be essential for the extension of such studies to humans.

Acute Disease↗
PubMedDate not supplied

[Biological shedders of Opisthorchis cercariae (experimental research)].

To elaborate biological controlling measures and enhance the biological shedding [correction of bioeliminating] potential of biocenosis, 12 species of hydrobionts from 7 orders were tested for eliminating activity. The larvae of dragonflies and scale insects revealed the highest activity (eliminated from 67 to 77% cercaria). It has been established that, with the test exposition time of 3 hours, maximum elimination of cercaria takes place in the first hour of the experiment.

Animals↗
PubMed1990

Praziquantel-induced secretion of proteolytic enzyme from Schistosoma mansoni cercariae.

The effect of praziquantel (PZQ) on secretion of proteolytic enzyme by Schistosoma mansoni cercariae was examined using an azocoll assay. The cercariae secreted proteolytic enzyme in various concentrations of PZQ (0.1, 1, and 10 micrograms/ml), but secretion of enzyme was highest at the lowest concentration. PZQ-induced secretion of proteolytic enzyme was partially inhibited by treatment with verapamil and ethylene glycol-bis(beta-aminoethyl ether)N,N,N',N'-tetra-acetic acid but not by calmodulin antagonist W-7 and protein kinase C inhibitor H-7.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMedDate not supplied

[Schistosoma mansoni: quantitative aspects of the fertility and survival of worms of irradiated cercariae (3 Krad), in mice].

The effect of gamma irradiation on the fertility of female mice, as well as the survival of worms in their portal system, have been observed in four groups of outbred albino mice (Mus musculus), experimentally infected with ca 450 cercariae of Schistosoma mansoni (LE and SJ strains), by transcutaneous route. The cercariae used were a) non-irradiated (control groups), and b) irradiated with 3 Krad of gamma irradiation (Co-60). From the 33rd day on, some stability in the population of surviving worm could be observed. This population remained constant till the end of the observation period (90th day), notedly in relation to the LE strain. Thus, it was concluded that gamma irradiation (at the dose of 3 Krad) is able to hinder the worm egg production in 98.1% of the infected mice. Further, it was observed that the few detected eggs were dead. Females were found to be more resistant to irradiation. The irradiation effect on the mortality of male worms was statistically significant scarcely from the 61st day on. The long period of permanence of the sterile adult irradiated worms in the portal system of mice and their probable involvement in the development of immunoprotection (the so-called concomitant immunity, without the immunopathological involvements for the host) are here discussed.

Animals↗
PubMed1986

Identification of Schistosoma mansoni glycoproteins recognized by protective antibodies from mice immunized with irradiated cercariae.

The humoral immune responses of mice patently infected with Schistosoma mansoni and of mice vaccinated with radiation-attenuated cercariae were compared by radioimmunoassays and one- and two-dimensional polyacrylamide gel analyses of radioimmunoprecipitates. The binding observed with antibodies of mice vaccinated twice with radiation-attenuated cercariae over a period of 7 to 11 wk was less than 50% of the binding observed with antibodies of mice patently infected for 20 wk, but three to four times greater than that obtained with antibodies of mice infected for 6 wk, irrespective of whether the test antigen extracts were derived from schistosomula or adult worms. Sera of vaccinated mice precipitated a restricted number of predominantly high m.w. glycoproteins of both schistosomula and adult worms metabolically labeled with [35S] methionine. Each of the glycoproteins of 36 hr in vitro-cultured schistosomula that was precipitated by the sera of vaccinated mice was also precipitated by sera of infected mice. In contrast, sera of vaccinated mice uniquely precipitated a 38,000 m.w. glycoprotein of schistosomula cultured for 5 days and a 94,000 m.w. glycoprotein of adult male worms. Although radiation-attenuated larvae do not reach the adult stage, mice vaccinated with these still elicit a strong immune response against egg glycoproteins. In particular, an egg glycoprotein of 85,000 to 70,000 and isoelectric point of 4.8 showed an enhanced reactivity with sera of vaccinated mice in comparison with infected mice. These results show that the antibody response in mice vaccinated with radiation-attenuated larvae differs qualitatively and quantitatively from that of infected mice.

Acute Disease↗
PubMed1988

In vivo effects of monoclonal anti-L3T4 antibody on immune responsiveness of mice infected with Schistosoma mansoni. Reduction of irradiated cercariae-induced resistance.

Mice can be partially protected against challenge infections of Schistosoma mansoni cercariae by either single or multiple exposure to irradiated cercariae (x-cerc). The participation of L3T4+ lymphocytes on this resistance phenomenon was evaluated by selectively depleting this cell population through in vivo administration of mAb anti-L3T4 (hybridoma GK 1.5) at three different times in relationship to the challenge infections. Treatment with anti-L3T4 before challenge such that depletion was effective during the time of cercarial skin penetration and dermal/s.c. residence significantly reduced the level of resistance induced by x-cerc sensitization. When treatment was delayed until after challenge, depletion of L3T4+ cells coincided with either the lung or post-lung/liver phases of schistosomular migration, and normal levels of x-cerc-induced resistance were induced. In contrast to once-immunized mice, mice hyperimmunized by five exposures to x-cerc and then depleted of L3T4+ cells at the time of challenge (skin phase) still expressed resistance to the challenge. These data suggest that when mice are sensitized only once with x-cerc the challenge infection provides a necessary immunologic boost which requires L3T4+ cells for effective expression of resistance. The requirement for this anamnestic effect by the challenge infection can be circumvented by hyperimmunization. Evaluation of the immune response of one-time sensitized or hyperimmunized mice demonstrated that cellular Ag-specific proliferative responses and mitogen-induced lymphokine production were abrogated after any of the various in vivo regimens of anti-L3T4 antibody. In contrast, immunoblot analysis of humoral responsiveness revealed a correlation between the expression of resistance and the ability of sera from immunized and anti-L3T4 treated mice to recognize a 75-kDa parasite antigenic component.

Animals↗
PubMed1987

Susceptibility of Aedes aegypti and Anopheles quadrimaculatus larvae to infection with the cercariae of Plagiorchis noblei (Trematoda: Plagiorchiidae).

The impact of interspecific behavioral differences on the relative susceptibility of third instar Aedes aegypti and Anopheles quadrimaculatus larvae to infection with cercariae of Plagiorchis noblei was determined. When permitted to move freely in a column of water, larvae of Ae. aegypti were significantly more susceptible to infection with the parasite than were An. quadrimaculatus larvae. This difference is ascribed to the significantly greater activity of Ae. aegypti larvae in the water column. Since cercariae are suspended in the column, particularly near the bottom, contact with larvae of Ae. aegypti may be enhanced, whereas contact with An. quadrimaculatus larvae, which tend to remain near the surface, may be reduced. Interspecific differences other than behavior are not thought to play a major role, since immobilized larvae of the two species did not differ significantly in their susceptibility to this parasite.

Aedes↗
PubMed1987

Experimental infection of Physa heterostropha, Helisoma trivolvis, and Biomphalaria glabrata (Gastropoda) with Echinostoma revolutum (Trematoda) Cercariae.

Gross and histologic studies were done on laboratory-raised Physa heterostropha, Helisoma trivolvis, and Biomphalaria glabrata snails exposed individually to 100 cercariae of Echinostoma revolutum. Cercariae showed a predisposition for the kidneys of snails. They entered the nephridiopore, migrated up the tubular kidney, and encysted in the saccular kidney within 2 hr. Considerably more cysts were in the kidney of B. glabrata at 24 hr than in H. trivolvis or P. heterostropha kidneys. Encysted metacercariae were not infective to domestic chicks at 2 hr, but were infective by 4 hr. Biomphalaria glabrata exposed to about 1,000 cercariae/snail and necropsied either 10 or 16 wk postexposure contained 300-500 cysts/kidney; about one-half the cysts were viable and infective to chicks. Biomphalaria glabrata is an excellent second intermediate host for the laboratory propagation of E. revolutum.

Animals↗
PubMed1986

The penetration of mammalian skin by cercariae of Trichobilharzia sp. (Trematoda: Schistosomatidae) from South Africa.

The ability of the cercariae of Trichobilharzia sp., the commonest avian schistosome in South Africa, to cause dermatitis in man is confirmed, and their progress through and resultant histopathology in rodent skin are documented. These cercariae reach the subcutaneous tissue within one hour after exposure, and some migrate to the lungs. Between 46 and 97 h later, those stranded in the skin have died, while those in the epidermis are extruded by 97 h. There were haematological changes in the peripheral blood and a rapid rise and fall in the mitotic rate of the basal epithelium of the epidermis.

Animals↗
PubMed1985

Description of redia and cercaria of Paragonimus peruvianus from experimentally infected Aroapyrgus colombiensis of Condebamba Valley, Peru.

Although no natural infections with lung flukes were encountered in the hydrobioid snail Aroapyrgus colombiensis from streams in the Condebamba Valley, Peru, laboratory-bred snails were readily susceptible to infection with miracidia of Paragonimus peruvianus. The redia and cercaria are described for the first time for those of neotropical lung flukes. Cercariae inside rediae did not have a stylet and development was apparently completed outside the rediae in snail tissues. The microcercous xiphidiocercaria had 2 groups of gland cells on each side; the outer consisted of 5 cells and the inner of 3 cells, all with ducts opening at the stylet. The excretory bladder was large, often triangular, was thick-walled, and of 1 layer of cuboidal cells. The redia lacked procrusculi and had a short intestine which was slightly longer than the pharynx.

Digestive System↗
PubMed1979

Studies on encystment of Echinostoma revolutum cercariae.

Cercariae of Echinostoma revolutum encysted in the kidney of the snail Physa heterostropha within 1 hr and on mucus trails from Helisoma trivolvis, P. heterostropha and Lymnaea sp. within 2 hr. Significantly, more normal cysts were formed in mucus of Helisoma than in mucus of Physa or Lymnaea. Optimal, in vitro encystment occurred within 24 h in either Locke's 1 : 1 or Locke's 1 : 1 + 1% glucose. Significantly more normal cysts occurred in the Locke's 1 : 1 medium. Both normal and abnormal cysts from Lock's media and snail mucus excysted in an alkaline bile trypsin medium. Cercariae did not encyst in Lock'e media supplemented with casein hydrolysate or in agar cultures containing various chemicals.

Animals↗
PubMed1979

Argentophilic papillae of Schistosomatium douthitti cercariae (Trematoda: Schistosomatidae).

Argentophilic papillae of cercariae of Schistosomatium douthitti were studied by light microscopy. The basic number of body papillae was 56, excluding 20 at the anterior tip. The average number of tail papillae was 18. Average locations and spatial ranges of body papillae indicate a rather constant pattern. Tail papillae showed greater variability in location. Twenty papillae (10 on each side) at the anterior tip of cercariae were associated with gland duct openings. Two types of papillae were recognized with light microscopy--uniciliated bulbs and pits. The papilla pattern of S. douthitti differs from those of other species of schistosomes derived to date, and its constancy supports the usefulness of papillae in systematic studies.

Animals↗
PubMed1979

Dermatitis caused by cercariae of Orientobilharzia turkestanicum in the Caspian Sea area of Iran.

Cercarial dermatitis is very common among rice farmers in the Caspian Sea area of Iran. The characteristic eggs of Orientobilharzia turkestanicum were found in the feces of a plowing bull. Fifty-six percent of uninfected Lymnaea gedrosiana maintained at 24-25 degrees C produced cercariae, identical to those from natural infections, 21 days after exposure to the miracidia obtained from the feces of the bull. Cercariae of O. turkestanicum from naturally infected L. gedrosiana produced dermatitis on the arm of one of us.

Animals↗
PubMedDate not supplied

[New considerations on the role of the mouse skin surface lipids on the "in vivo" penetration of "Schistosoma mansoni" cercariae (author's transl)].

The authors have studied the effect of delipitizing and of the previously extracted skin lipids reapplication on mice experimental infected with Schistosoma mansoni cercariae. The results demonstrated that the amount of living cercariae, not penetrated, recovered after the exposition to the parasite is greater in the delipitized mice than in the other ones. The low amount of worms recovered from the treated mice might be due to the effect of the mouse skin surface lipids not only on stimulating cercarial penetration but also on allowing cercarial transformation to schistosomula during skin crossing.

Animals↗
PubMed1978

Conversion of schistosome cercariae to schistosomula in serum-supplemented media, and subsequent culture in vitro.

Both Schistosoma japonicum and S. mansoni cercariae, axenized by washing in NCTC 109, transformed to schistosomula when incubated directed in NCTC 109 containing 2--50% human or 50% rabbit serum at 37 degrees C. The resultant schistosomula were grown in vitro to adults which mated, although the females did not produce eggs. The cercaria-schistosomulum transformation took place at a slower rate in heat inactivated serum than in unheated serum.

Animals↗