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PubMed1990

In situ pulmonary responses of T cell and macrophage subpopulations to a challenge infection in mice vaccinated with irradiated cercariae of Schistosoma mansoni.

Cellular events related to the resistance induced by radiation-attenuated cercariae of Schistosoma mansoni were determined immunocytochemically in the lung tissues of mice. Thy-1, CD4, CD8, Mac-1 MOMA-1, MOMA-2, and Ia antigens were identified on cryostat sections by the immunogold-silver staining technique with specific monoclonal antibodies. In mice vaccinated with irradiated cercariae and challenged with normal cercariae, the number of Thy-1+ and CD4+ lymphocytes was increased dramatically relative to the normal numbers both in perivascular tissues and in focal cellular aggregates in the parenchyma of the lungs. A high ratio of CD4+/CD8+ T cells was noted in the aggregates, both in perivascular tissues and in the foci. Macrophages showing positive reactions for Mac-1, MOMA-1, MOMA-2, and Ia also infiltrated the foci. In control mice that were unvaccinated and challenged, foci showing positive reactions for the lymphocyte subpopulations barely were detectable in the lungs by day 14. The numbers of Thy-1+, CD4+, and CD8+ cells and the CD4+/CD8+ ratio in controls were considerably less than those in vaccinated/challenged mice over the period of observation. In conclusion, pulmonary cellular aggregates in vaccinated and challenged mice were composed mainly of Thy-1+ and CD4+ cell populations characteristic of delayed-type hypersensitivity (DTH) reactions. Thus, Thy-1+ and CD4+ cells in the lungs of vaccinated mice may be involved in the elimination of challenge parasites through DTH reactions.

Animals↗
PubMed1989

Ultrastructural study of the glandular system and its participation in tegument formation in Echinostoma revolutum cercaria.

Six types of gland cells occurring in the body of developing Echinostoma revolutum cercaria are described at ultrastructural level. Three types of the gland cells, lateral, ventral and dorsal, release their secretion into the tegument of cercaria during its development in the media. Another three types, paraoesophageal, penetration and proper cytogenic gland cells are preserved in the body of the free-swimming cercaria. The paraoesophageal gland cells open on the tegument surface. Secretory granules of all types of gland cells and stratification of the body tegument arising by gradual release of the contents of the above mentioned three types of gland cells are characterized in detail.

Animals↗
PubMed1989

[Further study on the immunity induced by mutagenic NTG attenuated cercariae of Schistosoma japonicum].

In order to understand the immunity induced by NTG attenuated cercariae of S. japonicum, investigations were carried out on the survival rate of mice, worm reduction rate, liver and spleen granulation etc. at different intervals between immunization and challenge (4, 6, 8, 10 and 12 wk) in mice exposed percutaneously to NTG attenuated cercariae (30 micrograms/ml NTG for 15 min). Scanning electron microscopy on tegumental surface of schistosomes from immunized mice was also performed. Results showed that better protection was achieved at a challenge time of 8 wk after initial immunizing infection as demonstrated by the higher worm reduction rate and the longer survival rate with a lower degree of liver granulation. It is suggested that acquired immunity did develop against a challenge in mice exposed to NTG-attenuated cercariae, but there were different levels of immunity at different times post-immunization. Thus week 8 appeared to be the optimal time for acquired immunity developed against a challenge infection. The possibility of induction of different levels of immunity was discussed.

Animals↗
PubMed1989

[Humoral and cellular immunity in mice immunized with mutagenic NTG-attenuated cercariae of Schistosoma japonicum].

Observation was made on humoral and cellular immunity in mice immunized with NTG-attenuated cercariae. Results showed that the specific antibody in serum of immunized mice increased gradually. The titer by ELISA and IFA were more than 1:1,280 respectively at week 7 post-immunization with NTG-attenuated cercariae (15 min. pc or 60 min. ip). SDS-PAGE electrophoresis showed that there was an extra-band of IgG with MW, between 50,000 and 40,000 in the serum of immunized mice and there was no obvious difference in IgM bands. It suggested that there were differences in not only the increase of antibody titre, but also the composition of antibody post-immunization. The results also indicated that there were differences in levels of lymphocyte proliferative response to schistosome antigens at different weeks post-immunization. The proliferative response to SEA was greater in immunized mice than in infected mice, especially in lymph node lymphocytes. It suggested that NTG-attenuated cercariae did stimulate mice to produce immunity. The dynamic characteristics of humoral and cellular immunity may play roles in the induction of protective immunity against S. japonicum.

Animals↗
PubMed1987

Intraspecific cross-protection in mice immunized with irradiated Schistosoma mansoni cercariae.

Several laboratory-maintained strains of Schistosoma mansoni were tested for their relative immunogenicity or susceptibility to anti-schistosome immunity in irradiated cercaria-immunized mice. A total of 11 strains and substrains were used; 7 were of Puerto Rican origin, 3 from Brazil, and 1 from Egypt. Mice were immunized by percutaneous exposure to 50-krad-irradiated cercariae. Immunity was assessed following challenge with cercariae of the homologous or a heterologous strain. The results showed that the choice of either the challenge or immunizing strains was not critical in the development of significant levels of protection. Extensive degrees of cross-protection developed in all intrastrain combinations tested.

Animals↗
PubMed1977

[Chaetotaxic variation of the cercariae of Schistosoma mansoni, the agent of intestinal bilharziasis, correlation with the vertebrate host of the parasite].

The chaetotaxy of the cercariae of human or simian strains of Schistosoma mansoni, a fluke producing the intestinal bilharziasis displays a characteristic difference from that of cercariae of the same parasite adapted to Mouse or wild Rat. Taking into account this differential characteristic, makes it possible to determine the human or murine origin of cercariae released from naturally infected snails during epidemiologic investigations.

Animals↗
PubMed1973

Direct filtration for recovery of Schistosoma mansoni cercariae in the field.

The recovery of schistosome cercariae from natural waters has been limited by variations in turbidity and in the accuracy of recovery with different techniques. A modification of the Rowan vacuum paper filtration method employing a battery-operated pumping system, a glass-silicone plate filter, and a specially designed filter holder is described and evaluated. Field tests on St Lucia indicate a mean filtration volume of 12.2 litres per filter at a mean turbidity of 20.3 Jackson turbidity units. Overall, 86% of the volumes filtered per filter were in excess of 6 litres. Particle size, rather than turbidity, was found to be the main factor influencing filter blockage, reading time, and accuracy. Recoveries of 0.01 cercaria (Schistosoma mansoni) per litre sampled were obtained, but the practical limit of the method is considered to be closer to 0.1 cercaria per litre sampled.

Animals↗
PubMed1973

Laboratory comparison of four cercaria recovery techniques.

The sampling of rivers and large streams for schistosome cercariae requires a method that is both highly accurate and capable of analysing several hundred litres of water regardless of turbidity. Four techniques-direct filtration by Rowan's vacuum paper filtration method, a modification of Rowan's method, continous centrifugation, and an overlay filtration method-were compared for recovery accuracy, volume of water sampled, and ease of reading under simulated field conditions. The modified Rowan technique ranked first for mean recovery accuracy (79.4%), followed by continuous centrifugation (53.8%), Rowan's technique (25.9%), and the overlay method (22.4%). With the direct filtration techniques, the filtering rate was directly related to certain turbidity factors, the maximum being 10 litres/min with the modified Rowan technique and clear water. The continuous centrifugation and overlay methods were independent of turbidity variations. Filters could be read most quickly (mean time 3.4 min/filter) with the continuous centrifugation technique because the concentrated sample made it possible to use small (47-mm) filters. Mean reading times with the other techniques (89-mm and 90-mm filters) ranged from 5.6 to 8.4 min per filter but were highly variable in relation to turbidity, particle size, and number of cercariae recovered. Direct filtration by the modified Rowan technique is considered to be the simplest and most efficient method. When flocculation is included, the resulting additional loss of cercariae (16%) is within acceptable limits.

Animals↗
PubMed1984

Identity of antigens in adult tegument, gut, egg and cercaria of Schistosoma japonicum by immunofluorescent study.

Specificity of antigens in the different stages and tissues, i.e., gut and tegument of the adult worm, cercaria and egg of Schistosoma japonicum (Sj) were examined by the direct and indirect immunofluorescent antibody method with various immune rabbit sera. Antigenic properties were completely different between gut of adult worms and egg. Cross-reactions, however, occurred among egg, tegument and stroma of adult worms. This cross-reacting antigen in tegument appeared to be unstable against formalin fixation and heating. Furthermore, the antigens in the egg were definitely shared by testes of adult male worms and also by cercaria. On the other hand, the antigenicity in cercaria against anti-adult antibodies was rather low. Cross-reactions with immune sera against the parasites other than S. japonicum were lowest in S. japonicum gut. The antigen in tegument was especially sensitive to anti-Sj adult immune sera, but distinctly less to sera from S. japonicum infections. The antigen in tegument seemed to be more specific in detecting antibodies produced by immunization than those appearing after infection.

Animals↗
PubMed1983

Mechanisms of protective immunity against Schistosoma mansoni infection in mice vaccinated with irradiated cercariae. IV. Analysis of the role of IgE antibodies and mast cells.

Mice resistant to challenge infection with Schistosoma mansoni by vaccination with highly irradiated cercariae were examined for the presence of circulating IgE antibodies and peritoneal mast cells sensitized against schistosome antigens. Significant levels of SWAP- or CAP-specific IgE antibodies could not be detected by solid phase radioimmunoassay in the sera of C57BL/6 mice during the first 6 wk after vaccination. Similarly, heatlabile antibodies capable of passively sensitizing normal mast cells for degranulation in response to SWAP could not be identified in the same sera. In contrast, peritoneal mast cells harvested from C57BL/6 mice 2 wk or later after vaccination gave strong degranulation responses when challenged with SWAP or CAP. Thus, vaccination with irradiated cercariae induces an unusual form of immediate-type hypersensitivity in which mast cells become sensitized in the absence of detectable circulating IgE antibodies. Mice deficient in mast cells (W/Wv mutant strain) were observed to develop the same resistance to challenge infection after vaccination with irradiated cercariae as nondeficient littermates. Similarly, vaccinated SJL/J mice were found to mount an extremely weak IgE response as measured by mast cell degranulation yet displayed the same level of resistance to challenge infection as other inbred mice developing potent mast cell responses. These findings argue that IgE antibodies and mast cells are not essential components in the effector mechanism of irradiated vaccine-induced immunity against schistosome infection.

Animals↗
PubMed1978

Scanning electron microscope observations on miracidium, cercaria, and cercarial papillar patterns of Schistosoma japonicum.

The surfaces of Schistosoma japonicum miracidia and cercariae were examined with the scanning electron microscope, and argentophilic papillae of S. japonicum cercariae, presumed to be sensory, with both the scanning electron microscope and the light microscope. Miracidia are covered with cilia, and the apical papilla is covered with cytoplasmic folds that form an anastomosing network. There is an excretory pore on the posterior one-third of the body. The tegument of S. japonicum cercariae is covered with spines that point in a posterior direction. The tail has a more irregular surface than the body, with fewer spines. The openings of the penetration gland ducts on a disclike area with netlike ridges at the anterior tip of the head organ are linearly arranged in 2 lateral crescents each containing 7 separate apertures. The basic number of the body papillae of S. japonicum (excluding those at the anterior end) is 56: 18 ventral, 4 acetabular, 18 dorsal, and 16 lateral (8 on each side). The number of papillae at the anterior tip is 14 (7 on each side). There are 9 papillae on the ventral side of the tail, and 10 on the dorsal and lateral sides.

Animals↗
PubMed1984

Variations of titers of immunofluorescent antibody against cercaria, adult and egg antigens developed in rabbits infected with Schistosoma japonicum before and after treatment with praziquantel.

The antibody titers of Schistosoma japonicum infected rabbits were examined against different antigens in various stages of S. japonicum using the indirect immunofluorescent antibody test with FITC-labeled anti-rabbit-gamma-globulin. The first immunofluorescent reaction could be demonstrated in the gut of adult worms 3 to 4 weeks after infection, depending on the strength of infection, then 2 weeks later within the egg shell and on the cercaria and about 1 more week later in the tegument of adult schistosomes. Treatment with praziquantel resulted in a remarkable decrease of the titers with cercaria antigen and in only a gradual decrease with egg, tegument and gut antigen. Therefore cercaria antigen seemed to be the most reliable index of successful treatment. The high sensitivity of gut and egg antigen might lead to difficulties to distinguish the successfully treated cases from chronic cases of S. japonicum infections.

Animals↗
PubMed1983

[Genetic analysis of the shedding pattern of Schistosoma mansoni cercariae by hybridization of species with early and late emission peaks].

The hybridization between Schistosomes (S. mansoni) with an early and a late shedding pattern of cercariae lead to heterozygotous cercariae whose shedding pattern is characterized by two peaks (early and late). These results demonstrate the genetic support of the shedding rhythm of cercariae and suggest the participation of the daughter sporocyst in the chronobiological phenomenon of cercarial shedding.

Animals↗
PubMed1984

Effects of physico-chemical factors on the infection of mice with Schistosoma japonicum and S. mekongi cercariae.

The three physico-chemical characteristics of water tested-pH, temperature and salinity were found to affect the infection of mice by cercariae of S. japonicum and S. mekongi. For both species of schistosomes, the range of optimal pH that showed highest infection and worm recovery rates was between 5.4-7.4 and decreased as the pH increased. Cercariae exposed to temperatures between 15 degrees-30 degrees C showed the highest infection and worm recovery rates. As temperature decreased or increased, the infection and worm recovery rates decreased. Sodium chloride concentration at low level (0.5-200 ppm) did not have great effect on the infection and worm recovery rates. The infection and worm recovery rates decreased as salinity increased. High sodium chloride concentration at 3200 ppm for S. mekongi cercariae and at 6400 ppm for S. japonicum cereariae inhibited cercarial penetration and no infection occurred.

Animals↗
PubMed1984

Early and late shedding patterns of Schistosoma mansoni cercariae: ecological significance in transmission to human and murine hosts.

A comparative analysis of the cercarial shedding of 2 Schistosoma mansoni populations originating from the same endemic area (Guadeloupe) allows us to distinguish an early (peak emergence at 1100 hr) and a late (peak at 1600 hr) shedding patterns of cercariae. This intraspecific variation in the chronobiology of S. mansoni cercariae may be related to the ecology in the transmission site. The early shedding pattern characterizes schistosome populations originated from urbanized foci where man plays the main role in the parasite transmission; the late shedding pattern characterizes schistosome populations originated from sylvatic focus where a rat (R. rattus) is the main host. The late shedding of cercariae is considered as an adaptation favoring transmission to a murine host whose behavior is preferentially crepuscular.

Animals↗
PubMed1983

Observations on cattle schistosomiasis in the Sudan, a study in comparative medicine. VI. Demonstration of resistance to Schistosoma bovis challenge after a single exposure to normal cercariae or to transplanted adult worms.

Calves were immunized with Schistosoma bovis by a single experimental exposure to 10,000 normal cercariae. Some of these calves were perfused 14 weeks later, and a part of their worm loads was surgically transplanted into groups of normal recipient calves: "WPR" group calves received 500 pairs of worms; "MR" group calves received between 650 and 1,000 male worms alone. All three groups were subsequently challenged 10 weeks after surgery with 20,000 cercariae, as were a previously unexposed group of controls ("CC"). Mean post-challenge fecal egg counts in the animals immunized with cercariae ("PC" group) rose to a maximum of only 60 eggs per gram (e.p.g.), compared to 376 e.p.g. in the CC, and maximum fecal egg counts in the WPR and MR groups were also somewhat lower than in the CC, at 152 and 250 e.p.g., respectively. In spite of the much lower fecal egg counts in the PC than in the CC group, calculated adult "challenge" worm recoveries were only reduced by 11%, but PC group tissue egg densities derived from the challenge were 78-100% lower than in the CC. The WPR and MR groups had 43% and 37%, respectively, fewer worms than the CC, and mean tissue egg densities were lower by 39-63% and 63-76%, respectively, though in most cases there were no statistically significant differences from the CC.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

[Isolation of the cercaria Diplostomum phoxini (Faust, 1918) Arvy et Buttner, 1954 (Diplostomatidae) from fresh water mollusks of the Crimea].

Data on the biology and morphology of cercariae of Diplostomum phoxini (Faust, 1918) Arvy et Buttner, 1954 are given. The cercariae were found in Radix auricularia from the middle part of the Burulcha river (Ukranian SSR, Crimea). In November, 1974 the invasion extensity of mollusks was 16.3%. No cercariae were found in spring and summer samples.

Fresh Water↗
PubMed1984

[Superficial argentophilic structures of miracidia and cercaria of Paramphistomum leydeni Nasmark 1937].

The life cycle of Paramphistomum leydeni Näsmark, 1937, is carried out in the laboratory. Adults were obtained from the rumen of a naturally infected Bos taurus in Czechoslovakia. Laboratory-reared Planorbis planorbis experimentally infected shed the first cercariae two months after exposure to miracidia. Argentophilic structures in miracidia and cercariae are described. In miracidia, these structures are similar to those previously described from species of Paramphistomum: P. togolense, P. phillerouxi, P. daubneyi, P. microbothrium. They differ, however, from those of Calicophoron calicophorum. In cercariae, argentophilic structures have some features in common with those of the species of Paramphistomum mentioned above, especially at the levels CII and AM V, but the very peculiar acetabular chaetotaxy allows us to distinguish P. leydeni from these species. Thus, each species can easily be differentiated from the related species; moreover the genus Paramphistomum as characterized by Näsmark (1937) appears to be justified.

Animals↗