Pathological effects of ECHINOSTOMA PARAENSEI infection associated with pyogenic abscesses caused by PSEUDOMONAS AERUGINOSA in swiss mice / Efectos patológicos de la infección por ECHINOSTOMA PARAENSEI asociada a abscesos piógenos causados ​​por PSEUDOMONAS AERUGINOSA en ratones suizos / Efeitos patológicos da infecção por ECHINOSTOMA PARAENSEI associada a abscessos piogênicos causados ​​por PSEUDOMONAS AERUGINOSA em camundongos suíços

The trematode Echinostoma paraensei is an intestinal parasite transmitted by ingestion of the infectious stage of metacercariae. For scientific purposes, its life cycle has been maintained in the laboratory, allowing analysis using various biological approaches. Different parasite isolates have revealed atypical patterns of migration and establishment in ectopic sites in Swiss-Webster mice. During the investigation of the biological life cycle of an E. paraensei isolate from the silvatic rodent Nectomys squamipes collected in the municipality of Rio Bonito (State of Rio de Janeiro), a bacterial coinfection with Pseudomonas aeruginosa was observed, which produced anatomopathological alterations, mainly in the liver, bile ducts, pancreas, and small intestine. The main macroscopic signs were the whitish suppurative pyogenic punctual lesions. The histological sections stained by hematoxylin-eosin showed an intense inflammatory reaction formed by mononuclear cells and macrophages surrounding the bile ducts, although the hepatic parenchyma still presented its normal aspect. Thus, pyogenic abscesses can be associated with E. paraensei infection depending on the strain and aggravating pathogenesis in the definitive host.

El trematodo Echinostoma paraensei es un parásito intestinal transmitido por ingestión de la etapa infecciosa de las metacercarias. Para fines científicos, su ciclo de vida se ha mantenido en el laboratorio, lo que permite el análisis mediante diversos enfoques biológicos. Diferentes aislamientos de parásitos han revelado patrones atípicos de migración y establecimiento en sitios ectópicos en ratones Swiss-Webster. Durante la investigación del ciclo biológico de un aislado de E. paraensei del roedor silvático Nectomys squamipes colectado en el municipio de Rio Bonito (Estado de Rio de Janeiro), se observó una coinfección bacteriana con Pseudomonas aeruginosa, que produjo alteraciones anatomopatológicas, principalmente en el hígado, los conductos biliares, el páncreas y el intestino delgado. Los principales signos macroscópicos fueron las lesiones puntuales piógenas blanquecinas supurativas. Los cortes histológicos teñidos con hematoxilina-eosina mostraron una intensa reacción inflamatoria formada por células mononucleares y macrófagos que rodeaban las vías biliares, aunque el parénquima hepático aún presentaba su aspecto normal. Por tanto, los abscesos piógenos pueden asociarse con la infección por E. paraensei dependiendo de la cepa y agravando la patogenia en el hospedador definitivo.

O trematódeo Echinostoma paraensei é um parasita intestinal transmitido pela ingestão da fase infecciosa das metacercárias. Para fins científicos, seu ciclo de vida foi mantido em laboratório, permitindo análises por meio de diversas abordagens biológicas. Diferentes isolados de parasitas revelaram padrões atípicos de migração e estabelecimento em sítios ectópicos em camundongos Swiss-Webster. Durante a investigação do ciclo de vida biológico de um isolado de E. paraensei do roedor silvático Nectomys squamipes coletado no município de Rio Bonito (Estado do Rio de Janeiro), foi observada uma coinfecção bacteriana por Pseudomonas aeruginosa, que produziu alterações anatomopatológicas, principalmente no fígado, dutos biliares, pâncreas e intestino delgado. Os principais sinais macroscópicos foram as lesões pontuais piogênicas supurativas esbranquiçadas. Os cortes histológicos corados pela hematoxilina-eosina mostraram intensa reação inflamatória formada por células mononucleares e macrófagos circundando as vias biliares, embora o parênquima hepático ainda apresentasse seu aspecto normal. Assim, abscessos piogênicos podem estar associados à infecção por E. paraensei dependendo da cepa e agravando a patogênese no hospedeiro definitivo.

Angiostrongylus minasensis n. sp.: new species found parasitizing coatis (Nasua nasua) in an urban protected area in Brazil / Angiostrongylus minasensis n. sp.: nova espécie encontrada parasitando quatis (Nasua nasua) em área de proteção urbana no Brasil

Abstract Currently, there are 21 species of Angiostrongylus that parasitize the pulmonary or mesenteric arteries of wild and domestic rodents, felids, canids and human. Species of Angiostrongylus have cosmopolitan distribution covering tropical, subtropical and temperate regions. The procyonid Nasua nasua (coati) is a reservoir host for a wide variety of parasites that may be harmful to its populations or may contain etiological agents with zoonotic potential. In urban areas, coatis are usually found in close association with humans and domestic animals. We morphologically and molecularly characterized a new species of Angiostrongylus found in N. nasua in a protected area within Belo Horizonte, Brazil. The new species of Angiostrongylus differs from other species of the same genus in terms of the length and bifurcation level of the lateral and ventral rays, the length of spicules and female tail morphology. Molecular phylogenetic results based on the mitochondrial cytochrome c oxidase subunit 1 gene suggest that the newly identified species belongs to a genetic lineage that is separate from other species of Angiostrongylus. This new species was collected from the mesenteric arteries of N. nasua. It was named Angiostrongylus minasensis n. sp..

Resumo Existem 21 espécies de Angiostrongylus que parasitam as artérias pulmonares ou mesentéricas de roedores silvestres e domésticos, felídeos, canídeos e homem. Espécies de Angiostrongylus têm uma distribuição cosmopolita que abrange regiões tropicais, subtropicais e temperadas. O procionídeo Nasua nasua (quati) é hospedeiro de vários parasitos que podem ser prejudiciais para suas populações ou conter agentes etiológicos com potencial zoonótico. Nas áreas urbanas, os quatis podem ser encontrados em estreita associação com seres humanos e animais domésticos. Nós caracterizamos morfológica e molecularmente uma nova espécie de Angiostrongylus encontrada em N. nasua de uma área protegida na cidade de Belo Horizonte, Brasil. A nova espécie de Angiostrongylus difere de outras espécies do mesmo gênero pelo comprimento e nível de bifurcação dos raios lateral e ventral, o comprimento dos espículos e a morfologia da cauda da fêmea. Resultados moleculares e filogenéticos baseados no gene mitocondrial citocromo c oxidase subunidade 1 indicam que a espécie recém-identificada pertence a uma linhagem genética separada de outras espécies de Angiostrongylus. O presente relato descreve uma nova espécie de Angistrongylus coletada das artérias mesentéricas de N. nasua, denominada Angiostrongylus minasensis n. sp..

Helminth metacommunity structure of wild rodents in a preserved area of the Atlantic Forest, Southeast Brazil / Estrutura da metacomunidade de helmintos de roedores silvestres em uma área preservada da Floresta Atlântica, sudeste do Brasil

Abstract The helminth fauna and metacommunity structure of eight sympatric sigmodontine rodents were investigated at the Serra dos Órgãos National Park, an Atlantic Forest reserve located in the State of Rio de Janeiro, southeast Brazil. Rodents of the species Abrawayaomys ruschii, Akodon montensis, Blarinomys breviceps , Delomys dorsalis, Oligoryzomys flavescens, Oligoryzomys nigripes, Oxymycterus quaestor and Thaptomys nigrita were found infected with helminths. Akodon montensis presented the highest total helminth species richness, with six different species of helminths. The nematode Stilestrongylus lanfrediae was the most abundant and prevalent helminth species observed. The host-parasite network analysis showed little interactions among host species. Akodon montensis seems to act as a keystone-species in the rodent community. This species shared the nematodes Stilestrongylus aculeata with A. ruschii and Protospirura numidica criceticola with T. nigrita, and the cestode Rodentolepis akodontis with D. dorsalis. The congeners host species O. flavescens and O. nigripes shared the nematodes Guerrerostrongylus zetta and S. lanfrediae. The rodents B. breviceps and O. quaestor did not share any helminths with other hosts. The helminth metacommunity showed a random pattern on both infracommunity and component community levels, indicating different responses by each helminth species to the environmental gradient.

Resumo Foram investigadas a helmintofauna e suas estruturas da metacomunidade em oito roedores sigmodontíneos simpátricos ao longo do Parque Nacional da Serra dos Órgãos, uma reserva de Mata Atlântica no estado do Rio de Janeiro, Brasil. Roedores das espécies Abrawayaomys ruschii, Akodon montensis, Blarinomys breviceps, Delomys dorsalis, Oligoryzomys flavescens, Oligoryzomys nigripes, Oxymycterus quaestor e Thaptomys nigrita foram infectados por helmintos. Akodon montensis apresentou a maior riqueza total de espécies de helmintos, com seis espécies. O nematoide Stilestrongylus lanfrediae foi a espécie de helminto com maior abundância e prevalência. A análise de rede parasito-hospedeiro mostrou poucas interações entre as espécies hospedeiras e A. montensis atuou como uma espécie-chave na comunidade de roedores. Esta espécie compartilhou os nematoides Stilestrongylus aculeata com A. ruschii e Protospirura numidica criceticola com T. nigrita, e o cestoide Rodentolepis akodontis com D. dorsalis. As espécies congêneres O. flavescens e O. nigripes compartilharam os nematoides Guerrerostrongylus zetta e S. lanfrediae. Os roedores B. breviceps e O. quaestor não compartilharam helmintos com outros hospedeiros. A metacomunidade de helmintos mostrou um padrão aleatório em ambos os níveis, comunidade componente e infracomunidade, indicando diferentes respostas de cada espécie de helminto ao gradiente ambiental.

Morphological effects on helminth parasites caused by herbicide under experimental conditions / Efeitos morfológicos em helminto parasito causado por herbicida em condições experimentais

Abstract Helminth parasites have been studied as potential accumulators for different pollutants. Echinostoma paraensei is a foodborne trematode whose vertebrate host, the rodent Nectomys squamipes, is naturally exposed to environmental pesticides. However, little information exists regarding the pesticide's effects on helminths. This study investigated the morphological effects on the trematode, E. paraensei, after experimental Roundup® herbicide exposure, in concentrations below those recommended for agricultural use. After two hours of exposure, scanning electron microscopy (SEM) showed changes to the tegument, such as furrowing, shrinkage, peeling, spines loss on the peristomic collar, and histopathological evidence of altered cells in the cecum and acinus vitelline glands with vacuoles and structural changes to the muscular layers. Glycidic content was decreased, primarily in the connective tissue. As E. paraensei is an intestinal parasite of the semi-aquatic wild rodent, N. squamipes, it is predisposed to pesticide exposure resulting from agricultural practices. Therefore, we emphasize the need to evaluate its impact on helminth parasites, due to their pivotal role in regulating host populations.

Resumo Helmintos parasitos tem sido estudados como acumuladores potenciais para diferentes poluentes. O trematódeo E. paraensei tem como hospedeiro vertebrado o roedor Nectomys squamipes naturalmente exposto a pesticidas no meio ambiente. No entanto, pouca informação está disponível sobre os efeitos dos pesticidas em helmintos parasitos. O presente estudo investigou, em condições experimentais, os efeitos morfológicos no trematódeo E. paraensei após a exposição ao herbicida Roundup®, em concentrações abaixo das recomendadas para a utilização agrícola. A microscopia eletrônica de varredura (MEV) mostrou após duas horas de exposição, alterações no tegumento, como enrugamento, contração e descamação com perda de espinhos no colar peristômico e análise histopatológica evidenciou células do ceco alteradas, as glândulas vitelínicas com vacúolos e mudanças estruturais nas camadas musculares. Diminuição do conteúdo glicídico, principalmente no tecido conjuntivo, também foi observado. Considerando a predisposição à exposição a pesticidas agrícolas de N. squamipes infectado por E. paraensei, são necessários estudos para avaliar o impacto de tais resíduos frente aos helmintos e seus hospedeiros.

New morphological data of Litomosoides chagasfilhoi (Nematoda: Filarioidea) parasitizing Nectomys squamipes in Rio de Janeiro, Brazil / Novos dados morfológicos de Litomosoides chagasfilhoi (Nematoda: Filarioidea): parasitando Nectomys squamipes no Rio de Janeiro, Brasil

Abstract Litomosoides chagasfilhoi, originally described by Moraes Neto, Lanfredi & De Souza (1997) parasitizing the abdominal cavity of the wild rodent, Akodon cursor (Winge, 1887), was found in the abdominal cavity of Nectomys squamipes (Brants, 1827), from the municipality of Rio Bonito, Rio de Janeiro State, Brazil. This study led to addition of new morphological data and a new geographical distribution for this filarioid in Brazil. Several characters were detailed and emended to previous records of L. chagasfilhoi in N. squamipes, and confirming the original description in A. cursor: buccal capsule longer than wide with walls thinner than the lumen, right spicule slightly sclerotized, with membranous distal extremity slender, with a small tongue-like terminal portion, left spicule with handle longer than the blade, whose edges form large membranous wings folded longitudinally.

Resumo Litomosoides chagasfilhoi, originalmente descrito por Moraes Neto, Lanfredi & De Souza (1997) parasitando a cavidade abdominal do roedor silvestre Akodon cursor (Winge, 1887), foi encontrado na cavidade abdominal de Nectomys squamipes (Brants, 1827), no município de Rio Bonito, Estado do Rio de Janeiro, Brasil. Este estudo propiciou a adição de novos dados morfológicos e uma nova distribuição geográfica deste filarídeo no Brasil. Vários caracteres foram detalhados e adicionados ao registro anterior de L. chagasfilhoi em N. squamipes, e confirmando a descrição original em A. cursor: cápsula bucal mais alta do que larga com paredes mais finas que o lúmen, espículo direito ligeiramente esclerotizado, com extremidade distal membranosa mais estreita, com uma pequena porção terminal em forma de língua, espículo esquerdo com cabo mais longo do que a lâmina, cujas bordas formam grandes asas membranosas dobradas longitudinalmente.

Angiostrongylus cantonensis infection in molluscs in the municipality of São Gonçalo, a metropolitan area of Rio de Janeiro, Brazil: role of the invasive species Achatina fulica in parasite transmission dynamics

The aim of this study was to analyse the infection dynamics ofAngiostrongylus cantonensisin its possible intermediate hosts over two years in an urban area in the state of Rio de Janeiro where the presence ofA. cantonensis had been previously recorded in molluscs. Four of the seven mollusc species found in the study were exotic.Bradybaena similariswas the most abundant, followed byAchatina fulica, Streptaxissp., Subulina octona, Bulimulus tenuissimus, Sarasinula linguaeformisand Leptinaria unilamellata. Only A. fulicaand B. similariswere parasitised by A. cantonensis and both presented co-infection with other helminths. The prevalence of A. cantonensisin A. fulicawas more than 50% throughout the study. There was an inverse correlation between the population size ofA. fulicaand the prevalence of A. cantonensisand abundance of the latter was negatively related to rainfall. The overall prevalence of A. cantonensisin B. similariswas 24.6%. A. fulicawas the most important intermediary host of A. cantonensisin the studied area andB. similariswas secondary in importance for A. cantonensistransmission dynamics.

New records of three species of nematodes in Cerdocyon thous from the Brazilian Pantanal wetlands / Novos registros de três espécies de nematoides em Cerdocyon thous do Pantanal brasileiro

We report the occurrence of nematodes collected from the gut of roadkilled crab-eating foxes (two adult males and one juvenile female), Cerdocyon thous (Linnaeus, 1766), found on the BR 262 highway in Mato Grosso do Sul state, Brazil in 2011. Three helminth species were identified: Ancylostoma buckleyi, Pterygodermatites (Multipectines) pluripectinata, and Ascaridia galli. These nematodes are reported for the first time to infect C. thous from the Brazilian Pantanal wetlands, thereby expanding their geographical distribution.

Este estudo relata a ocorrência de nematoides coletados no sistema digestório de cachorros-do-mato Cerdocyon thous (Linnaeus, 1766) encontrados atropelados na rodovia BR 262, no Estado do Mato Grosso do Sul, Brasil, em 2011. Três espécies foram identificadas: Ancylostoma buckleyi, Pterygodermatites (Multipectines) pluripectinata e Ascaridia galli. A ocorrência destes nematoides foi registrada pela primeira vez em C. thous no bioma Pantanal, ampliando a distribuição geográfica destes helmintos parasitos em C. thous.

Brazilian Angiostrongylus cantonensis haplotypes, ac8 and ac9, have two different biological and morphological profiles

Angiostrongylus cantonensis is the etiologic agent of eosinophilic meningoencephalitis in humans. Cases have been recorded in many parts of the world, including Brazil. The aim of this study was to compare the differences in the biology and morphology of two different Brazilian haplotypes of A. : ac8 and ac9. A significantly larger number of L1 larvae eliminated in the faeces of rodents at the beginning of the patent period was observed for ac9 haplotype and compared to the total of L1 larvae eliminated, there was a significant difference between the two haplotypes. The ac9 haplotype showed a significant difference in the proportion of female and male specimens (0.6:1), but the same was not observed for ac8 (1.2:1). The morphometric analysis showed that male and female specimens isolated from ac8 haplotype were significantly larger with respect to body length, oesophagus length, spicule length (male) and distance from the anus to the rear end (female) compared to specimens from ac9. The morphological analysis by light microscopy showed little variation in the level of bifurcations at the lateral rays in the right lobe of the copulatory bursa between the two haplotypes. The biological, morphological and morphometric variations observed between the two haplotypes agree with the observed variation at the molecular level using the cytochrome oxidase subunit I marker and reinforce the possible influence of geographical isolation on the development of these haplotypes.

Genetic and morphological characterisation of a new species of the genus Hysterothylacium (Nematoda) from Paralichthys isosceles Jordan, 1890 (Pisces: Teleostei) of the Neotropical Region, state of Rio de Janeiro, Brazil

Taking into account the difficulties of taxonomic identification of larval anisakid nematodes based on morphological characters, genetic analyses were performed, together with those usually applied, in order to identify anisakid larvae found in the flounder Paralichthys isosceles from the littoral of the state of Rio de Janeiro, Brazil. The analysis of 1,820 larvae revealed a new species, similar to Hysterothylacium MD, Hysterothylacium 2, Hysterothylacium KB and Hysterothylacium sp regarding the absence of the larval tooth, an excretory pore situated below the nerve ring level, and slender lateral alae. Moreover, the new species differs from Hysterothylacium fortalezae and Hysterothylacium reliquens with regard to the number and size of spines present on the tail end and from Hysterothylacium patagonicus by the absence of interlabia. The maximum parsimony and neighbour joining tree topologies based on the 18S ribosomal DNA gene, complete internal transcribed spacer region and cytochrome oxidase 2 (COII) gene demonstrated that the Brazilian larvae belong to Raphidascarididae and represent a unique genetic entity, confirmed as a new Hysterothylacium species. Furthermore, the new species presents COII genetic signatures and shares polymorphisms with Raphidascarididae members. This is the first description of a new anisakid species from Brazil through the integration of morphological and molecular taxonomy data.

First report of Angiostrongylus cantonensis (Nematoda: Metastrongylidae) in Achatina fulica (Mollusca: Gastropoda) from Southeast and South Brazil

The rat lungworm Angiostrongylus cantonensis is a worldwide-distributed zoonotic nematode that can cause human eosinophilic meningoencephalitis. Here, for the first time, we report the isolation of A. cantonensis from Achatina fulica from two Brazilian states: Rio de Janeiro (specifically the municipalities of Barra do Piraí, situated at the Paraiba River Valley region and São Gonçalo, situated at the edge of Guanabara Bay) and Santa Catarina (in municipality of Joinville). The lungworms were identified by comparing morphological and morphometrical data obtained from adult worms to values obtained from experimental infections of A. cantonensis from Pernambuco, Brazil, and Akita, Japan. Only a few minor morphological differences that were determined to represent intra-specific variation were observed. This report of A. cantonensis in South and Southeast Brazil, together with the recent report of the zoonosis and parasite-infected molluscs in Northeast Brazil, provide evidence of the wide distribution of A. cantonensis in the country. The need for efforts to better understand the role of A. fulica in the transmission of meningoencephalitis in Brazil and the surveillance of molluscs and rodents, particularly in ports, is emphasized.

Achatina Fulica como hospedeiro intermediário de nematódeos de interesse médico-veterinário em Goiás, Brasil / Achatina fulica as an intermediate host of nematoda of medical-veterinary interest in Goiás, Brazil

Achatina fulica, também conhecido como caramujo africano, é um molusco terrestre que pode atuar como hospedeiro intermediário de vários helmintos, entre eles alguns com importância médica e veterinária como Angiostrongylus cantonensis e Angiostrongylus costaricensis, nematódeos responsáveis pela meningoencefalite eosinofílica e pela angiostrongilose abdominal, respectivamente. Este estudo objetivou conhecer a distribuição deste molusco no estado de Goiás e pesquisar a ocorrência de larvas de nematódeos de interesse parasitológico. Detectado, inicialmente, em 2003 no município de Morrinhos, A. fulica teve sua distribuição geográfica ampliada e encontra-se atualmente presente em 39,5por cento, dos municípios de Goiás. A pesquisa da helmintofauna,realizada pela técnica de digestão artificial das amostras obtidas em Caldas Novas, Morrinhos e BelaVista de Goiás, resultou no encontro de larvas de Aelurostrongylus abstrusus (prevalência de 35por cento), Rhabditis sp. (47,5por cento), Strongyluris sp. (15por cento) e de outros metastrongilídeos (2,5por cento). Este estudo ampliou o conhecimento da distribuição geográfica de A. fulica em Goiás e reforçou a participação deste molusco em ciclos biológicos de helmintos, indicando a necessidade de controle e vigilância epidemiológica em áreas urbanas com grande densidade deste molusco em razão da facilidade de contato com as populações humanas e de animais domésticos, o que propicia a transmissão de zoonoses.

The effect of early infection with Echinostoma paraensei on the interaction of Schistosoma mansoni with Biomphalaria glabrata and Biomphalaria tenagophila

Infection caused by the trematode Echinostoma paraensei has been shown to interfere in the natural resistance to infection by Schistosoma mansoni. Biomphalaria glabrata is susceptible to infection, while Taim isolate Biomphalaria tenagophila is resistant to infection by S. mansoni. These two snail species were assessed for infection with E. paraensei two days after exposure to S. mansoni miracidia. The number of B. tenagophila and B. glabrata infected with E. paraensei was lower in co-infected group, suggesting an antagonistic relationship. B. glabrata showed an increase in its susceptibility to S. mansoni, whereas B. tenagophila maintained its refractoriness to S. mansoni infection. Weekly comparisons made between the E. paraensei cercariae released from B. tenagophila and B. glabrata mono-infected snails revealed no quantitative differences. In contrast, S. mansoni cercariae released were higher in the B. glabrata co-infected group. Mortality rates were significantly greater in both species pertaining to co-infected group and unexpected mortalities were also observed in B. tenagophila exposed only to S. mansoni miracidia. Our study revealed that the B. tenagophila Taim isolate is susceptible to E. paraensei infection, although infection did not alter its resistance to S. mansoni infection.

Notes on human cases of cystic echinococcosis in Peru

Cystic echinococcosis (CE) is a high prevalent zoonosis in the central and southern Peruvian Andes. Serum samples (n50)frompatients presenting presumptive clinical and radiological diagnosis of CE (group 1), were tested for antibodies against Echinococcus granulosus metacestode using Arc-5 double diffusion assay (DD5), immunoelectrophoresis (IEF), and immunoelectrotransfer blot (EITB) techniques. Serum samples (n18) from patients presenting other parasite infections (paragonomiasis, cysticercosis, and fascioliasis) or healthy blood donors (n15), were designated as control groups. The overall sensitivity of the tests was of 94 percent (DD5 and IEF tests) or 96 percent (EITB test). Only patients from group 1 were seropositive for CE. Polypeptides of 21, 31, and 48 kDa were considered positive for CE. Based on these results, this study demonstrates that CE also occurs in other coastal departments (Piura, Ancash, Ica, Arequipa, and Tacna) besides Lima.

Fatores sócio-culturais e éticos relacionados com os processos de diagnóstico da esquistossomíase mansônica em área de baixa endemicidade / Socio-cultural and ethical factors involved in the diagnosis of schistosomiasis mansoni in an area of low endemicity

Foram realizados em Sumidouro, Rio de Janeiro, Brasil, município endêmico para a esquistossomíase, cinco inquéritos parasitológicos anuais e um sorológico, baseados nas técnicas de Kato-Katz, sedimentação espontânea e western blot. Avaliou-se ainda a interveniência de fatores sociais, culturais e éticos na aplicação de tais métodos junto à comunidade. A possibilidade de opção foi decisiva para a participação das pessoas. As prevalências pela coproscopia foram: 11,6 por cento (1995); 8,8 por cento (1996); 12,2 por cento (1998); 5,9 por cento (1999); 3,2 por cento (2000). No ano de realização da sorologia, os resultados dos exames laboratoriais associados às informações sobre a transmissão, o acompanhamento clínico dos infectados e seus históricos de tratamento, geraram um procedimento diagnóstico nomeado coprosoroepidemiologia que refletiu mais precisamente a prevalência local. Confirmou-se que a vigilância epidemiológica evitaria o recrudescimento da prevalência. A substituição de Biomphalaria glabrata por Melanoides tuberculata no principal foco de transmissão, contribuiu para a queda acentuada dos índices de infecção.

Changes on Schistosoma mansoni (Digenea: Schistosomatidae) worm load in Nectomys squamipes (Rodentia: Sigmodontinae) concurrently infected with Echinostoma paraensei (Digenea: Echinostomatidae)

The water rat, Nectomys squamipes, closely involved in schistosomiasis transmission in Brazil, has been found naturally infected simultaneously by Schistosoma mansoni and Echinostoma paraensei. Laboratory experiments were conducted to verify parasitic interaction in concurrent infection. It was replicated four times with a total of 42 water rats and essayed two times with 90 mice pre-infected with E. paraensei. Rodents were divided into three groups in each replication. A wild strain recently isolated from Sumidouro, RJ, and a laboratory strain of S. mansoni from Belo Horizonte (BH) was used. Rats infected with E. paraensei were challenged 4 weeks later with S. mansoni and mice 2 or 6 weeks after the infection with S. mansoni. Necropsy took place 8 weeks following S. mansoni infection. The N. squamipes treatment groups challenged with S. mansoni RJ strain showed a significant decrease (80 and 65 percent) in the S. mansoni parasite load when compared with their respective control groups. There was a significant change or no change in the hosts challenged with the BH strain. The persistence time of E. paraensei within host was extended in relation to control groups, with a consequent enhancement of the number of recovered worm. An E. paraensei strain-specific influence on S. mansoni parasitism is reported. This paper presents some experimental data about this interaction in N. squamipes and Mus musculus

Susceptibility of Nectomys rattus (Pelzen, 1883) to experimental infection with Schistosoma mansoni (Sambon, 1907): a potential reservoir in Brazil

The aim of the present research was to evaluate the potential of Nectomys rattus, the "water rat", to develop Schistosoma mansoni infection. Comparison with N. squamipes was carried out. Both species of rodents were submitted to transcutaneous infection using different infective cercariae loads: 50, 100 or 500. N. rattus showed high susceptibility to S. mansoni, with an infection rate of 71 per cent. Rodents were able to excrete viable eggs of S. mansoni in the feaces during all infection period. For both species, the small intestine, followed by the liver and the large intestine, presented the highest concentration of eggs among the surveyed organs. Infection caused no animal death. Moreover, N. rattus accomplished the parasite's life cycle, by infecting the snails Biomphalaria glabrata and later Mus musculus. These evidences indicate that both N. rattus, as for N. squamipes are potential reservoirs for schistosomiasis in Brazil. Considering the fact that N. rattus and N. squamipes exist in the same natural ecosystems of S. mansoni, we suggest that these rodents must be regarded as influencial factors in epidemiology surveys.

Evaluation of the resistance to Schistosoma mansoni infection in nectomys squamipes rodentia: cricetidae a natural host of infection in Brazil

O desenvolvimento de resistencia em tres fases do transcurso de uma infeccao ativa (fase pre-ovular, aguda e cronica inicial) foi estudada comparando-se o numero total de vermes adultos recuperados no grupo reinfectado e o somatorio dos grupos controles. Demonstrou-se que o N. squamipes nao foi capaz de desenvolver resisitencia nas condicoes testadas e que ao contrario, a reinfeccao no periodo pre-ovular do parasito levou o roedor a apresentar o fenomeno de facilitacao, com reducao da resistencia natural e aumento da carga parasitaria. Esses resultados sugerem a existencia de outras formas de imunidade, distintas da imunidade concomitante, segundo o modelo empregado.

Comparative study on the localization of adult Schistosoma mansoni worms in albino mice anesthetized with pentobarbital sodium, ether or chloroform

The effect of anesthetic drugs on the localization of adult worms in albino mice was compared. The animals with 56 days of infection were anesthetized with pentobarbital sodium, ether or chloroform. Perfusion was carried out immediately after, recovering the worms and classifying them in relation to their localization on the liver or portal vein and the mesenteric veins. Our results showed that pentobarbital sodium produced a greater displacement of the worms to the liver (89) than ether (76) and chloroform (34) did, when compared to the control group (22). The difference between pentobarbital sodium and ether was significant (p < 0.05). We suggest that anesthetic drugs may not be used in studies on the distribution of adult worms in several hosts.

Nectomys squamipes (Rodentia: Cricetidae) as an experimental model for schistosomiasis mansoni

Twenty specimens of Nectomys squamipes born in captivity, were infected with 500 cercariae by the transcutaneous route. Coprologic examinations were carried out from the 5th to 23rd week after infection. On the 7th, 8th, 12th, 16th, and 23rd weeks the animals were sacrificed and perfused. The oogram was performed in segments of the small intestine (proximal, medial and distal portions) and the large intestine. The average pre-patent period was of 42 days. The average number of eggs varied from 350 on 6th week, to 800 on the 13th. From the 14th week on, the average number of eggs eliminated was lower than 50 per gram of feces. The recovery of worms kept steady on the 7th, 8th, and 12th week (16.85%; 15.45% and 11.95%), decreasing to 7.70% on the 16th week and 8.45% on the 23rd week. The proportion of male/female worms was about the same on the first two weeks, but from the 12th week on, the proportion was: 1,4/1 on the 12th week; 2,5/1 on the 16thweek and 1,8/1 on the 23rd weekThese observations suggest that N. squamipes may used as an experimental model for schistosomiasis mansoni, to wich it develops resistance mechanism, useful for immunity studies