Identificação de populações de Biomphalaria (Gastropoda:Planorbidae) na região sul do Rio Grande do Sul, Brasil

Abstract

Mansonic schistosomiasis is a disease related to the presence of the snail, belonging to the genus Biomphalaria (Preston, 1910), which presents aquatic habit susceptible to the Schistosoma mansoni (Sambon, 1907). The knowledge about the geographic distribution of the Biomphalaria species is important to the control and epidemiological monitoring of the schistosomiasis. The expansion of this parasitosis to the Southern region of Brazil was evidenced by the occurrence of the vector snail, especially B. glabrata (Say, 1818), the presence of the host of this trematod, as well as the environmental conditions which provide the settings to the development of the complete biological cycle. The aim of this work was characterize Biomphalaria species in the Southern of Rio Grande do Sul state, Brazil. The snails were collected during the year 2005, from 15 places of 12 municipalities of the state, these populations were maintained in laboratory conditions and the habitat characteristics analyzed. The morphological identification of the snails was realized trough the shelves characteristics, renal rid and reproductive organs anatomy. To complement this analyzes a molecular identification was carried out trough the PCR-RFLP with amplification of the ITS regions, which includes the gene of subunit 5.8S of the rDNA and the transcriptions spaces ITS1 and ITS2. The susceptibility of two populations potentially vectors were tested using the LE strain. Seven populations of B. tenagophila guaibensis (Paraense, 1984), five of B. peregrine (Orbigny, 1835) and three of B. oligoza (Paraense, 1975) were identified in the morphological and molecular diagnosis. Amongst the populations maintained in laboratory, four populations of B. tenagophila guaibensis and all populations of B. peregrina reproduced in these conditions, producing the F1 generation. Two populations of B. peregrina (from Dom Pedrito and Rio Grande counties) were experimentally infected and showing resistance to the infection by S. mansoni. The specific diagnosis performed by molecular techniques presents more efficiency when compared to the morphological diagnosis, became an important tool in epidemiological studies of this snail. The continuing of the malacology 12 and epidemiological research in different populations of Biomphalaria spp., which represents all the state is necessary, the knowledge of the characteristics of these populations permit to trace strategies to avoid the establishment and expansion of the schistosomiasis in Rio Grande do Sul state.