Intermediate and definitive hosts of wild Schistosoma mansoni: ecological niche modeling of hosts in low endemicity areas.

The relationship between the environment and animal life began to be seen as an important tool to help control zoonoses. Climate variations lead to changes in the environment, which can influence the spatial distribution of species and, consequently, the spread of diseases to humans. Considered the main non-human definitive host species of Schistosoma mansoni in Brazil, the wild rodent Nectomys squamipes plays an important role as a reservoir in maintaining the schistosomiasis cycle in the absence of humans. This study demonstrates the results of ecological niche modeling of intermediate and definitive wild hosts of S. mansoni in the Regional Health Superintendence of Barbacena (Minas Gerais State), which has registered 31 municipalities, 80% of which are classified as endemic for parasitosis. Environmental variables associated with the distribution of each species were used based on information from the scientific collections of Global Biodiversity Information Facility (GBIF) and Species Link to project the ecological niche model in the geographic space. Abiotic variables such as the mean annual temperature, isothermality, and precipitation seasonality were obtained from World Clim. Ecological niche modeling of the wild host, N. squamipes, revealed the occurrence of the species in geographic overlap with the Biomphalaria species. Knowing the influence of bioclimatic variables and identifying favorable conditions for the establishment, occurrence, and distribution of species are important information for developing strategic actions for the surveillance and control of this endemic species. The presence of the definitive wild host needs to be considered by control programs of schistosomiasis.

Intermediate and definitive hosts of wild Schistosoma mansoni: ecological niche modeling of hosts in low endemicity areas

ABSTRACT The relationship between the environment and animal life began to be seen as an important tool to help control zoonoses. Climate variations lead to changes in the environment, which can influence the spatial distribution of species and, consequently, the spread of diseases to humans. Considered the main non-human definitive host species of Schistosoma mansoni in Brazil, the wild rodent Nectomys squamipes plays an important role as a reservoir in maintaining the schistosomiasis cycle in the absence of humans. This study demonstrates the results of ecological niche modeling of intermediate and definitive wild hosts of S. mansoni in the Regional Health Superintendence of Barbacena (Minas Gerais State), which has registered 31 municipalities, 80% of which are classified as endemic for parasitosis. Environmental variables associated with the distribution of each species were used based on information from the scientific collections of Global Biodiversity Information Facility (GBIF) and Species Link to project the ecological niche model in the geographic space. Abiotic variables such as the mean annual temperature, isothermality, and precipitation seasonality were obtained from World Clim. Ecological niche modeling of the wild host, N. squamipes, revealed the occurrence of the species in geographic overlap with the Biomphalaria species. Knowing the influence of bioclimatic variables and identifying favorable conditions for the establishment, occurrence, and distribution of species are important information for developing strategic actions for the surveillance and control of this endemic species. The presence of the definitive wild host needs to be considered by control programs of schistosomiasis.

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.

A survey of freshwater and terrestrial snails in a predominantly urban municipality of Rio de Janeiro State, Brazil, with emphasis on human parasites vectors.

Many snail species act as intermediate hosts of helminths that transmit diseases to humans and animals, such as schistosomiasis and angiostrongyliasis. São Gonçalo, a mostly urban municipality in Rio de Janeiro State, Brazil, has undergone fundamental environmental impacts, which favor the establishment of a range of diseases, for which snails act as the intermediate hosts of the etiological agents. In the present study, freshwater and terrestrial snail populations were surveyed in different environments within five city districts, and the presence of helminths was determined in the collected specimens. A total of 287 individuals were collected, six species from freshwater environment, Pomacea sp. (Ampullariidae), Melanoides tuberculata (Thiaridae), Biomphalaria tenagophila (Planorbidae), Dysopeas muibum (Subulinidae), Physa marmorata, and Physa acuta (Physidae), and two from terrestrial environment, Achatina fulica (Achatinidae) and Bradybaena similaris (Bradybaenidae). Snails were found in only two districts, Centro, an urban area, and Ipiiba, a rural area. Thirteen percent of the specimens of A. fulica eliminated larvae of the nematode Angiostrongylus cantonensis. None of the analyzed freshwater snails contained helminths.The most abundant and frequent snails were B. tenagophila, M. tuberculataand A. fulica, and the latter two species are exotic. The disturbance and degradation of natural areas adjacent to residential zones favor the proliferation of helminths, jeopardizing the local residents health. The abundance of A. fulica and B. tenagophila in the study area reinforces the need for a continuous and systematic monitoring of the snail fauna in this region.

First records of molluscs naturally infected with Angiostrongylus cantonensis (Nematoda: Metastrongyloidea) in Northeastern Brazil, including new global records of natural intermediate hosts.

Human neural angiostrongyliasis is an emerging infectious disease caused by nematode Angiostrongylus cantonensis. The present study investigated the presence of Angiostrongylus spp. in terrestrial molluscs collected from the following areas in the Metropolitan Region of Aracaju, Sergipe State, Brazil: Barra dos Coqueiros, Nossa Senhora do Socorro, Sao Cristovao and Aracaju. In total, 703 specimens representing 13 mollusc species were screened for Angiostrongylus spp. Larvae of Angiostrongylus spp. were found in three species. Larvae recovered from Achatina fulica were used for experimental infection in Wistar rats (Rattus norvegicus). For specific identification of nematodes, the mitochondrial cytochrome c oxidase subunit I (COI) was sequenced from both larvae and adults recovered from molluscs and rats, respectively. Infection with A. cantonensis was detected in all municipalities and in the following three host species: Bulimulus tenuissimus, Cyclodontina fasciata (Barra dos Coqueiros), and A. fulica (Aracaju, Nossa Senhora do Socorro and Sao Cristovao). Co-infections were also found with Caenorhabditis sp. and Strongyluris sp. larvae. This is the first study of the helminth fauna associated with the terrestrial malacofauna in Sergipe State, and confirms that these three snail species are involved in the transmission of A. cantonensis in the state. In addition, B. tenuissimus and C. fasciata are newly reported natural hosts of the parasite.

Morphological effects on helminth parasites caused by herbicide under experimental conditions.

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.

Bulimulus tenuissimus (mollusca) as a new potential host of Angiostrogylus cantonensis (nematoda), a histological and metabolic study.

The terrestrial gastropod Bulimulus tenuissimus is widespread in South America. It is an intermediate host of many parasites, but there are no records of infection of this snail by Angiostrongylus cantonensis, despite the occurrence of this parasite and angiostrongyliasis cases in the same areas in which B. tenuissimus occurs. For this reason, it is important investigate the susceptibility of B. tenuissimus to A. cantonensis-infection, since it can be used as intermediate host of A. cantonensis, increasing the list of terrestrial gastropods that infect wild and domestic animals and humans with this parasite. The purpose of this study was to evaluate the susceptibility of B. tenuissimus to experimental infection with L1 larvae of A. cantonensis. The snails were exposed to 1200 L1 larvae and it was possible observe many developing larvae in the cephalopedal mass and mantle tissues, with intense hemocyte infiltration and collagen deposition, but no typical granuloma structures were formed. The glucose content and lactate dehydrogenase activity in the hemolymph varied, indicating an increase of anaerobic energy metabolism in the middle of infection, but with a tendency to return to normal values at the end of pre-patent period. This was corroborated by the marked reduction in the glycogen content in the cephalopedal mass and digestive gland in the first and second week after exposure, followed by a slight increase in the third week. The content of pyruvic acid in the hemolymph was 14.84% lower at the end of pre-patent period, and oxalic acid content was 41.14% higher. These results indicate an aerobic to anaerobic transition process. The PAS reaction showed a large amount of glycogen inside the developing larvae and muscular tissues of the cephalopedal mass, indicating that despite the high consumption of this polysaccharide by the parasite, the snail is able to maintain its energy metabolism based on carbohydrates. The results reveal that B. tenuissimus is a robust host, which can live with the developing larvae of A. cantonensis and overcome the metabolic damages resulting from parasitism.

Morphological effects on helminth parasites caused by herbicide under experimental conditions

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 pesticides 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.(AU)

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.(AU)

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.

Avaliação bioquímica, hematológica e histopatológica da infecção experimental por Angiostrongylus cantonensis no hospedeiro definitivo Rattus norvegicus (Wistar) e estudo da interação Angiostrongylus cantonensis / Echinostoma paraensei no hospedeiro intermediário Biomphalaria glabrata / Biochemical, hematological and histopathological evaluation of experimental infection with A. cantonensis in Rattus norvegicus definitive host (Wistar) and study the interaction A. cantonensis / Echinostoma paraensei the intermediate host Biomphalari

A meningite eosinofílica é uma doença caracterizada pelo aumento de eosinófilos no líquidocefalorraquidiano (LCR), cuja causa mais comum é a invasão do sistema nervoso central porhelmintos. Entre os helmintos, destaca-se o Angiostrongylus cantonensis. O roedor Rattusnorvegicus é o hospedeiro natural definitivo e o homem atua como hospedeiro acidental e que podese infectar através da ingestão de moluscos crus ou mal cozidos ou alimentos contaminados com alarva L3. Recentemente, no Brasil houve quatro casos de meningite eosinofílica, devido à ingestãoou manipulação de Achatina fulica infectada. Foi realizado uma avaliação das alteraçõesmetabólicas, fisiológicas e histopatológicas em R. norvegicus experimentalmente infectados com100 larvas L3 de A. cantonensis e o estudo do efeito da infecção concomitante por Echinostomaparaensei e A. cantonensis sobre a atividade das aminotransferases ALT e AST, na concentração deproteínas totais, ácido úrico, ureia e análise histopatológica para compreender o efeito da infecçãoconcomitante em Biomphalaria glabrata. Os resultados obtidos demonstraram que a infecçãocausada por A. cantonensis em R. norvegicus promoveu alterações metabólicas hepáticas ehistopatológicas, caracterizadas pelo aumento da atividade das enzimas ALT, AST, GGT e ALKP,alteração no metabolismo glicídico, presença de infiltrado inflamatório, alterações hematológicassignificativas, além disso promoveu alterações histopatológicas no parênquima pulmonardemonstraram nos roedores a ocorrência de áreas de necrose e extensa fibrose, podendo estardiretamente relacionada com o desenvolvimento de hipóxia celular...

Eosinophilic meningitis is a disease characterized by increased eosinophils in the cerebrospinalfluid (CSF), which is the most commonly caused by invasion of the central nervous system byhelminths, as occurs in Angiostrongylus cantonensis infections. The rodent Rattus norvegicus is thedefinitive natural host and humans act as accidental hosts and can become infected by eating raw orundercooked snails or food contaminated with infective L3 larvae. Recently in Brazil there havebeen four cases of eosinophilic meningitis due to ingestion of infected Achatina fulica. Anevaluation of metabolic, physiological and pathological changes in R. norvegicus experimentallyinfected with 100 L3 larvae of A. cantonensis and study the effect of co-infection with Echinostomaparaensei and A. cantonensis on the activity of aminotransferases ALT and AST was performed inthe concentration total protein, uric acid, urea and histopathologic analysis to understand the effectof co-infection in Biomphalaria glabrata. The results showed that the infection caused by A.cantonensis in R. norvegicus promoted histopathological changes in liver metabolism ischaracterized by increased activity of ALT, AST, GGT and ALKP enzymes in glucose metabolism,inflammatory infiltrate, hematological changes significant in addition in addition histopathologicalalterations in lung parenchyma in rodents have shown the occurrence of extensive areas of necrosisand fibrosis, which can be directly related to the development of cellular hypoxia. The infectedsnails showed altered levels of aminotransferases and increased excretion of nitrogen products,histopathological findings showed a change in the distribution of A. cantonensis in the presence ofE. paraensei, indicating that the presence of this trematode may interfere with the dynamics of A.cantonensis...

Biochemical and histological changes in liver of Nectomys squamipes naturally infected by Schistosoma mansoni / Alterações na bioquímica e histologia do fígado de Nectomys squamipes naturalmente infectado por Schistosoma mansoni

The South American water rat Nectomys squamipes is a wild mammal reservoir of Schistosoma mansoni in Brazil. In the present study, wild rodents were collected in the field and categorized into two groups: infected and uninfected by S. mansoni. Blood was collected to analyze changes in the serum glucose level (mg/dL) and liver fragments were used to determine the hepatic glycogen content (mg of glucose/g tissue). The histological examination showed inflammatory granulomatous lesions in different phases of development in the liver of rodents naturally infected with S. mansoni, in some cases with total or partial occlusion of the vascular lumen. Early lesions were characterized by the presence of inflammatory infiltrate around morphologically intact recently deposited eggs. Despite the significance of these histological lesions, the biochemical changes differed in extent. N. squamipes naturally infected by S. mansoni showed no variation in hepatic glycogen reserves. These findings were accompanied by a significant increase in plasma glucose contents, probably as a consequence of amino acids deamination, which are degraded, resulting in the formation of intermediates used as precursors for the glucose formation, without compromising the reserves of liver glycogen. In the wild, naturally infected N. squamipes can maintain S. mansoni infections without undergoing alterations in its carbohydrate metabolism, which minimizes the deleterious effects of S. mansoni.

Nectomys squamipes é um mamífero silvestre reservatório de Schistosoma mansoni no Brasil. No presente estudo, os roedores silvestres, colhidos no campo, foram classificados em dois grupos: infectado e não infectado por S. mansoni. O sangue foi colhido para análise da alteração no nível de glicose sérico (mg/dL) e fragmentos de fígado foram usados para determinar o conteúdo de glicogênio hepático (mg de glicose/g tecido). A análise histológica demonstrou lesões granulomatosas em diferentes fases de desenvolvimento no tecido hepático dos roedores naturalmente infectados com S. mansoni, localizados principalmente na região periportal, com total ou parcial oclusão do lúmen vascular. As lesões foram caracterizadas por presença de infiltrado inflamatório ao redor de ovos morfologicamente intactos recentemente depositados. Apesar da grande significância das lesões histológicas, as alterações bioquímicas não diferiram no mesmo grau. N. squamipes naturalmente por S. mansoni não apresentaram variação na reserva de glicogênio hepático. Esses achados foram acompanhados pelo aumento significativo nos conteúdos de glicose plasmática, provavelmente como consequência ao processo desaminativo de aminoácidos, que passam a ser degradados notadamente para a formação de glucose, sem contudo comprometer a reserva de glicogênio hepático. Em condições naturais a infecção de S. mansoni pode ser mantida usando N. squamipes como hospedeiro definitivo, sem alterações significativas nos conteúdos de glicogênio hepático, minimizando os efeitos deletérios causados por S. mansoni nos roedores N. squamipes naturalmente infectados.

Aerobic to anaerobic transition in Biomphalaria glabrata (Say, 1818) infected with different miracidial doses of Echinostoma paraensei (Lie and Basch, 1967) by high-performance liquid chromatography.

The glucose content in the hemolymph and glycogen content in the digestive gland-gonad complex (DGG) and cephalopedal mass of Biomphalaria glabrata exposed to different parasite doses (5 and 50 miracidia) of Echinostoma paraensei as well as the activity of lactate dehydrogenase were evaluated. HPLC (high-performance liquid chromatography) analyses were also performed to determine the concentrations of four organic acids (oxalic, succinic, pyruvic and lactic) present in the hemolymph of infected and uninfected snails, to better understand the effect of infection on the host's energetic/oxidative metabolism. The snails were dissected 1-4 weeks after infection to collect the hemolymph and separate the tissues. There was alteration in the glycemia of the snails at both parasite doses, with a significant increase of glycemia from of the third week after infection in comparison to the control group. Changes were also observed in the lactate dehydrogenase activity, with increased activity as the infection progressed. In parallel, there was a decrease in the glycogen content in the storage tissues, with a markedly greater reduction in the digestive gland-gonad complex (larval development site) in comparison with the cephalopedal mass. Additionally, the infection by both miracidial doses resulted in an increase of oxalic and lactic acid levels, as well as in a decline of piruvic and succinic acid levels in B. glabrata, thus explaining the reduction of the oxidative decarboxylation rate in the tricarboxylic acid cycle and acceleration of the anaerobic degradation of carbohydrates in the snails, through lactic fermentation, which is essential to ensure energy supply and success of the infection.

Biochemical and histological changes in liver of Nectomys squamipes naturally infected by Schistosoma mansoni.

The South American water rat Nectomys squamipes is a wild mammal reservoir of Schistosoma mansoni in Brazil. In the present study, wild rodents were collected in the field and categorized into two groups: infected and uninfected by S. mansoni. Blood was collected to analyze changes in the serum glucose level (mg/dL) and liver fragments were used to determine the hepatic glycogen content (mg of glucose/g tissue). The histological examination showed inflammatory granulomatous lesions in different phases of development in the liver of rodents naturally infected with S. mansoni, in some cases with total or partial occlusion of the vascular lumen. Early lesions were characterized by the presence of inflammatory infiltrate around morphologically intact recently deposited eggs. Despite the significance of these histological lesions, the biochemical changes differed in extent. N. squamipes naturally infected by S. mansoni showed no variation in hepatic glycogen reserves. These findings were accompanied by a significant increase in plasma glucose contents, probably as a consequence of amino acids deamination, which are degraded, resulting in the formation of intermediates used as precursors for the glucose formation, without compromising the reserves of liver glycogen. In the wild, naturally infected N. squamipes can maintain S. mansoni infections without undergoing alterations in its carbohydrate metabolism, which minimizes the deleterious effects of S. mansoni.

Susceptibility of a Brazilian wild rodent isolate of Schistosoma mansoni to praziquantel in mice.

The therapeutic effects of praziquantel (PZQ) against a Schistosoma mansoni isolate derived from Nectomys squamipes (isolate R) and a susceptible isolate (BH) were analyzed in Swiss mice by fecal egg counting, adult worm reduction and oogram pattern. Infected mice were orally administrated with 62.5mg/kg (group 1), 125mg/kg (group 2), 250mg/kg (group 3) and 500mg/kg (group 4), each dose divided over 3 days (49, 50 and 51 days after infection). The data were analyzed using one-way analysis of variance (ANOVA). In regard to isolate R, no fecal eggs were observed with 250 mg/Kg and 500 mg/kg (p<0.05), whereas BH excretion reached zero with all doses. Mean worm burden reduction was significantly (p<0.05) higher at the two highest concentrations, regardless of isolate. At 62.5mg/kg, the percentage of immature eggs varied from 17% (isolate R) to 38% (isolate BH). At 125 mg/kg, the percentage of immature eggs varied from 20% (isolate R) to 16% (isolate BH). At 250 mg/kg, immature eggs dropped significantly to 1% (isolate R) and 4% (isolate BH). At 500 mg/kg, no immature eggs were found in isolate R, whereas in BH was 8%. No dosage significantly (p>0.05) affected the percentage of mature eggs, regardless of isolate. There was a large increase (p<0.001) in the percentages of dead eggs in all treated groups of 62% and 64% in groups 3 and 4, respectively (isolate R). The percentage of dead eggs rose from 34% (group 1) to 58% (group 3) in isolate BH. Although group 4 showed lowest increase in the percentage of dead eggs (46%), it was higher (p<0.001) compared to the 8% in the control. Our findings indicate that the wild isolate from N. squamipes is susceptible to PZQ.

Influence of Echinostoma paraensei (Lie and Basch, 1967) infection on the calcium content in Biomphalaria glabrata (Say, 1818).

The calcium content in the hemolymph and shell of Biomphalaria glabrata (Say, 1818) was determined after exposure to different parasite burdens (5 and 50 miracidia) of Echinostoma paraensei (Lie and Basch, 1967). The snails were dissected 1, 2, 3, and 4 weeks after infection to collect the hemolymph and shell. An increase in calcemia was observed in snails infected with both miracidial doses. A significant decrease in the calcium ions in the shell was observed, coinciding with the calcemia peak in the hemolymph. This indicates greater mobilization of calcium between the shell and hemolymph to regulate the calcium content in the body when the snail is exposed to stress conditions, as has also been observed in some other infected snail species. The results obtained indicate that in this model, the calcium metabolism depends on the miracidial dose used.

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.

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.