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Mem. Inst. Oswaldo Cruz vol.97 suppl.1 Rio de Janeiro Oct. 2002
Freshwater Snails and Schistosomiasis Mansoni in the State of Rio de Janeiro, Brazil: III - Baixadas Mesoregion
Vol. 97(Suppl. I): 43-46, 2002
Silvana C Thiengo/+, Monica A Fernandez, M Fernanda Boaventura, Marcos G Magalhães, Sonia B Santos*
Departamento de Malacologia, Instituto Oswaldo Cruz-Fiocruz, Av. Brasil 4365, 21045-900 Rio de Janeiro, RJ, Brasil *Laboratório de Malacologia, Instituto de Biologia, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, Brasil
In this paper, the third of a series dealing with the survey of freshwater gastropods of the state of Rio de Janeiro, the results of collections carried out in the Mesoregion Baixadas from 2000 to 2002 are presented. Twenty-two species, belonging to seven families, were found. As to the snail intermediate hosts of Schistosoma mansoni, the most frequent species was Biomphalaria tenagophila besides some new findings of Biomphalaria straminea. No specimens were found harboring larval forms of S. mansoni although different kinds of cercariae had been observed.
Key words: schistosomiasis mansoni - freshwater snails - cercariae - Rio de Janeiro - Brazil
Aiming to elaborate a chart of planorbids of the state of Rio de Janeiro, collections have been done by the authors since 1997. During the last two years, from March 2000 to May 2002, collecting was done in the following municipalities of the Baixadas Mesoregion: Casimiro de Abreu, Rio das Ostras and Silva Jardim (Microregion Bacia de São João); Araruama, Armação dos Búzios, Arraial do Cabo, Cabo Frio, Iguaba Grande, São Pedro da Aldeia and Saquarema (Microregion Lagos). This Mesoregion has nowadays 14 Units of Nature Conservation including Biological Reserves and Areas of Environmental Protection. Once seven out of the ten municipalities are located at the littoral, there are plenty of brackish waterbodies.
The freshwater snail species listed include specimens collected by the authors as well as those in the Collection of the Department of Malacology of Instituto Oswaldo Cruz. The distribution of the snail species of medical and veterinary importance, various kinds of cercariae and the number of schistosomiasis cases reported to this region during the last seven years are also presented.
We have adopted the Brazilian Institute of Geography and Statistics (IBGE 1995) procedures in dividing the state of Rio de Janeiro into six Mesoregions and the Center of Information and Data of Rio de Janeiro (Cide 2001) for the new municipalities.
The molluscs were collected from different suitable snail habitats from all 24 districts of the ten municipalities. Since at least three different habitats were investigated in each of the districts, an average of 79 samples was obtained. Live snails were exposed to artificial light at five-day intervals to determine possible infection with trematode larvae. Cercariae were fixed in 70% ethanol, stained with chlorhydric carmine, mounted in Canada balsam and subsequently identified according to Schell (1970).
The ten largest specimens of each mollusc sample were preserved in Railliet-Henry's fluid after relaxation in a 0.05% nembutal solution. Two were dissected under a stereomicroscope for identification purpose.
Samples of taxonomic importance were deposited at the Malacological and Helminthological Collections of Instituto Oswaldo Cruz.
The cases of schistosomiasis reported from 1996 to the first trimester of 2002 were obtained from the National Health Foundation (Funasa).
Table I shows the localities where the 22 molluscan species were found: Antillorbis nordestensis (Lucena, 1954); Biomphalaria schrammi (Crosse, 1864); Biomphalaria straminea (Dunker, 1848); Biomphalaria tenagophila (d'Orbigny, 1835); Burnupia sp.; Drepanotrema anatinum (d'Orbigny, 1835); Drepano-trema cimex (Moricand, 1839); Drepanotrema lucidum (Pfeiffer, 1839); Ferrissia sp.; Gundlachia ticaga (Marcus & Marcus, 1962); Heleobia australis australis (d'Orbigny, 1835); Heleobia bertoniana (Pilsbry, 1911); Heleobia parchappei (d'Orbigny, 1835); Heleobia sp.; Idiopyrgus souleyetianus Pilsbry, 1911; Lymnaea columella Say, 1817; Melanoides tuberculatus (Müller, 1774); Physa cubensis Pfeiffer, 1839; Physa marmorata Guilding, 1828; Pomacea sp.; Pomacea canaliculata (Lamarck, 1822) and Pomacea sordida (Swainson, 1823).
The highest species richness occurred in Araruama (14 species), Rio das Ostras (13), and Silva Jardim (13). On the other hand, in Armação dos Búzios and Arraial do Cabo only three and two species were found, respectively.
Specimens of B. tenagophila and P. marmorata were found in all municipalities except Arraial do Cabo, where only hydrobiid specimens were collected.
Although many different kinds of cercariae had been observed (Table II), no specimens were found infected with Schistosoma mansoni Sambon, 1907 or Fasciola hepatica (Linné). Xiphidiocercariae were the most frequent type of trematode larvae.The major diversity of cercariae was found in Araruama, in the following species: A. nordestensis, B. tenagophila, D. cimex, L. columella and P. marmorata.
As in Mesoregion Baixadas no transmission sites for schistosomiasis had been reported, no specific parasitological surveys have been performed by Funasa. From 1996 to the first trimester of 2002 six cases of schistosomiasis were detected: Rio das Ostras (one in 2000; four in 2001) and São Pedro da Aldeia (one in 2001).
The present study extended the geographical distribution of B. tenagophila and B. straminea, natural vectors of schistosomiasis in Brazil. Biomphalaria straminea was previously recorded in 18 municipalities in the state of Rio de Janeiro (Paraense 1986, Thiengo et al. 1998, 2001, 2002) and the records for Casimiro de Abreu, Iguaba Grande and Silva Jardim are new. The distribution of those species as well as of L. columella, vector of fascioliasis, is shown in the Figure.
In relation to the non-vector planorbid species, D. cimex was the most common, followed by A. nordestensis. In the previously studied Mesoregions, e.g., Metropolitana (Thiengo et al. 2001) and Centro Fluminense (Thiengo et al. 2002) D. anatinum was the most frequent. The distribution of A. nordestensis, previously known in 18 municipalities in the state (Thiengo et al. 1998, 2001, 2002, Santos et al. 1999) is now extended to include Araruama, Cabo Frio, Casimiro de Abreu, Rio das Ostras, São Pedro da Aldeia, Saquarema and Silva Jardim.
Of the remaining pulmonate species, P. marmorata was found most frequently (9 districts), followed by L. columella (6 districts). In contrast to the wide distribution observed in the two other Mesoregions, P. cubensis was found only in Casimiro de Abreu.
The Afro-Asian thiarid M. tuberculatus was found only in Saquarema. On the contrary, it has a wide range in the Metropolitan perhaps owing to the major influence of anthropic action that has been taking place at that Mesoregion during the last years. The greatest number of hydrobiid species in that Mesoregion is probably due to favorable environmental conditions such as the occurrence of many brackish waterbodies, where most species were collected.
Concerning the ampullariids, P. sordida was the most frequent species. Pomacea sp. collected from Araruama is the same found in some municipalities of the Centro Fluminense Mesoregion. Further morphological studies are being undertaken on samples from both regions, to permit identification to species level.
Ferrissia, the most complex and probably the most widespread genus of Ancylidae, is now represented in Brazil only by Ferrissia gentilis Lanzer, 1991 from the South of the country. Ferrissia sp., collected in Casimiro de Abreu and Silva Jardim, is quite different from F. gentilis by morphological and conchological characters. The commonest ancylid species in the surveyed region is G. ticaga, also observed in the Metropolitan and Centro Fluminense Mesoregions.
Similarly to the above-mentioned Mesoregions, the xiphidiocercariae were the most frequently kind found in the molluscs. The trematode larval type, Pleurolo-phocercus cercaria, previously found only in M. tuberculatus in Brazil (Boaventura et al. 2002), was also found in the hydrobiids H. parchappei and I. souleyetianus.
To Luiz Carlos Pina (Funasa/RJ) for informing the number of cases of schistosomiasis, to Maria Cristina Pons da Silva for identification of the hydrobiid species and to Aline Carvalho de Mattos, for technical assistance.
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