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At least 19 recordsLinked to original sources
PubMed1990

Autoradiographic study of the attrition of migrating schistosomula in the skin of mice. II. Mice challenged with normal S. mansoni cercariae after immunization with highly irradiated cercariae.

The migratory pattern and attrition of 75Se-labelled S. mansoni challenge cercariae in CF1 mice immunized 0, 1, 3, or 5 times with 12kR- or 48kR-irradiated cercariae were investigated by compressed organ autoradiography. Mice were percutaneously inoculated with 500-1000 cercariae for each immunization and with a known count of approximately 90 cercariae at a different site for challenge. The skin, lungs, liver, other organs, and carcass were processed for autoradiography. Hepatic and mesenteric perfusions for worm collection were also sampled from day 19 through 34. In naive mice, 25% of challenge cercariae died in the skin. Skin attrition of challenge cercariae in mice immunized with 12kR-irradiated cercariae was 43% with 1 immunization, 54% with 3, and 58% with 5, whereas in mice immunized with 48kR-irradiated cercariae, skin attrition was 48% with 1, 63% with 3, and 76% with 5 immunizations. In all immunized mice, a high percentage of migrating schistosomula died in the skin within 24 hours of a challenge infection. Utilizing autoradiography, it was found that the silver foci created by single labelled worms were difficult to differentiate from those of paired worms. This study documents the induction of acquired resistance against a challenge infection in the skin by vaccination with highly irradiated cercariae, with the degree of attenuation of immunizing cercariae and the number of immunizations being closely related to the attrition rate in the skin. Finally, we discuss the contradictory views concerning the site of attrition of challenge cercariae.

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PubMed1977

Studies on the fresh water cercariae in Leyte Island, Philippines. 5. Cercariae from Planorbidae.

In the previous papers of this series, the cercariae from Oncomelania quadrasi (Part 2), from Thiaridae (Part 3), and from Viviparidae and Pilidae (Part 4) were reported continuously. The present paper deals with the cercariae from Planorbidae. These studies were all carried on during the period of 1975 and 1976 in Leyte Island, Philippines. The number of snails examined were, 2,214 Segmentina hemisphaerula, 837 Gyraulus convexiusculus, and 279 Indoplanorbis exustus. From the former two species of snails, eight species of cercariae were detected, but no cercaria was found from Indoplanorbis exustus. The eight species of cercariae comprise 3 furcocercous cercariae, 2 amphistome cercariae, one echinostome cercaria and 2 xiphidiocercariae. These are described and illustrated with a tentative name from Cercaria leyteensis no. 29 to Cercaria leyteensis no. 36, in addition with some remarks on their presumptive life histories.

Animals↗
PubMed1977

Studies on the fresh water cercariae in Leyte Island, Philippines. 4. Cercariae from Viviparidae and Pilidae.

During the period of 1975 and 1976, about two thousand snails of Viviparidae and two hundred snails of Pilidae were examined for cercarial fauna on Leyte Island, Philippines. From the snails of Viviparidae, 8 species of cercariae were found. These species consisted of two furcocercous cercariae, one monostome cercaria, three echinostome cercariae and two xiphidiocercariae. From the snails of Pilidae three species of cercariae were found; namely, one echinostome cercaria, one xiphidiocercaria, and one unknown cercaria. Among these species, one echinostome cercaria and one xiphidiocercaria were found to be common to snails of both families. In this paper these nine species of cercariae were described and illustrated with some remarks on their presumptive life cycles.

Animals↗
PubMed1978

Studies on the fresh water cercariae in Leyte Island, Philippines. 6. Cercariae from Lymnaeidae and Bulinidae.

In the previous paper of this series, the cercariae from Oncomelania quadrasi (Part 2), from the snails of Thiaridae (Part 3), from the snails of Viviparidae and Pilidae (Part 4), and from Planorbidae (Part 5) were reported continuously. In this paper the crecariae from Lymnaeidae and Bulinidae were dealt with. These studies were all carried on during the period of 1975 and 1976 in Leyte Island, Philippines. From the lymnaeid snails seven species of cercariae, comprising two echinostome cercariae, one fasciolid cercaria, and four xiphidiocercariae were detected. From the bulinid snails, only two xiphidiocercariae were found, both of which were identifiable with those from the lymnaeid snails. These seven species of cercariae are described and illustrated with a tentative name from Cercaria leyteensis no. 37 to Cercaria leyteensis no. 43, in addition with some remarks on their presumptive life histories.

Animals↗
PubMed1977

Studies on the fresh water cercariae in Leyte island, Philippines. 3. Cercariae from Thiaridae.

From 1975 to 1976, about three thousand snails of Thiaridae were examined for cercarial fauna in the northeastern part of Leyte Island, Philippines. The thiarid snails examined were Melanoides tuberculatus, Thiara (Plotiopsis) scabra, Antemelania dactylus and A. asperata, and a total of 13 species of cercariae including some important human parasites were found. These cercariae are consisted of one philophthalmid cercaria, two echinostome cercariae, three heterophyid cercariae, five xiphidiocercariae, one paragonimid cercaria and one unknown cercaria. In this paper a description of their morphology, infection rate, locality, and some remarks on the presumptive life cycle are included with illustrations and photographs.

Animals↗
PubMed1976

Immunisation of baboons against Schistosoma mansoni using irradiated S. mansoni cercariae and schistosomula and non-irradiated S. rodhaini cercariae.

In an attempt to develop a non-pathogenic procedure for immunising baboons against S. mansoni, groups of five baboons were exposed to three doses of 5000 6 Kr-irradiated S. mansoni cercariae or to similar numbers of normal S. rodhaini cercariae and challenged at week 15 with 500 normal S. mansoni cercariae. Faecal egg counts, worm and tissue egg counts, and histopathological examination, showed that neither of the immunising schedules had produced significant protection. In the second experiment baboons were injected by the intramuscular route with 31000 schistosomula of S. mansoni in three doses and the irradiation dose was reduced to near the minimum required for worm sterilisation (2-1--2-4 Kr). Challenge with 3500 normal cercariae of S. mansoni 21 weeks after the first immunising dose again showed no significant protection, although reductions of 20--30% were found in egg and worm counts resulting from the challenge. These results indicate that it may be difficult to develop an effective live vaccine for S. mansoni unless the antigenicity of the immunising larvae can be greatly increased.

Animals↗
PubMed1977

Studies on the fresh water Cercariae in Leyte Island, Philippines. 2. Cercariae from Oncomelania quadrasi.

From 1975 to 1976, more than six thousand snails of Oncomelania quadrasi were observed for cercarial fauna in the north-eastern part of Leyte Island, Philippines. Altogether, six species of cercariae including that of Schistosoma japonicum were found, namely two furcocercariae, one monostome cercaria, two xiphidiocercariae and one tail-less cercaria. In this paper a description of their morphology, infection rate, locality, and some remarks on the presumptive life cycle is included with illustrations and photographs.

Animals↗
PubMed1985

Antibody response against schistosomulum surface antigens and protective immunity following immunization with highly irradiated cercariae of Schistosoma mansoni.

The production of antibodies against the schistosomulum surface antigens of Schistosoma mansoni in response to immunization with highly irradiated cercariae was followed. Four antigens were reproducibly identified by 125I surface labelling using Iodogen and immunoprecipitation; they had mol. wts of 38, 32, 20 and 15 kD. In addition a 92 kD antigen was also evident in most experiments. It was demonstrated that the 20 kD antigen was the same as that recognized by the monoclonal antibody NIMP/M.47 and that this antigen like the 38 and 32 kD antigens was thus identified during both chronic infection and following vaccination with irradiated cercariae. Two weeks following immunization with irradiated cercariae antibody was produced only against the 15 kD antigen but at 4 weeks the major response was against the 32 kD antigen. A second immunization with irradiated cercariae boosts the antibody response so that all four antigens were strongly precipitated. Further vaccinations did not lead to the identification of further antigens. Immunization of rats with highly irradiated cercariae also resulted in antibody production against the 38, 32, 20 and 15 kD antigens. Surface labelling of schistosomula transformed from irradiated cercariae resulted in the same four antigens being precipitated as from normal cercariae indicating that irradiation did not affect transformation nor antigen expression on 3h schistosomula. Furthermore, antibodies against the same surface antigens were detectable 4 weeks after immunization with equal numbers of cercariae irradiated with 0, 5, 25 or 50 krad. Vaccination of mice with irradiated, cloned cercariae resulted in identical antibody production and similar levels of immunity directed at both an homologous or heterogeneous challenge. Thus all parasites within our laboratory population appear to express the same antigens and there was no evidence for a genetically defined variation that could account for the partial resistance to reinfection exhibited by mice vaccinated with irradiated cercariae.

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