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

Abstract

The aim of the present research was to evaluate the potential of Nectomys rattus, the "water rat", to develop Schistosoma mansoni infection. Comparison Key words: Nectomys rattus -Nectomys squamipes -wild rodent -Schistosoma mansoni -experimental infectionThe occurrence of wild populations of small rodent naturally infected in endemic schistosomiasis areas had been considered as an additional complication factor for the control of the disease (Rey 1993).The species Nectomys squamipes, the "water rat", is one of the most important non-human hosts for Schistosoma mansoni in Brazil (Antunes et al. 1973, Picot 1992. This species excretes viable eggs of the parasite during its hole life-span (RodriguesSilva 1988) and shows strong fitness to parasitism . Furthermore, N. squamipes has a high susceptibility to experimental infection (Souza et al. 1992), reinfection (Maldonado Jr. et al. 1994), and with a moderate pathogenic response (Silva & Andrade 1989 at the eastern Brazilian coast, from north of the municipality of São Lourenço da Mata (State of Pernambuco) to the Amazon river. That new given designation is N. rattus (2n=52).N. squamipes (2n=56) distribution has been restricted to the Atlantic coast of Brazil, in the basins of São Francisco river and Paraná river, as well as in the small independent basins of southern São Lourenço da Mata, in eastern Brazil.The broad distribution of N. rattus includes endemic areas of schistosomiasis apart from those where N. squamipes are found. However, there have been only two reports where N. rattus (formerly named N. squamipes amazonicus) were found naturally infected (Bastos et al. 1982(Bastos et al. , 1984.The aim of this research was to evaluate the potential of N. rattus to develop S. mansoni infection, and its ability to complete the parasite's life cycle under experimental conditions. All results were compared to the N. squamipes relation with S. mansoni infection. MATERIALS AND METHODSExperimental groups -Thirty seven specimens of N. rattus and 58 specimens of N. squamipes of both sexes, aged 3 to 5 months and weighing 250 to 300 g were used. All experimental animals were raised in our laboratory colonies (D'Andrea et al. 1996). The colony of the N. rattus derived from animals captured in the State of Goiás

Biological implications of the phenotypic plasticity in the Schistosoma mansoni - Nectomys squamipes model

“…In this study, overall results confirm that N. squamipes is a permissive host to S. mansoni 17,18,20,32,33,34 . It must be also emphasized that S. mansoni adult worms might detect signals from their environment and responding appropriately in a state-dependent manner could greatly enhance its fitness 36 .…”

Genetic differentiation in geographically close populations of the water rat Nectomys squamipes (Rodentia, Sigmodontinae) from the Brazilian Atlantic Forest

“…This significant population differentiation indicates that migration is probably restricted (resulting in limited gene flow), this view being supported by ecological studies showing that N. squamipes dispersion is restricted and that most movement is confined to riverbanks. This finding is relevant in view of the fact that N. squamipes is a reservoir of S. mansoni (Ernest and Mares, 1986) and that its extensive distribution covers most areas where schistosomiasis is endemic (Ribeiro et al, 1998) and where some rodent populations show infection rates higher than 90% (Veiga-Borgeaud et al, 1986, 1987. One of the authors (L.S.…”

Natural Schistosoma mansoni infection in Nectomys squamipes: histopathological and morphometric analysis in comparison to experimentally infected N. squamipes and C3H/He mice

“…Laboratory studies have demonstrated that N. squamipes is highly susceptible to experimental S. mansoni infection (Rodrigues-Silva 1988, Souza et al 1992, Maldonado Jr. et al 1994, Ribeiro et al 1998. It presents a well-balanced relationship with the parasite, since life-long infections do not affect its life span (RodriguesSilva et al 1992) or its reproductive capacity (D'Andrea et al 2000), therefore being considered a permissive host (Machado-Silva et al 1997).…”