Mem Inst Oswaldo Cruz, Rio de Janeiro, 96 (Suppl.I) September 2001
Freshwater Snails and Schistosomiasis Mansoni in the State of Rio de Janeiro, Brazil: I - Metropolitan Mesoregion
Departamento de Malacologia, Instituto Oswaldo Cruz-Fiocruz, Av. Brasil 4365, 21045-900 Rio de Janeiro, RJ, Brasil
IDepartamento de Ciências Biológicas, Escola Nacional de Saúde Pública-Fiocruz, Rio de Janeiro, RJ, Brasil
IISecretaria Estadual de Saúde, Rio de Janeiro, RJ, Brasil
IIIInstituto de Biologia Roberto Alcântara Gomes, Laboratório de Malacologia, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, Brasil
In order to elaborate a planorbid chart of the State of Rio de Janeiro a survey of freshwater gastropods in the Metropolitan Mesoregion of this State was performed and revealed the occurrence of 20 species:u00a0Antillorbis nordestensisu00a0(Lucena, 1954);u00a0Biomphalaria glabratau00a0(Say, 1818);u00a0Biomphalaria schrammiu00a0(Crosse, 1864);u00a0Biomphalaria stramineau00a0(Dunker, 1848);u00a0Biomphalaria tenagophilau00a0(Orbigny, 1835);u00a0Burnupiau00a0sp.;u00a0Drepanotrema anatinumu00a0(Orbigny, 1835);u00a0Drepanotrema cimexu00a0(Moricand, 1839);u00a0Drepanotrema lucidumu00a0(Pfeiffer, 1839);u00a0Ferrissiau00a0sp.;u00a0Gundlachia ticagau00a0(Marcus & Marcus, 1962);u00a0Heleobia davisiu00a0Silva & Thomé, 1985;u00a0Lymnaea columellau00a0Say, 1817;u00a0Melanoides tuberculatusu00a0(Müller, 1774);u00a0Physa cubensisu00a0Pfeiffer, 1839;u00a0Physa marmoratau00a0Guilding, 1828;u00a0Pomacea sp.; Pomacea canaliculatau00a0(Lamarck, 1822);u00a0Pomacea lineatau00a0(Spix, 1827) andu00a0Pomacea sordidau00a0(Swainson, 1823). Among the planorbid speciesu00a0B. tenagophilau00a0was the most frequent, occurring in all municipalities surveyed. The present study extends the distribution ofu00a0B.u00a0stramineau00a0in the State of Rio de Janeiro and reports new records foru00a0A.u00a0nordestensis,u00a0B.u00a0schrammi,u00a0G.u00a0ticaga,u00a0H.u00a0davisiu00a0and the generau00a0Burnupiau00a0andu00a0Ferrissia.u00a0An account about the current transmission areas of schistosomiasis mansoni in this Mesoregion is presented as well.
Papers concerning surveys of freshwater snails in Brazil are still scarce in spite of the diversity of species and the importance of some of them to Public Health: Luz et al. (1998), Morretes (1949), Paraense (1983), Paraense et al. (1983), Vaz et al. (1987), Souza et al. (1998) and Thiengo et al. (1998).
In order to elaborate a chart of planorbids of the State of Rio de Janeiro, collecting was done during the last three years in the following municipalities of the Metropolitan Mesoregion of the State: Engenheiro Paulo de Frontin, Mendes, Miguel Pereira, Paracambi, Paty do Alferes and Vassouras (Microregion Vassouras); Cachoeiras de Macacu and Rio Bonito (Microregion Macacu-Caceribu); Itaguaí and Mangaratiba (Microregion Itaguaí); Belford Roxo, Duque de Caxias, Itaboraí, Japeri, Maricá, Nilópolis, Niterói, Nova Iguaçu, Queimados, Rio de Janeiro, São Gonçalo and São João de Meriti (Microregion Rio de Janeiro).
Data concerning Petrópolis, São José do Vale do Rio Preto and Teresópolis (Microregion Serrana) and the municipalities of Magé and Guapimirim (Microregion Rio de Janeiro) were previously published elsewhere (Thiengo et al.1998).
A list of freshwater snail species of the above mentioned area is presented, based on material collected by the authors and on the collection of the Department of Malacology of Instituto Oswaldo Cruz (CMIOC). An account about the transmission areas of schistosomiasis mansoni in this Mesoregion, a map showing the distribution of the species of medical and veterinary importance and a survey of the different kinds of cercariae found are presented as well.
MATERIALS AND METHODS
We follow the Brazilian Institute of Geography and Statistic (IBGE 1995) which divides politically and administratively the State of Rio de Janeiro into 81 municipalities arranged in 6 mesoregions and 18 microregions.
The molluscs were collected from different suitable snail habitats (streams, rivers, marsh areas, drainage and sewage ditches, ponds, flood areas and irrigation canals) in all 61 districts of the 22 municipalities in the surveyed area. Since three different habitats were investigated in each of the districts, an average of 183 samples were obtained.
Live snails were kept at the laboratory for a month in aquaria containing dechlorinated tap water and, at the bottom, a thin layer of a 2:1 mixture of screened soil and ground oyster shells as a source of mineral nutrients. Snails were fed fresh lettuce leaves. In the meantime, all specimens were exposed to artificial light in intervals of five days to determine possible infection with trematode larvae. The cercariae were fixed in 70% ethanol, stained with chloridric carmine and mounted in Canada balsam, using Shell (1970) for identification.
The ten larger specimens of each sample were preserved in Railliet-Henry's fluid after relaxation in a 0.05% nembutal solution and two of them were dissected under a stereomicroscope for identification.
Samples of taxonomic importance were deposited at the Malacological and Helminthological Collections of Instituto Oswaldo Cruz.
Parasitological stool surveys, employing the Kato-Katz method (Katz et al. 1972), were carried out in three localities of Rio de Janeiro City, in collaboration with National Health Foundation (Funasa).
The results of the parasitological survey from 1996 to the first trimester of 2000 were obtained in consolidated returns from Funasa, excluding Rio de Janeiro City where the positive cases from 1996 to 1998 were obtained from the Co-ordination of Epidemiology Programme of Health Secretary of Rio de Janeiro City.
The Table I comprises the localities where the species have been found in the surveyed area. The distributionof the three vectors of Schistosoma mansoni Sambon, 1907 and Lymnaea columella Say, 1817 is showed in the Figure.
In all, 8 species of planorbids and 12 other freshwater gastropods were found: Antillorbis nordestensis (Lucena, 1954);Biomphalaria glabrata (Say, 1818); Biomphalaria schrammi (Crosse, 1864); Biomphalaria straminea (Dunker, 1848); Biomphalaria tenagophila (Orbigny, 1835); Burnupia sp.; Drepanotrema anatinum (Orbigny, 1835); Drepanotrema cimex(Moricand, 1839); Drepanotrema lucidum (Pfeiffer, 1839); Ferrissia sp.; Gundlachia ticaga (Marcus & Marcus, 1962);Heleobia davisi Silva & Thomé, 1985; L. columella; Melanoides tuberculatus (Müller, 1774); Physa cubensis Pfeiffer, 1839; Physa marmorata Guilding, 1828; Pomacea sp.; Pomacea canaliculata (Lamarck, 1822); Pomacea lineata (Spix, 1827) and Pomacea sordida (Swainson, 1823). The greatest variety of species was observed in the municipality of Maricá and Rio de Janeiro City.
Although different kinds of cercariae had been observed, no specimens were found infected with S. mansoni, as shown in the Table II. The major diversity of cercariae were found in B. tenagophila which was also the most parasited species. The Xiphidiocercariae group was the most frequent and it was found in all species of parasited molluscs, except forG. ticaga and M. tuberculatus. This latter presented only Pleurolophocercus cercariae, which has not yet been reported in Brazil.
The results of the parasitological survey from 1996 to the first trimester of 2000 are shown in Table III. In Rio de Janeiro City, the parasitological survey was performed in three localities recognised as potential transmission sites. In the locality of Santa Cruz, where stool examination began in 1996, 12 positive cases were found in that year, 8 in 1997, 4 in 1998, 15 in 1999 and 0 in 2000. Vargem Grande was the second locality studied and, 33 positive cases were detected in 1998, 44 in 1999 and 1 in 2000. In the locality of Alto da Boa Vista 36 were recorded in 1999 and 16 in 2000.
Concerning the snail host distribution in Alto da Boa Vista and Vargem Grande localities, only B. tenagophila was collected.
The most frequent species was B. tenagophila, occurring in all the localities surveyed. The occurrence of two natural vectors of S. mansoni, B. tenagophila and B. straminea, was observed in Duque de Caxias, Itaboraí, Mangaratiba, Maricá, Miguel Pereira, Niterói, Nova Iguaçu, Paracambi, Rio de Janeiro, São Gonçalo and Vassouras. Sintopy involving these species was observed only in Niterói. Magalhães (1964) reported the coexistence of B. tenagophila and B. glabratain Manguinhos, on the Campus of Instituto Oswaldo Cruz. The same was observed by Grault et al. (1998) in three breeding sites in Santa Cruz, a locality in the west area of Rio de Janeiro City. We did not find B. glabrata in Santa Cruz, even after exhaustive sampling in the areas pointed out. The authors reported that the appearance of B. glabrata inB. tenagophila natural breeding sites occurred after a period of heavy rains, probably as a result of accidental introduction of B. glabrata into artificial ponds in Serra da Paciência hill range. Nowadays, although B. glabrata still occurs in three different breeding sites on the Campus of Fundação Oswaldo Cruz, it is not found in sintopy withB. tenagophila.
The distribution of B. straminea in the State, previously known to Duque de Caxias, Guapimirim, Magé, Paracambi and Petrópolis (Paraense 1986, Thiengo et al.1998) was now extended to 14 municipalities, as shown in the Figure. Concerning Paracambi, according to Silva et al. (1997) and the present investigation, only B. tenagophila occurs in that municipality nowadays. The possibility of disappearance of B. straminea as a result of competition with B. tenagophila is considered by the authors.
During this investigation we failed to find molluscs in Nilópolis probably due to environmental changes resulting from urbanism and the heavy pollution of the few waterbodies available. The record of B. tenagophila in Nilópolis was obtained from the collection (CMIOC 3009), sample collected in 1984. Similarly, B. schrammi from Nova Iguaçu was also obtained from the collection (CMIOC 82, from 1954), once this species was not found in this investigation.
The present study extended the geographical distribution of A. nordestensis and B. schrammi (Table I). So far onlyA. nordestensis was reported in two municipalities (Guapimirim and Petrópolis) of the State of Rio de Janeiro (Thiengo et al. 1998).
Concerning the non-planorbid gastropods, P. cubensis, P. marmorata and L. columella were the most frequent species in the surveyed area.
In relation to the Ancylidae, G. ticaga was the most common species, occurring in limpid as well as in polluted habitats. Along with Burnupia sp., it has been recorded for the first time in Rio de Janeiro. Previous reports in the country ofBurnupia sp. were Espírito Santo, Alagoas, Rio Grande do Sul and Santa Catarina (Santos 1990, Lanzer 1991); and forFerrissia sp., Rio de Janeiro, Rio Grande do Sul, Santa Catarina, Espírito Santo and Alagoas (Santos 1990, Lanzer 1991, Thiengo et al. 1998).
The asiatic thiarid M. tuberculatus was found in 14 out of the 22 municipalities, generally in areas with dense populations inhabiting lotic, lentic, polluted or limpid waterbodies. The most frequent ampullariid, P. sordida, originally described to São Cristovão, a neighborhood located in downtown Rio de Janeiro, seems to be more vulnerable to environmental changes resulted from urbanism, once itwas collected only from limpid habitats in the peripheries of the municipalities. On the contrary, P. canaliculata inhabited even polluted breeding sites in urban areas. The only record of P. lineata was on the Campus of Fundação Oswaldo Cruz. The records of H. davisi here presented are the most northern distribution of this species, reported previously to the south of the country.
This paper reports M. tuberculatus, A. nor-destensis and G. ticaga acting as intermediate hosts of trematodes in Brazil for the first time.
With regard to schistosomiasis, because of the limitation of logistic resources available to Funasa in the last ten years, the numbers of positive cases must be seen as underestimated information. The results of the coproscopical survey in Rio de Janeiro also indicate that appreciable transmission is continuing in the localities of Alto da Boa Vista and Vargem Grande, since both localities have been recognised as low transmission sites (Suassuna & Coura 1969). In contrast with the latter two localities, Santa Cruz transmission has been reducing after intervention carried out by the local health authorities.
To the Regional Directory of National Health Foundation of Rio de Janeiro (Funasa/RJ) in 1984, for sending us samples of snails from several localities of the State and to Dr WL Paraense, Head of Laboratory of Malacology, IOC-Fiocruz for the facilities supplied throughout this investigation.
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