RESUMO
The presence of naturally portacaval shunts has been investigated in the vasculature of normal and Schistosoma mansoni-infected Rattus rattus. Using the technique of injecting Polystyrene microspheres in the superior mesenteric vein, we demonstrated that the presence of adult schistosomes in the lungs of R. rattus was not due to an innate anomaly of the rat vasculature but resulted from the formation of portacaval shunts during infection. In rats harbouring a bisexual infection, microspheres were only detected in the lungs from week 7. The development and increasing size of the shunts were maximal between weeks 7 and 10 and coincident with the translocation of adult worms from the portal tract to the lungs. At weeks 20-25, only 1-2% of the microspheres were recovered from the lungs, suggesting that the portacaval anastomoses have regressed due to reduction in portal hypertension after worm translocation. R. rattus with a male-only schistosome infection harboured adult worms in the lungs, indicating that the development of shunts does not solely depend upon egg deposition in the liver to generate hypertension. The relationships between the presence of the schistosomes in the lungs, the portacaval shunting and the resistance to reinfection is discussed.
Assuntos
Pulmão/parasitologia , Muridae/parasitologia , Veia Porta/fisiopatologia , Schistosoma mansoni/fisiologia , Animais , Feminino , Guadalupe , Hemodinâmica , Hipertensão Portal/parasitologia , Hipertensão Portal/fisiopatologia , Fígado/parasitologia , Pulmão/fisiologia , Masculino , Microesferas , Muridae/fisiologia , Contagem de Ovos de Parasitas , Perfusão , Veia Porta/parasitologia , Ratos , Fatores de TempoRESUMO
A comparative study of hourly cercarial productivities of Schistosoma mansoni from infected Biomphalaria glabrata was carried out in the presence of either healthy B. glabrata (control) or healthy Marisa cornuarietis (experimental). The results showed that, with M. cornuarietis, almost all the hourly cercarial productivities increased by a factor varying from 1.3 to 2.5 without modification of the shedding period.
Assuntos
Biomphalaria/parasitologia , Moluscos/fisiologia , Schistosoma mansoni/fisiologia , Animais , PeriodicidadeRESUMO
It was determined that M. cornuarietis, a mollusk which has been used as agent for the biological control of the schistosomiasis hosts, may be a plague for rice fields. Each mollusk can consume 0.3 g of this plant in 24 hours, accounting for the destruction of 0.015 m2 of a rice field. On the other hand, it was observed that B. glabrata shows preference for the consumption of M. cornuarietis faeces. This fact favors the vector's growth and reproduction rate and at the same time decreases its mortality.