Natural infection of wild rodents by Schistosoma mansoni parasitological aspects

Abstract

The evaluation of the role of rodents as natural hosts of Schistosoma mansoni was studied at the Pamparrão 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 Pamparrão Valley

A comparative parasitologic study on Biomphalaria glabrata snail and C3H/He mice infected with human and murine isolates of Schistosoma mansoni derived from Sumidouro, Rio de Janeiro, Brazil

“…Although no statistically significant, sex-ratio was male biased, as previously reported in either naturally infected N. squamipes trapped in Sumidouro (Silva et al 1992) or C3H mice infected with isolates derived from Vale do Rio Paraíba do Sul, São Paulo, Brasil) (Bastos et al 1979). The normal adult worm sex-ratio in Brazil is male biased (Souza et al 1996).…”

“…Considerable information acquired from earlier studies carried out at Sumidouro (state of Rio de Janeiro) showed that in a same transmission area, either humans or rodents harbor schistosomiasis mansoni infection (Silva et al 1992). Recently, it was demonstrated that cercariae deriving from sympatric murine and human isolates display only slight differences (Freire et al 2002).…”

Schistosome Satellite DNA Encodes Active Hammerhead Ribozymes

“…These two species also coparasitize their human hosts in Africa. In a locality of Bahia, Brazil, 47% of wild rodents are infected with S. mansoni (36), a favorable situation for interspecies crosses between S. mansoni and rodent schistosomes like Schistosomatium douthitti.…”

Biochemical and histological changes in liver ofNectomys squamipes naturally infected bySchistosoma mansoni

“…Schistosoma mansoni has been found in many endemic areas in Brazil naturally infecting wild animals (MODENA et al, 2008;MALDONADO et al, 2006). Nectomys squamipes, which is the main non-human definitive host of S. mansoni in Brazil (D'ANDREA et al, 2000), is characterized by its semi-aquatic habits and wide geographic distribution (BONVICINO et al, 2008;MALDONADO et al, 1994;RODRIGUES-SILVA et al, 1992;REY, 1993). Therefore, the occurrence of this semi-aquatic rodent in endemic areas is a factor that makes it difficult to control this zoonosis (SOUZA et al, 1992;D'ANDREA et al, 2000;GENTILE et al, 2006).…”