Holochilus brasiliensis and nectomys squamipes (Rodentia-Cricetidae) natural hosts of Schistosoma mansoni

Abstract

After several Brazilian researchers, the author examines the capacity of two species of rodents Cricetidae, Holochilus brasiliensis and Nectomys squamipes, to maintain the biological cycle of Schistosoma mansoni in the field and to be parasite reservoir: (a) the role they are able to play in human endemy; (b) the methods necessary to characterize the population of Schistosoma mansoni related either to man, either to rodents, either to both.

The Role of Wild Rodents in the Transmission of Schistosoma mansoni in Brazil

“…Veiga-Borgeaud et al (1986) found a high prevalence of S. mansoni in H. brasiliensis (currently H. sciureus) in swampy areas in Maranhão State. Picot (1992) confirmed the ability of the rodents N. squamipes and H. brasiliensis to eliminate viable eggs in feces in natural conditions. Some other studies carried out in Africa and other countries of the Americas also investigated the importance of mammals as S. mansoni reservoirs.…”

“…Ribeiro et al (1998) and Souza et al (1992) showed that N. squamipes presented with a high rate of recovered worms even when infected with a low number of cercariaes, suggesting compatibility between N. squamipes and S. mansoni. Picot (1992) showed that in semi-natural conditions, N. squamipes was able to close the transmission cycle of S. mansoni and to eliminate highly infectious, viable eggs. Maldonado Jr. et al (1994) evaluated the resistance of S. mansoni infection in N. squamipes by successive experimental infections, comparing the total number of worms recovered from re-infections with a control group.…”

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

“…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 .…”

An ecological field study of the water-rat Nectomys squamipes as a wild reservoir indicator of Schistosoma mansoni transmission in an endemic area

“…Among the extra-human definitive hosts of this parasite, rodents of the genera Nectomys and Holochilus are the most probable wild reservoirs taking into account: (1) their semiaquatic habits (Ernest & Mares 1986), which make them highly exposed to infection; (2) their wide geographic distribution (Bonvicino 1994) coincident with the distribution of schistosomiasis in Brazil; (3) presence of infected individuals in most of the endemic areas where they were investigated, despite of the low human prevalence -rodents frequently showing higher infection rates in relation to human populations (Rey 1993); (4) rodent tolerance to human presence, occurring near human dwellings. Several experimental studies also support the hypothesis that water-rats are probable wild reservoirs of S. mansoni, showing high susceptibility to infection (Borda 1972, Souza et al 1992, Maldonado Jr. et al 1994, Ribeiro et al 1998, somatic development hypertrophy of adult worms , elimination of viable eggs with high infectivity potential (Picot 1992), high infection persistence , low pathogenicity with efficient peri-ovular modulation and low tissue aggression (Silva & Andrade 1989), and ability to close the transmission cycle in semi-natural conditions (Antunes et al 1973, Carvalho et al 1976, Kawazoe & Pinto 1983. Infection of small mammals other than Nectomys and Holochilus by S. mansoni occurs only occasionally, especially in areas of high transmission levels.…”