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PubMed2006

Infection patterns in white sea blue mussels Mytilus edulis of different age and size with metacercariae of Himasthla elongata (Echinostomatidae) and Cercaria parvicaudata (Renicolidae).

Infection of mussels Mytilus edulis L. by 2 trematode species was studied in a natural intertidal population in the Chupa inlet of the White Sea. The prevalence of metacercariae of Himasthla elongata (Mehlis, 1831) and Cercaria parvicaudata (Stunkard & Shaw, 1931) in mussels reached 100% in 3 to 4 yr old molluscs and remained at this level in older individuals. Infection intensity increased evenly with the age of the molluscan host, showing a tendency to decrease only in the oldest (9 yr old) mussels. These patterns of age dynamics of prevalence and infection intensity were associated with accumulation of trematode larvae in the course of the molluscs' lives. Ability of metacercariae to exist in mussels for long periods (at least 2.5 yr) was verified in the course of an experiment, during which infected molluscs were kept in a subtidal net cage. Decrease of infection intensity in the oldest individuals may reflect selective mortality of the most severely infected molluscs. Among mussels of the same age, higher infection intensity values occurred in larger individuals. This may be due to an enhanced pumping rate in large molluscs, which increases the probability of cercariae, free-living trematode larvae, infecting them via water currents.

Analysis of Variance↗
PubMed1978

Quantitative collection and proteolytic activity of preacetabular gland enzyme (s) of cercariae of schistosoma mansoni.

Protease-containing preacetabular gland secretion can be collected from cercariae of Schistosoma mansoni by stimulation with penetration-inducing skin surface lipid, but the method lacks quantitative control because of variability of the lipid. Two commercially available free fatty acid fractions of skin lipid active in stimulating cercariae to penetrate skin, linolenic and linoleic acids, were substituted for skin surface lipid in a technique which provides an improved method of secretion collection. The pattern of protease activity of secreted enzyme (s) was followed throughout patency of infection of a group of snails with the same date of exposure. Day-to-day variability was a characteristic feature of all parameters studied. Major trends were elevated enzyme activity and cercarial emergence during midpatency.

Animals↗
PubMed1982

Regional and splenic lymphocyte proliferative responses of mice exposed to normal or irradiated Schistosoma mansoni cercariae.

Developing larvae of Schistosoma mansoni migrate through various tissues en route to the liver and mesenteric veins of their definitive host. Regional (lymph node) and systemic (spleen) blastogenic responses to cercarial, adult and egg antigens were measured in CBA/J mice at various times after exposure to normal or irradiated S. mansoni cercariae. Among the separate lymph node groups studied were those draining the tail, thoracic region, intestines, head and neck, and the pelvis. Blastogenic responses were assayed by a micromethod requiring 10(5) cells in 20 microliter volumes per culture. Up to 5 weeks post-cercarial exposure the pattern of responses in lymphoid tissues of infected mice coincided with the migratory route of the parasites. Following oviposition, cellular reactivity was pronounced in all lymph node groups. The reactivity of mice exposed to irradiated cercariae followed a pattern suggestive of a sustained antigenic stimulus only in the nodes draining the tail and lungs. Splenic (systemic) reactivity was roughly comparable between the two exposure groups. These data show the independence and vast differences in the host regional responses following normal or irradiated cercarial exposure.

Animals↗
PubMed1984

Comparison of Schistosoma mansoni migration patterns in normal and irradiated cercaria-immunized mice by means of autoradiographic analysis. Evidence that worm elimination occurs after the skin phase in immunized mice.

Migration and elimination of radiolabeled Schistosoma mansoni were compared in naive and irradiated cercaria-immunized mice by autoradiography of compressed host tissues. The results indicated that 1) most of the normal elimination of schistosomula in unimmunized mice and the additional elimination in immunized mice occur at some point(s) after arrival of schistosomula in the lungs and before their development into adult worms, 2) migration of schistosomula from skin to lungs is delayed for several days but not reduced in immunized mice, 3) migration of schistosomula from lungs to liver is delayed for several days in immunized mice, and 4) schistosomula reach the liver in reduced numbers or are killed and cleared in the liver in greater numbers in immunized mice. The lung chop procedure was shown to recover schistosomula from control and irradiated cercaria-immunized mice with equal efficiency. Autoradiography of all tissues of the body demonstrated that, in both control and immunized mice, at least 20-25% of the schistosomula detectable 2 and 3 weeks after infection were present in tissues other than the skin, lungs and liver.

Animals↗
PubMed1992

The role of IgG antibodies from irradiated cercaria-immunized rabbits in the passive transfer of immunity to Schistosoma mansoni-infected mice.

Antibodies of the IgG subclass isolated from the sera of rabbits immunized with cercariae subjected to 50 kilorads of gamma irradiation passively provided partial immunity against Schistosoma mansoni challenge in C57B1/6J mice. These mice exhibited reductions in adult worm burdens of 43-61% compared with recipients of normal rabbit antibodies. Passively transferred IgG antibodies were most effective when given 4-7-days postchallenge; they were less effective when given just before challenge, and were totally ineffective when given 15 days postchallenge. It was also shown that the Fc portion of the IgG molecule was important for passive transfer of immunity. Finally, we observed that although some antibodies from irradiated cercaria-immunized rabbits recognized keyhole limpet hemocyanin (KLH), these KLH cross-reacting antibodies were not necessary for successful passive transfer of immunity. Antibodies from a KLH-immunized rabbit also failed to passively protect mice.

Animals↗
PubMed1996

Protection against Schistosoma mansoni and associated immune responses induced in the vervet monkey Cercopithecus aethiops by the irradiated cercaria vaccine.

The efficacy of the radiation-attenuated schistosome vaccine in eliciting protective immunity was investigated in the vervet Cercopithecus aethiops. Three groups of test animals received one, three, or five exposures to 5,000-9,000 cercariae attenuated with 30 krad of gamma radiation from a 137Cs source, while a fourth group served as challenge controls. After a single vaccination, no statistically significant protection was found; after three vaccinations it reached its highest peak (48%) and five exposures resulted in reduced protection (39%). Examination of immunologic parameters supported these findings, with proliferative responses of peripheral blood lymphocytes being greatest in the group vaccinated three times. Specific immunoglobulin G (IgG) levels also peaked after three vaccinations, with clear evidence of a reduction after the fourth and fifth exposures. There was a clear correlation (r = 0.66) between the antibody level at the time of challenge and the protection observed in individual vervets. These data demonstrate that protective immunity to Schistosoma mansoni can be achieved with the attenuated vaccine in a highly susceptible nonhuman primate (i.e., 82% maturation of penetrant cercariae was recorded in challenge control animals in this study). However, they also indicate that there is a ceiling to this protection. Furthermore, increasing the number of vaccinations beyond a certain point, instead of boosting protection may cause it to diminish, possibly due to the induction of immunoregulatory mechanisms.

Animals↗
PubMed1996

A simple computer-assisted method to identify schistosome cercariae.

Several methods have been suggested to identify schistosome cercariae. In the present work, a new method is proposed, based on the analysis of the distribution of sensory endings (sensillae) on the body of the cercariae, revealed by an impregnation with silver nitrate. We determined the mutual distances between the sensillae and calculated the mean values, standard deviations, coefficients of asymmetry, and of kurtosis of the distribution of these mutual distances. Applied to two species, Schistosoma mansoni from Brazil and S. intercalatum from Cameroon, these mutual distances had the same mean value and the same standard deviation but quite different coefficients of symmetry (0.34 +/- 0.11 versus 0.73 +/- 0.08; P < 0.0001) and of kurtosis (-0.82 +/- 0.27 versus -0.58 +/- 0.31; P < 0.0001). The latter two indices were therefore very effective for discriminating the two species. The present method can be applied to other species and to hybrids in the field.

Animals↗
PubMed1998

Preventive effect of artemether in rabbits infected with Schistosoma japonicum cercariae.

AIM: To study the effect of artemether (Art) for prevention of schistosomal infection. METHODS: Rabbits with single infection or reinfection with Schistosoma japonicum cercariae were treated intramuscularly (i.m.) or intragastrically (i.g.) with Art 5 -20 mg.kg-1 on d 7-15 after the first infection, followed by various regimens. RESULTS: When rabbits were injected i.m. Art 7.5 mg.kg-1 (i.e., one half of the effective dose given i.g. on d 7) followed by once every week for twice, the female worm reduction rate was only 42%. In infected rabbits treated i.g. with Art 10-20 mg.kg-1 given in the same administration schedule, the female worm reduction rates were > 91%. When Art 15 mg.kg-1 was given to rabbits on d 7-14 and the following dose of the drug was given at intervals of 7-14 d, the female worm reduction rates were > 94%. In rabbits reinfected with cercariae, the female reduction rate of Art given i.g. once a week for 3 times since d 8 after the first infection was 96% which was similar to that given once a week twice since d 14 after the first infection. CONCLUSION: Art should be given i.g. on d 7-15 after infection, followed by repeated dosing once every 7-15 d for a total of 3 doses. Art given i.g. daily for 2 consecutive days or given at 1-wk intervals since 7-15 d after infection also showed preventive effect.

Animals↗
PubMed1975

Appearance of Fasciola cercariae in rice fields determined by a metacercaria-detecting buoy.

The appearance of Fasciola cercariae in aquatic rice fields of fluky areas was investigated by using a metacercaria-detecting buoy. The buoy consisted mainly of a foam styrol disk 10 cm in diameter and 3 cm in thickness, and a polyethylene sheet 16 cm in diameter covering the bottom and side of the disk. Each buoy was floated at each corner of a section of rice fields. To determine the serial appearance of Fasciola cercariae, the polyethylene sheet was renewed at intervals of a week over a period of rice cultivation and the number of metacercariae was counted on each sheet. In most rice fields an evident peak of metacercarial detection was observed between the middle of July and the end of August. The time of the first detection of cysts in a small number varied from one section to another of the same field or from one area to another. Metacercariae decreased in number in accordance with drying up the fields. The metacercaria-detecting buoy method was applied to rice fields fertilized with cattle manure for 7 days in mid-summer, as well as to fields located closely to cattle pens, but not fertilized. Many cysts were detected from both groups of fields. The results obtained from weekly observation on the population of snails, particularly infected snails in their habitats, and those from the cercarial appearance detected by means of the buoy method were essentially the same.

Animals↗
PubMedDate not supplied

[Cercaria splendens Szidat--larva of the trematode Azygia lucii Looss].

The belonging of the only one "gigantic cercaria", Cercaria splendens, to the species Azygia lucii was proved experimentally. The geographic distribution of A. lucii is considerably wider than it has been indicated up to now. The distribution area of A. robusta is also confined not only to the Asiatic part of the USSR. The following characters are suggested for distinguishing the Azygia species: the shape and size of the pharynx, the spread of vitellaria beyond the posterior border of the testes and ratio between the sizes of suckers.

Animals↗
PubMedDate not supplied

[Vertical migration of cercariae of the littoral trematode Renicola thaidus (Trematoda: Renicolidae) in the water layer].

Vertical dispersion of the cercariae Renicola thaidus in the water layer was examined in experiments. Dispersion of larvae of 1 and 6 hours old were investigated in different conditions of illumination. It was found out that in the first hour of life the larvae both in light and dark conditions display a negative geotaxis. 6 hours later, the reaction alternates. Both in light and dark condition, the larvae show a positive geotaxis. This changes of vertical dispersion is the result of inversion of the reaction onto the gravitation, that depends on biology of cercariae examined.

Animals↗
PubMedDate not supplied

[Cercaria splendens Szidat - the larva of the Trematode Azygia lucii Looss].

The belonging of the only one "gigantic cercaria", Cercaria splendens, to the species Azygia lucii was proved experimentally. The geographic distribution of A. lucii is considerably wider than it has been indicated up to now. The distribution area of A. robusta is also confined not only to the Asiatic part of the USSR. The following characters are suggested for distinguishing the Azygia species: the shape and size of the pharynx, the spread of vitellaria beyond the posterior border of the testes and ratio between the size of suckers.

Animals↗
PubMed2000

[Immunoscreening of Schistosoma japonicum adult worm cDNA library by sera from rabbits vaccinated with ultraviolet-attenuated cercariae].

OBJECTIVE: To find out the major antigenic molecules of radiation-attenuated cercariae, and provide some useful candidate antigens for developing schistosomiasis vaccine. METHODS: Schistosoma japonicum (Sj) adult worm cDNA library was screened by sera of rabbits vaccinated with ultraviolet-attenuated cercariae, and the inserts of positive clones were specifically amplified by PCR and sequenced. RESULTS: Ten positive clones were obtained after three rounds of screening, and the size of Sj cDNA fragments of the positive clones ranged from 1.5 kb to 1.8 kb. Five partial sequences were got after preliminary sequencing. Two of them had significantly homology with Sj dynein light chain 5(DLC 5) gene and Sj mitochondrial gene, respectively, and the others were identified as partial sequences of novel genes for they showed only partial homology with non-schistosome genes or other organism in the database. CONCLUSIONS: The positive clones may be the genes encoding the antigens that can elicit protective immunity against Sj.

Animals↗
PubMedDate not supplied

[Gladular formations in cercariae and the main trends in their evolution].

Hystological studies of glandular formations in 16 species of cercariae were carried out. Their secretion was found to contain acid and neutral mucopolysaccharides, mucins, mucoproteins and elastin. The classification of types of glands is specified. The glands can be of the following types: cystognic case forming, mucoid and glands of penetration. The glands performing uncertain functions and caudal ones are separated into a special group. On the basis of obtained data on the uniformity of chemical compounds of the secretion of glands belonging to different groups their common origin has been suggested. It has been shown that the main trends of the evolution of glandular formations in cercariae depends on the evolution of the life cycle of trematodes.

Animals↗
PubMed1992

Identification of Schistosoma mansoni, S. rodhaini, S. bovis, S. haematobium, and S. intercalatum cercariae using segmentation analysis.

Cercariae of five species of schistosomes identified with certainty were fixed in boiled alcohol and mounted in glycerol-alcohol mixture. The cercarian body (Cbl) and tail-furcae lengths (Ctl) were measured, the values of which were treated using a computer. Even mean values allowed partly identification of the present species, the segmentation analysis gave better informations for separating any cercaria taken at random, with a given probability (p). Thus, five classes (A, B, C, D, E) have been established: class A: Cbl > 139 microns and Ctl, > 236 microns, p = 0.59 to be considered as S. bovis; class B: Cbl > 139 and Ctl < 236, p = 0.86 to be considered as S. haematobium; class C; Cbl < 114 microns, p = 0.75 to be considered as S. intercalatum; class D: 114 < Cbl < 125 microns, p = 0.57 to be considered as S. mansoni; class E: 125 < Cbl < 139 microns, p = 0.57 to be considered as S. rodhaini. Two groups of schistosome have been established on basis of cercarian morphometry with S. intercalatum, S. mansoni and S. rodhaini from one side, S. haematobium and S. bovis to the other side.

Animals↗
PubMed2003

The effects of myrrh (Commiphora molmol) on the infected snails of Schistosoma sp. and their egg masses: effect on shedding of cercariae and on snail fecundity.

Myrrh has molluscicidal effect on infected Bulinus truncatus and Biomphalaria alexandrina snails at low concentrations (10 & 20 ppm respectively) after 24 hours exposure. The number of dead-snails increased with prolongation of exposure time. All Schistosoma free cercariae were killed by 2.5 ppm within 15 minutes. One day-old egg masses were more susceptible to the ovicidal effect of Myrrh than the five-day old ones. Both types of eggs were more resistant to the effect of Myrrh than the adult snails, embryogenesis began to stop at 20 ppm and eggs were all killed at 60 & 80 ppm. Shedding of cercariae of Schistosoma mansoni from infected B. alexandrina stopped at 1 ppm and was suppressed at 0.8 ppm. Snail fecundity decreased at 1 ppm.

Animals↗
PubMed2003

[Immunoscreening of Schistosoma japonicum adult worm cDNA library with sera vaccinated with cercaria antigen and analysis of novel genes].

OBJECTIVE: To explore antigens possessing common immunogenicity with Schistosoma japonicum (Sj) cercariae antigens, and to find out new candidate antigens for schistosomiasis diagnosis and vaccine. METHODS: Sj adult cDNA library was screened using sera from rabbits vaccinated with Sj cercariae antigen, the inserts of positive clones were amplified by PCR, all positive clones were sequenced and the data were analysed using Nucleotide BLAST software of NCBI and Expert Protein Analysis System of Swiss Institute of Bioinformatics. RESULTS: Thirteen positive clones were obtained after three rounds of immunoscreening, and all amplified by PCR. Among four novel genes, SjCAI, SjCA, SjCAI-2 and SjCAI-3 (GenBank accession number: AF495883, AF515834, AY118086 and AY129303, respectively) encoded proteins with 353, 161, 137 and 72 animo acids respectively. Sj CAI protein contained six DNA-binding zinc fingers and showed some homology to gastrula zinc finger protein XLCGF48.2; proteins encoded by SjCA, SjCAI-2 and SjCAI-3 respectively contained N-glycosylation sites and phosphorylation sites. CONCLUSION: Novel genes were obtained by immunoscreening Sj adult cDNA library.

Amino Acid Sequence↗