Spurious infection by Calodium hepaticum (Bancroft, 1983) Moravec, 1982 and intestinal parasites in forest reserve dwellers in Western Brazilian Amazon

ABSTRACT Subsistence hunting is the main source of protein for forest reserve dwellers, contributing to the development of spurious infections by Calodium hepaticum, frequently associated with the consumption of the liver from wild mammals. The prevalence of infections by soil-transmitted helminths (STHs) and intestinal protozoa is considered an indicator of the social vulnerability of a country, besides providing information on habits, customs and quality of life of a given population. Intestinal parasites mostly affect poor rural communities with limited access to clean water and adequate sanitation. This study reports the results of a parasitological survey carried out in 2017 and 2019, in two municipalities (Xapuri and Sena Madureira) in Acre State. Stool samples were collected from 276 inhabitants. Upon receipt, each sample was divided into two aliquots. Fresh samples without preservative were processed and examined by the Kato-Katz technique. Samples fixed in 10% formalin were processed by the spontaneous sedimentation and the centrifugal sedimentation techniques. Calodium hepaticum eggs were found in three stool samples. The overall STH prevalence was 44.9%. The hookworm prevalence (19.2%) was higher than that of Ascaris lumbricoides (2.5%) and Trichuris trichiura (0.7%), an unexpected finding for municipalities belonging to the Western Brazilian Amazon. When considering parasites transmitted via the fecal-oral route, Endolimax nana and Entamoeba coli showed the highest positivity rates, of 13% and 10.9%, respectively. This study is the first report of spurious infection by C. hepaticum among forest reserve dwellers that consume undercooked liver of lowland pacas. Additionally, this is the first report of Blastocystis sp. in Acre State.

Effects of multiple doses of simvastatin and artesunate monotherapy on SCHISTOSOMA MANSONI adult worms during infection in hyperlidemic mice / Efectos de múltiples dosis de simvastatina y artesunato en monoterapia en gusanos adultos de SCHISTOSOMA MANSONI durante la infección en ratones hiperlidémicos / Efeitos de doses múltiplas de monoterapia com sinvastatina e artesunato em vermes adultos SCHISTOSOMA MANSONI durante a infecção em camundongos hiperlidêmicos

A single dose of simvastatin and of artesunate monotherapy cause damage to the reproductive system of schistosomes as well as severe tegumental damage in male worms recovered from mice fed high-fat chow. This study aims to investigate whether treatment with multipledose regimes may offer more antischistosomal activity advantages than single daily dosing in mice fed high-fat chow. For this purpose, nine weeks post-infection, Swiss Webster mice were gavaged with simvastatin (200 mg/kg) or artesunate (300 mg/kg) for five consecutive days and euthanized two weeks post-treatment. Adult worms were analyzed using brightfield microscopy, confocal microscopy and scanning electron microscopy, presenting damages caused by simvastatin and artesunate to the reproductive system of males and females as well as tegument alterations, including peeling, sloughing areas, loss of tubercles, tegumental bubbles and tegument rupture exposing subtegumental tissue. The overall findings in this study revealed the potential antischistosomal activity of simvastatin and artesunate against Schistosoma mansoni adult worms, in addition to showing that multiple doses of either monotherapy caused severe damage to the tegument.

Una sola dosis de simvastatina y de artesunato en monoterapia causa daño al sistema reproductivo de los esquistosomas, así como daño tegumental severo en gusanos machos recuperados de ratones alimentados con comida rica en grasas. Este estudio tiene como objetivo investigar si el tratamiento con regímenes de dosis múltiples puede ofrecer más ventajas de actividad antiesquistosomal que la dosis única diaria en ratones alimentados con comida rica en grasas. Para este propósito, nueve semanas después de la infección, los ratones Swiss Webster se alimentaron por sonda con simvastatina (200 mg / kg) o artesunato (300 mg / kg) durante cinco días consecutivos y se sacrificaron dos semanas después del tratamiento. Los gusanos adultos se analizaron utilizando campo claro microscopía, microscopía confocal y microscopía electrónica de barrido, presentando daños causados ​​por simvastatina y artesunato en el sistema reproductivo de machos y hembras, así como alteraciones del tegumento, incluyendo descamación, desprendimiento, pérdida de tubérculos, burbujas tegumentales y rotura del tegumento exponiendo tejido subtegumental. Los hallazgos generales de este estudio revelaron la posible actividad antiesquistosomal de la simvastatina y el artesunato contra los gusanos adultos de Schistosoma mansoni, además de mostrar que dosis múltiples de cualquiera de las dos monoterapia causaron daños graves al tegumento.

Uma única dose de sinvastatina e de monoterapia com artesunato causa danos ao sistema reprodutivo dos esquistossomos, bem como danos graves ao tegumento em vermes machos recuperados de camundongos alimentados com ração rica em gordura. Este estudo tem como objetivo investigar se o tratamento com regimes de múltiplas doses pode oferecer mais vantagens da atividade anti-esquistossomótica do que uma única dose diária em ratos alimentados com ração rica em gordura. Para tanto, nove semanas após a infecção, camundongos Swiss Webster foram inoculados com sinvastatina (200 mg / kg) ou artesunato (300 mg / kg) por cinco dias consecutivos e sacrificados duas semanas após o tratamento. Vermes adultos foram analisados ​​usando campo claro microscopia, microscopia confocal e microscopia eletrônica de varredura, apresentando danos causados ​​pela sinvastatina e artesunato ao sistema reprodutivo de homens e mulheres, bem como alterações do tegumento, incluindo descamação, áreas de descamação, perda de tubérculos, bolhas tegumentais e ruptura do tegumento com exposição de tecido subtegumentar. Os achados gerais deste estudo revelaram a potencial atividade anti-esquistossomótica da sinvastatina e do artesunato contra vermes adultos do Schistosoma mansoni, além de mostrar que doses múltiplas de ambas as monoterapias causaram danos graves ao tegumento.

Prebiotic effects of inulin extracted from burdock (Arctium lappa) in broilers / Efeito prebiótico da inulina extraída da bardana (Arctium lappa) em frangos de corte

The aim of this study was to evaluate the prebiotic effect of burdock (Arctium lappa) in commercial poultry. Four experiments were conducted to evaluate the performance parameters and the protection after challenge with Salmonella Enteritidis and Salmonella Kedougou, with and without Bifidobacterium probiotic. In two trials, the chickens were fed with flour burdock 1% during 42 days. In the other two, the chickens were fed with fructan extracted from burdock (inulin), by gavage, at a concentration of 100 mg/bird, during the first three days of life. The results showed that the broilers treated with burdock flour showed underperformed, with less weight gain from the second week, and the worst results in the fattening stage. The treated birds had diarrhea and impaired intestinal integrity. However, the groups treated with the flour had a lower rate of intestinal colonization by Salmonella Kedougou, after challenge. No statistically significant differences were detected in the performance parameters of broilers receiving the inulin, and the morphometric analysis showed no lesions in the intestinal villi. However, there was no protection in the challenge with Salmonella Enteritidis, regardless of association with probiotic. These results demonstrated that the manner of administration has influence on the prebiotic effect of burdock. The burdock flour was administered for 42 days, which may have influenced intestinal mucosal injury. Instead, the inulin was given only in the first three days, which may have been insufficient for protection against Salmonella. New experiments are needed to determine an able formulation for a protective effect, without negative impact on growth, weight gain and feed conversion of the supplemented animals.(AU)

Este projeto teve por objetivo avaliar o efeito prebiótico da bardana (Arctium lappa) em aves comerciais. Foram realizados quatro experimentos para avaliar os parâmetros zootécnicos e o grau de proteção após o desafio com Salmonella Kedougou e Salmonella Enteritidis, com e sem a adição de probióticos à base de Bifidobacterium. Em dois experimentos, as aves receberam a farinha de bardana 1% na ração, durante 42 dias. Nos outros dois, as aves receberam o frutano extraído da bardana (inulina), por gavagem, na concentração de 100 mg/ave, nos três primeiros dias de vida. Os resultados demonstraram que os frangos tratados com farinha de bardana apresentaram desempenho zootécnico inferior ao controle, com menor ganho de peso a partir da segunda semana e piores resultados na fase de engorda. As aves tratadas apresentaram diarreia e comprometimento da integridade intestinal. Em contrapartida, os grupos tratados com a farinha tiveram menor taxa de colonização intestinal por Salmonella Kedougou, após o desafio. Não foram detectadas diferenças estatisticamente significativas nos parâmetros zootécnicos dos frangos que receberam a inulina, e a análise morfométrica não evidenciou lesões nas vilosidades intestinais. No entanto, não houve proteção no desafio por Salmonella Enteritidis, independentemente da associação com probiótico. Esses resultados demonstraram que o modo de administração tem influência sobre o efeito prebiótico da bardana. A farinha de bardana foi administrada por 42 dias, o que pode ter causado a lesão da mucosa intestinal. Em contrapartida, a inulina foi administrada apenas nos primeiros três primeiros dias, o que pode ter sido insuficiente para proteção contra Salmonella. Novos experimentos são necessários para determinar uma formulação capaz de promover efeito protetor, sem impacto negativo no crescimento, ganho de peso e conversão alimentar dos animais suplementados.(AU)

Initial peptidomic profiling of Brazilian sea urchins: Arbacia lixula, Lytechinus variegatus and Echinometra lucunter

Sea urchins can be found throughout the Brazilian coast and are reported to be one of the major causes of marine accidents on the shoreline. Although not lethal, these accidents are reported to be extremely painful. In order to understand the toxinology of the Brazilian urchins, a peptidomic approach was performed aiming to characterize the naturally occurring peptides in both the coelomic fluid and the spine. Methods Animals were collected without gender distinction and samples of the coelomic fluid and spines extracted were analyzed by RP-HPLC and mass spectrometry for peptide de novo sequencing. Results Several peptides were identified either in the coelomic fluid or the spine extract (except for E. lucunter). The peptide sequences were aligned with public deposited sequences and possible functions were inferred. Moreover, some peptides can be cryptides, since their sequences were identified within functional proteins, for example thymosin from Strongylocentrotus purpuratus. Conclusions Although preliminary, the peptidomic approach presented here reports, for the first time, the abundance of novel biological molecules derived from these animals. The discovery of such molecules may be of potential biotechnological application, as described for other organisms; nevertheless, further studies are required.

Initial peptidomic profiling of Brazilian sea urchins: Arbacia lixula, Lytechinus variegatus and Echinometra lucunter

Background Sea urchins can be found throughout the Brazilian coast and are reported to be one of the major causes of marine accidents on the shoreline. Although not lethal, these accidents are reported to be extremely painful. In order to understand the toxinology of the Brazilian urchins, a peptidomic approach was performed aiming to characterize the naturally occurring peptides in both the coelomic fluid and the spine. Methods Animals were collected without gender distinction and samples of the coelomic fluid and spines extracted were analyzed by RP-HPLC and mass spectrometry for peptide de novo sequencing. Results Several peptides were identified either in the coelomic fluid or the spine extract (except for E. lucunter). The peptide sequences were aligned with public deposited sequences and possible functions were inferred. Moreover, some peptides can be cryptides, since their sequences were identified within functional proteins, for example thymosin from Strongylocentrotus purpuratus. Conclusions Although preliminary, the peptidomic approach presented here reports, for the first time, the abundance of novel biological molecules derived from these animals. The discovery of such molecules may be of potential biotechnological application, as described for other organisms; nevertheless, further studies are required.(AU)

Adaptation of the gill epithelium of an euryhaline fish, the guppy (Poecilia vivipara), to freshwater / Adaptação do epitélio branquial de peixes eurialinos, guaru (Poecilia vivipara), para água doce

The south-american euryhaline fish Poecilia vivipara (BLOCH; SNEIDER, 1801), the guppy, is found both in estuary and river waters, which suggests high adaptability to environments of different salinity. In this work we studied the adaptation of the interlamellar, bars and rakers epithelia of the gills of estuary fish to freshwater conditions. The results reveal that the gill epithelia of Poecilia vivipara can adjust itself to freshwater by decreasing the VP of mucous cells of the interlamellar epithelium and increase the volumetric proportion (VP) of chloride cells. However, there was no evidence of similar morphological alteration in the rakers region. The epithelia of the rakers appears to be part of a different compartment that is less sensitive to variation of salinity.

O peixe eurihalino sul-americano Poecilia vivipara (BLOCH; SNEIDER, 1801), o guppy, é encontrado tanto em estuários quanto em águas de rios, o que sugere uma alta adaptabilidade aos diferentes ambientes de salinidade. Neste trabalho, estudamos a adaptação do epitélio interlamelar, do arco e do rastelo das brânquias dos peixes de estuário de água doce. Os resultados revelam que o epitélio branquial de Poecilia vivipara pode ajustar-se à água doce, diminuindo a proporção volumétrica (PV) de células mucosas do epitélio interlamelar e aumentando a PV de células clorídricas. No entanto, não houve nenhuma evidência de alteração morfológica semelhante na região do rastelo branquial. O epitélio do rastelo branquial parece ser parte de um compartimento diferente que é menos sensível a variações de salinidade.

Hepatic stereology of acute schistosomiasis mansoni infection in C57BL/10 and CBA mice

Estudos prévios mostraram que o curso da infecção esquistossomótica experimental depende da constituição genética do hospedeiro. A fim de testar se linhagens de camundongos infectados por Schistosoma mansoni apresentam diferenças nos padrões de patologia durante a fase aguda, examinamos possíveis alterações nos hepatócitos, sinusóides e quantidade de fibrose, utilizando uma abordagem estereológica. As mudanças na organização hepática de camundongos fêmeas, adultas, das linhagens C57BL/10 e CBA, foram examinadas oito semanas após a infecção. A densidade de volume de hepatócitos Vv(h), sinusóides Vv(s) e fibrose Vv(fh) foram examinadas por determinação do ponto de contagem (sitema-teste M42) e video microscopia, por microscopia de luz. Em ambas linhagens de camundongo, Vv(h) e Vc(s) foram significamente reduzidas (p menor que 0,05) em relação ao grupo controle. Os maiores valores de Vv(fh) foram encontradas na linhagem C57BL/10. Demonstramos que a infecção esquistossomótica reduziu acentuadamente hepatócitos (linhagem CBA) sinusóides (linhagem C57BL10), enquanto a fibrose foi maior em C57BL10 do que CBA.

Hepatotrophic factors reduce hepatic fibrosis in rats / Fatores hepatotróficos reduzem a fibrose hepática em ratos

CONTEXT: Hepatic fibrosis occurs in response to several aggressive agents and is a predisposing factor in cirrhosis. Hepatotrophic factors were shown to stimulate liver growth and to restore the histological architecture of the liver. They also cause an improvement in liver function and accelerate the reversion of fibrosis before it progresses to cirrhosis. OBJECTIVE: To test the effects of hepatic fibrosis solution composed by amino acids, vitamins, glucose, insulin, glucagon and triiodothyronine on hepatic fibrosis in rats. METHODS: Fibrosis was induced in rats by gastric administration of dimethylnitrosamine (10 mg/kg) for 5 weeks. After liver biopsy, the rats received either hepatotrophic factors solution (40 mg/kg/day) or saline solution for 10 days by intraperitoneal injection. Blood samples and liver fragments were collected for hepatic function analysis, standard histopathology evaluation, and morphometric collagen quantification. RESULTS: Rats in the hepatotrophic factors group showed a decrease of the histopathological components of fibrosis and an increase of their hepatic mass (12.2 percent). There was no development of neoplasic lesions in both groups. Compared with the saline group, the hepatotrophic factors group also had a decrease of blood levels of hepatic-lesion markers (AST, ALT) and a decrease of collagen content in the portal spaces (31.6 percent) and perisinusoidal spaces (42.3 percent), as well as around the hepatic terminal vein (57.7 percent). Thus, hepatotrophic factors administration in the portal blood promoted a regenerative hepatic response, with an overall reduction of the volumetric density of collagen, improved hepatic function, and a general improvement in the histopathological aspects of fibrosis. CONCLUSION: Taken together, these results suggest the potential therapeutic use of this hepatotrophic factors solution to treat chronic liver diseases.

CONTEXTO: A fibrose hepática ocorre em resposta a diversos agentes agressores e é um fator predisponente da cirrose. Fatores hepatotróficos são conhecidos por estimular o crescimento hepático e restaurar a arquitetura histológica do fígado. Promovem, também, melhora na função hepática e aceleram a reversão da fibrose antes de sua progressão para cirrose. OBJETIVO: Testar os efeitos de uma solução de fatores hepatotróficos, composta por aminoácidos, vitaminas, glicose, insulina, glugacon e triiodotironina na fibrose hepática em ratos. MéTODOS: No presente estudo, a fibrose foi induzida em ratos pela administração de dimetilnitrosamina (10 mg/kg) durante 5 semanas. Após a biopsia do fígado, os ratos receberam a solução de fatores hepatotróficos (40 mg/kg/dia) ou solução salina por injeção intraperitonial, durante 10 dias. Amostras sanguíneas e fragmentos do fígado foram coletados para análise da função hepática, avaliação do critério histopatológico e quantificação morfométrica do colágeno. RESULTADOS: Os ratos do grupo fatores hepatotróficos demonstraram diminuição dos componentes histopatológicos da fibrose e aumento de massa hepática (12,2 por cento). Não houve o desenvolvimento de lesões neoplásicas em ambos os grupos. Comparado com o grupo de salina, no grupo fatores hepatotróficos também houve diminuição nos níveis dos marcadores sanguíneos de lesão hepática (AST e ALT), e diminuição da quantidade de colágeno nos espaços porta (31,6 por cento) e espaços perissinusoidais (42,3 por cento), assim como ao redor das veias terminais hepáticas (57,7 por cento). Assim, a administração de fatores hepatotróficos no sangue portal promoveu resposta regenerativa hepática, com redução da densidade volumétrica de colágeno, melhora na função hepática e melhora geral nos aspectos histopatológicos da fibrose. CONCLUSÃO: Juntos, estes resultados sugerem o potencial uso terapêutico desta solução de fatores hepatotróficos para tratar doenças hepáticas crônicas.

Anatomia e histologia gastrintestinal da garoupa-verdadeira Epinephelus marginatus (Lowe, 1834) (Teleostei, Serranidae) / Dusky grouper Epinephelus marginatus (Lowe, 1834) (Teleostei, Serranidae) gastrintestinal anatomy and histology

A garoupa-verdadeira (Epinephelus marginatus) é uma espécie de serranídeo com grande importância ecológica e boas perspectivas para o cultivo. A investigação da morfologia do trato digestório, associada à atividade alimentar, é fundamental para a compreensão da biologia dessa espécie e premissa básica para pesquisas sobre requerimentos nutricionais, desenvolvimento de rações e práticas adequadas de manejo alimentar. O presente trabalho descreve a anatomia e, por meio da microscopia de luz, as variações histológicas ao longo do tubo digestório de juvenis de Epinephelus marginatus, correlacionando a histologia de cada seguimento com as respectivas funções e o hábito alimentar. Verificou-se que essa espécie possui elevado número de tipos celulares ao longo do tubo digestório que estão intimamente relacionados com a resposta imunológica inata e adaptativa, permitindo o hábito alimentar detritívoro.

The dusky grouper (Epinephelus marginatus) is a serranida species with great ecological importance and good perspectives for rearing. The investigation of the digestive tract morphology associated to the feeding activity is essential for the understanding of the biology of this species and a basic premise for research on feed requirements, feed development and appropriate feeding methods. The present study describes the anatomy and histological variations along the digestive tract of Epinephelus marginatus juveniles associating the histology with function and feeding habit. It was verified that this species possesses a high number of different cellular types along the digestive tube intimately related with the innate and adaptative immunological responses.

Morphological study of adult male worms of schistosoma mansoni Sambon, 1907 by confocal laser scanning microscopy

Aiming to detail data obtained through brightfield microscopy (BM) on reproductive, excretory and digestive system, specimens of Schistosoma mansoni eight weeks old, were recovered from SW mice stained with Langeron's carmine and analysed under a confocal laser scanning microscope CLSM 410 (Carl Weiss). The reproductive system presented a single and locate testis, with intercommunications between the lobes without efferent duct. Supernumerary testicular lobe was amorphus and isolated from the normal ones. Collecting tubules (excretory ducts), followed by the excretory bladder, opening to the external media through the excretory pore, were observed at the posterior extremity of the body. In the digestive tract, a cecal swelling was noted at the junction that originates the single cecum. It was concluded that through confocal laser scanning microscopy, new interpretations of morphological structures of S. mansoni worms could be achieved, modifying adopted and current descriptions. The gonad consists of a single lobed testis, similar to that observed in some trematode species. Moreover, the same specimens can be observed either by BM or CLSM, considering that the latter causes only focal and limited damage in tissue structures.

Schistosoma mansoni Sambon 1907: morphometric differences between adult worms from sympatric rodent and human isolates

A computer software for image (IMAGE PRO PLUS, MEDIA CYBERNETICS) was utilized in male and females adult worms aiming the morphological characterization of Schistosoma mansoni samples isolated from a sylvatic rodent, Nectomys squamipes and humans in Sumidouro, Rio de Janeiro, Brazil and recovered from Mus musculus C3H/He. The following characters for male's testicular lobes were analyzed: number, area, density, larger and shorter diameter, longer and shorter axis and perimeter and extension; for females: area, longer and shorter axis, larger and smaller diameter and perimeter of the eggs and spine; oral and ventral suckers area and distance between them in both sex were determined. By the analysis of variance (one way ANOVA) significant differences (p<0.05) were observed in all studied characters, except for the density of testicular lobes. Significant differences (p<0.05) were detected for all characters in the female worms. Data ratify that sympatric isolates present phenotypic differences and the adult female characters are useful for the proper identification of S. mansoni isolates.

Enhancement of liver size by stimulation of intact rat liver with exogenous hepatotrophic factors

Objetivos: Confirmar observaçoes anteriores (PARRA e col.) que sugeriam a possibilidade de fazer crescer o fígado em animais intactos, por estímulo hepatotrófico exógeno, ultrapassando seu tamanho biologicamente pré-determinado. Material e Métodos: Dois grupos de fêmeas de ratos Wistar, foram injetadas diariamente na cavidade peritoneal (40ml/kg) por sete dias consecutivos com as seguintes soluçoes: GRUPO A (controle) - soluçao salina com carboximetilcelulose (CMC) a 0,25 por cento; GRUPO B - soluçao de fatores hepatotróficos exógenos constituída de glicose, aminoácidos, insulina, glucagon, vitaminas, eletrólitos, triiodotironina e CMC na mesma concentraçao do grupo controle. No oitavo dia os animais forma sacrificados e avaliados os seguinte parâmetros: variaçao da massa hepática e DNA total do fígado dos animais do grupo experimental em relaçao ao grupo controle. Resultados: Foi observado crescimento da massa hepática de 114,16 +- 7,9 por cento acima do esperado e aumento do DNA total hepático de 12,99 +- 0,46 mg para 20,17 por fígado (p=0.0002). Conclusao: O aumento do tamanho do fígado a partir de sua massa primitiva, estimulada por fatores hepatotróficos exógenos, pode vir a ter aplicaçoes em intre-vivos, criando maior massa hepática a ser dividida entre doador e receptor.

Reduction of liver mass due to malnutrition in rats: correlation with emaciation of animals and size of organs

We studied the effects of protein-energy malnutrition on the liver morphology of rats as compared to animal emaciation and to reduction in size of the organs not irrigated by splanchnic blood such as kidneys and spleen. The animals were divided into two groups, one of them fed ad libitum rate (N=10) and the other (N=14) receiving water but no food for 7 days, and the changes in animal weight, liver, kidney and spleen mass were determined. DNA and the protein/DNA ratio, as well as hepatocyte size, were determined in liver tissue. The liver decreased in mass (27.14 percent) at a significantly higher proportion (p<0.05) when compared to body emaciation (19.22 percent). Similar to the reduction in body weight, the masses of kidneys and spleen were reduced by 18.68 percent and 24.28 percent, respectively The reduction in liver mass occurred due to hypoplasia and atrophy, i.e., a decrease in hepatocyte number and size, respectively. We conclude that there is a preferential consumption of liver protein in protein-energy malnutrition which is suggested to result from the additive action of the effects of overall consumption of organic reserves due to malnutrition proper and to the reduction of the hepatotrophic stimulus.

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.

Natural infection of wild rodents by Schistosoma mansoni parasitological aspects

The evaluation of the role of rodents as natural hosts of Schistosoma mansoni was studied at the Pamparräo Valley, Sumidouro, RJ, with monthly captures and examination of the animals. Twenty-three Nectomys squamipes and 9 Akodom arviculoides with a shistosomal infection rate of 56.5% and 22.2% respectively eliminated a great majority of viable eggs. With a strain isolated from one of the naturally infected N. squamipes, we infected 75% of simpatric Biomphalaria glabrata and 100% of albino Mus musculus mice. The adult worms, isolated from N. squamipes after perfusion were located mainly in the liver (91.5%) and the mesenteric veins (8.5%). The male/female proportion was 2:1. The eggs were distributed on small intestine segments (proximal, medial and distal portions) and the large intestine without any significant differences in egg concentration of these segments. In A. arviculoides, the few eggs eliminated by the stools were viable and there was litlle egg retention on intestinal segments. Considering the ease to complete S. mansoni biological cycle in the Nectomys/Biomphalaria/Nectomys system under laboratory conditions, probably the same is likely to occur in natural conditions. In support to this hypotesis there are also the facts that human mansonic shistosomiasis has a very low prevalence in Sumidouro and endemicity among the rodents has not changed even after repetead treatments of the local patients. Based on our experiments, we conclude that N. squamipes has become a natural host of S. mansoni and possibly may participate in keeping the cycle of schistosomiasis transmission at Pamparräo Valley

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