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Interactions between two digenean parasites, Diplostomum spathaceum and Schistosoma mansoni , and their respective intermediate snail hosts, Lymnaea stagnalis and Biomphalaria glabrata , were investigated. D.spathaceum infections in juvenile L.stagnalis became patent 9 to 10 weeks post-infection and inhibited initiation of host oviposition. Adult L.stagnalis resisted infection with D.spathaceum . Both juvenile and adult B.glabrata were susceptible to S.mansoni and the infections become patent 5 weeks after infection. B.glabrata infected as juveniles failed to begin egg-laying whilst those infected as adults showed a dramatic reduction of oviposition 4 weeks post-infection, i.e before the onset of patency. Infection with D.spathaceum , but not S.mansoni , resulted in the appearance of three polypeptides (68.3, 40.8 &'38 34.5 kDa) in snail serum. The additional peptides were not directly related to failure of snail reproduction and are probably of parasite origin. Reproductive failure of infected snails was linked to the later stages of cercarial development by a method developed to manipulate infections using the anthelmintic, praziquantel. D.spathaceum and S.mansoni infections were suppressed in their snail hosts following oral treatment with praziquantel. Praziquantel was selective for cercariae and inhibited cercarial shedding of both digenean species for approximately 5 to 6 weeks before recovery. In mature B.glabrata , harbouring 7 week-old infections of S.mansoni , suppression of cercarial shedding was accompanied by temporary recovery of reproduction. Snail fecundity was halted once more 2 weeks prior to resumption of cercarial shedding. Reproductive recovery depended upon the state of infection and maturity of the host at infection. Failure of D.spathaceum to infect adult L.stagnalis was attributed to the more developed and therefore more competent internal defence system of adult snails. Infection of juvenile, immunologically immature, L.stagnalis with D.spathaceum resulted in several changes in the snail immune system and infection seemed to prevent normal development of several facets of snail immunity.

Made available in DSpace on 2014-08-20T14:31:29Z (GMT). No. of bitstreams: 1 dissertacao_isis_almeida.pdf: 2008353 bytes, checksum: d2f0dbd897b4e60effb16cb39f16d38d (MD5) Previous issue date: 2013-02-28 / Intestinal parasite infections are diseases caused by protozoa and helminth groups. They are common in developing countries and are the most frequent diseases especially among children. Although it is known that hospitalized children may be more susceptible to intestinal parasites, because they are usually neglected, few studies describe the prevalence. This study aimed to investigate the prevalence of enteric parasite infections among patients admitted to the University Hospitals Pediatric Units in the municipality of Pelotas, state of Rio Grande do Sul, Brazil, from April to December, 2012. Along with the delivery of the material for collecting feces sample, a structured questionnaire was administered to parents or guardians in order to obtain information about socioeconomic conditions of the family and how much they know about parasitic diseases. They were also given an educational material addressing the major parasitic diseases in the region. Feces samples were processed according to the techniques developed by Faust (centrifugal-flotation), Ritchie (centrifugal-sedimentation), and Baermann-Moraes. Of the 106 patients investigated, 32.1% were positive for one or more intestinal parasites. Trichuris trichiura (38.24%) and Ascaris lumbricoides (35.29%) were prevalent among helminthes. Giardia lamblia (14.7%) stood out among protozoa. Analysis of the questionnaires revealed alarming results regarding to people knowledge about parasitic diseases and the lack of parasite examination among children surveyed in this municipality. The index of parasitic diseases found in this study is a clear reflection of the lack of information behind parasitic diseases, and points to the need for implementing public policies that aim at inclusion of projects in education, including in elementary school curriculum hygiene and environmental sanitation issues, as well as fecal parasite testing in hospital routine. / Parasitoses intestinais são doenças causadas por protozoários ou helmintos, mais frequentes em países subdesenvolvidos e em desenvolvimento, acometendo principalmente as crianças. Embora se saiba que crianças hospitalizadas podem apresentar maior suscetibilidade às parasitoses intestinais, por serem geralmente negligenciadas, poucos trabalhos descrevem essa prevalência. Esse estudo teve como objetivo investigar a prevalência de enteroparasitoses em pacientes internados em unidades pediátricas de Hospitais Universitários em Pelotas, Rio Grande do Sul, Brasil, no período de abril a dezembro de 2012. Após a entrega de material para coleta de amostras de fezes, foi aplicado um questionário estruturado aos pais ou responsáveis com intuito de obter informações sobre as condições socioeconômicas da família e o conhecimento sobre parasitoses, sendo também distribuído material educativo, abordando as principais parasitoses da região. As amostras de fezes foram processadas através das técnicas de Faust (centrífugo-flutuação), Ritchie (centrífugo-sedimentação) e Baermann-Moraes. Dos 106 pacientes avaliados, 32,1% foram positivos para uma ou mais espécies de enteroparasito. Entre os helmintos, os prevalentes foram Trichuris trichiura (38,24%) e Ascaris lumbricoides (35,29%). Dentre os protozoários, destacou-se Giardia lamblia (14,7%). A análise dos questionários revelou resultados alarmantes no que diz respeito ao conhecimento da população sobre parasitoses e a ausência da realização de exames parasitológicos das crianças estudadas nesse município. O índice de parasitoses observado é um reflexo claro da falta de informação da população e atenta para a necessidade de implementação de políticas públicas que visem à inclusão de projetos na área educacional, introduzindo no currículo conteúdos que trabalhem propostas de higiene e saneamento ambiental, bem como a adoção de exames parasitológicos de fezes na rotina hospitalar.