Mem Inst Oswaldo Cruz, Rio de Janeiro, 99 (Suppl.I) August 2004
Freshwater Snails and Schistosomiasis Mansoni in the State of Rio de Janeiro, Brazil: V - Norte Fluminense Mesoregion
Departamento de Malacologia, Instituto Oswaldo Cruz-Fiocruz, Av. Brasil 4365, 21045-900 Rio de Janeiro, RJ, Brasil
In this paper, the fifth 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 Norte Fluminense Mesoregion from 2002 to 2003 are presented and revealed the occurrence of 19 species:u00a0Antillorbis nordestensis;u00a0Burnupiau00a0sp.;u00a0Biomphalaria tenagophila; Drepanotrema anatinum;u00a0Drepanotrema cimex; Drepanotrema depressissimum;u00a0Drepanotrema lucidum;u00a0Ferrissiasp.;u00a0Gundlachia ticaga;u00a0Gundlachiau00a0sp.;u00a0Heleobiau00a0sp.;u00a0Hebetancylus moricandi;u00a0Idiopyrgusu00a0sp.;u00a0Lymnaea columella;u00a0Melanoides tuberculatus; Physa acuta; Physa marmorata;u00a0Pomacea sordida, andu00a0Pomacea sp. Concerning the snail hosts ofu00a0Schistosoma mansoni onlyB.u00a0tenagophilau00a0was found, in contrast with other previuosly studied mesoregions. No specimens were found harbouring larval forms ofu00a0S.u00a0mansoniu00a0although different kinds of cercariae had been observed. An account about the current schistosomiasis transmission sites in this Mesoregion is presented as well.
An intensive and detailed survey of freshwater snails of the state of Rio de Janeiro has been performed by the authors since 1997 and the results were published in five papers (Thiengo et al. 1998, 2001, 2002ab, 2004). Thus, aiming to carry on that survey collections were made from March, 2002 to September, 2003 in the following municipalities of the Norte Fluminense Mesoregion: Carapebus, Conceição de Macabu, Macaé, Quissamã (Macaé Micro-region), Campos dos Goytacazes, Cardoso Moreira, São Fidélis, São Francisco de Itabapoana, and São João da Barra (Campos dos Goytacazes Microregion).
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 Afro-Asian snail Melanoides tuberculatus and 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 19 years are also presented.
MATERIALS AND METHODS
We have adopted the Brazilian Institute of Geography and Statistic (IBGE 1995) procedures in dividing the state of Rio de Janeiro into six Mesoregions (Baixadas, Metropolitan, Centro Fluminense, Sul Fluminense, Norte Fluminense, and Noroeste Fluminense) and the Center of Information and Data of Rio de Janeiro (CIDE 2001) for the new municipalities. The Norte Fluminense Mesoregion is 9731 km2, constituting 22.2% of the state.
The molluscs were collected from different suitable snail habitats from all 38 districts of the nine municipalities surveyed. Since at least three different habitats were investigated in each of the districts, an average of 114 samples was 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 on fresh lettuce leaves. In the meantime all specimens were exposed to artificial light at five-day intervals to determine possible infection with trematode larvae. Cercariae were fixed in 70% ethanol, stained with chloridric carmine, mounted in Canada balsam and subsequently identified according to Schell (1970).
The 10 larger specimens of each sample were preserved in Railliet-Henry's fluid after relaxation in a 0.05% hypnol solution and two of them were dissected under stereomicroscope for identification.
Samples of taxonomic importance were deposited at the Malacological Collection of Instituto Oswaldo Cruz.
The cases of schistosomiasis reported from 1985 to the first trimester of 2004 were obtained from the National Health Foundation (Funasa).
Table I shows the localities where the 19 molluscan species were found: Antillorbis nordestensis (Lucena, 1954);Biomphalaria tenagophila (Orbigny, 1835); Burnupia sp.; Drepanotrema anatinum (Orbigny, 1835);Drepanotrema cimex (Moricand, 1839); Drepanotrema depressissimum (Moricand, 1839); Drepanotrema lucidum (Pfeiffer, 1839); Ferrissia sp.; Gundlachia ticaga (Marcus & Marcus, 1962); Gundlachia sp.;Hebetancylus moricandi (Orbigny, 1837); Heleobia sp.; Idiopyrgus sp.; Lymnaea columella Say, 1817;Melanoides tuberculatus (Müller, 1774); Physa acuta Draparnaud, 1805; Physa marmorata Guilding, 1828;Pomacea sp., and Pomacea sordida (Swainson, 1823).
The distribution of B. tenagophila, L. columella, the main intermediate host of Fasciola hepatica (Linné) in Brazil, as well as that of the introduced species M. tuberculatus is shown in the Figure.
The highest species richness occurred in Campos (17 species), São Fidélis (14), and Macaé (13). On the other hand, in Carapebus and Quissamã only seven species were found.
Specimens of P. marmorata were found in all municipalities, but Quissamã whereas those of P. acuta were found in Campos dos Goytacazes Microregion only.
In contrast to the other previously studied Mesoregions (Thiengo et al. 2001, 2002a b, 2004) B. tenagophila was the only schistosomiasis vector found and the most frequent species, as it was observed in 34 districts.
Although many different kinds of cercariae had been observed (Table II), no specimens were found infected withS. mansoni or F. hepatica. Xiphidiocercariae group (including Ubiquita cercaria and Ornatae cercaria) were the most frequent type of trematode larvae, as they occurred in the following species: B. tenagophila, D. cimex, D. depressissimum, D. lucidum, G. ticaga, L. columella, P. sordida, and Pomacea sp. The major diversity of cercariae was found in Campos and B. tenagophila showed the greatest number of mollusc-parasite interactions, followed by D. cimex and Pomacea sp.
Even though no specific parasitological surveys have been performed by Funasa in the Norte Fluminense Mesoregion, cases of schistosomiasis were detected in Macaé (one in 2000; 21 in 2001; 19 in 2002; nine in 2003; and five in 2004), Conceição de Macabu (14 in 1993; one in 1996 and 2000) and Campos dos Goytacazes (nine in 1989 and two in 1993).
The present study extended the geographical distribution of B. tenagophila in the state of Rio de Janeiro (Paraense 1986, Thiengo et al. 1998, 2001, 2002a b, 2004). It was previously recorded in Metropolitana Mesoregion (all municipalities), Centro Fluminense Mesoregions (all municipalities), Baixadas Mesoregion (all municipalities except Arraial do Cabo), Sul Fluminense Mesoregion (all municipalities except Parati), and Norte Fluminense Mesoregion (Campos dos Goytacazes and Macaé), including 69 municipalities in the state. The records for Carapebus, Conceição de Macabu, Quissamã, São João da Barra, São Francisco de Itabapoana, São Fidélis, and Cardoso Moreira are new.
In relation to the non-vector planorbid species, D. anatinum was the most common, followed by D. cimex. In the previously studied mesoregions, the most frequent species were D. anatinum in the Metropolitana and Centro Fluminense Mesoregions (Thiengo et al. 2001, 2002a), D. cimex in the Baixadas Mesoregion (Thiengo et al.2002b) and D. lucidum in the Sul Fluminense Mesoregion (Thiengo et al. 2004). The distribution ofA. nordestensis, previously known in 28 municipalities in the state (Thiengo et al. 1998, Santos et al. 1999, Thiengo et al. 2001, 2002ab, 2004), is now extended to include Campos, Conceição de Macabu, Macaé, and São Fidélis.
Lymnaea columella shows wide range in the state and, in Norte Fluminense Mesoregion specimens were collected from five municipalities and 16 districts.
Of the remaining Pulmonata species, P. marmorata was found most frequently (8 municipalities; 27 districts) similarly to Baixadas, Centro and Sul Fluminense Mesoregions (Thiengo et al. 2002a b, 2004).
The Afro-Asian thiarid M. tuberculatus was found in four municipalities and seven districts in the northern Norte Fluminense Mesoregion. The current distribution of that invasive gastropod competitor of planorbid intermediate hosts of S. mansoni in Brazil had already been reported by our group (Fernandez et al. 2003). The first record of that species in the country was in 1967 in Santos, state of São Paulo, and since then it has been recorded in the Distrito Federal and 17 out of the 26 states from Brazil.
Concerning the other Prosobranchia, hydrobiid species were found in the all municipalities, but Conceição de Macabu and Quissamã. Heleobia sp. was the most frequent species of Hydrobiidae, and Idiopyrgus sp. was found only in Campos. As in Mesoregion Baixadas the geographical distribution of hydrobiid species is probably due to favorable environmental conditions such as the occurrence of many brackish waterbodies, where most specimens were collected.
Specimens of Pomacea sp., collected from eight municipalities, are quite different from those reported by Thiengo et al. (2002ab, 2004) in Centro Fluminense, Baixadas and Sul Fluminense Mesoregions. Further morphological and molecular studies are being undertaken on samples from those regions, in order to identify them.
Among the ancylids G. ticaga occurred in six municipalities and was the most frequently found species as well as the previously studied mesoregions. Of the remaining ancylid species, H. moricandi was reported in the Metropolitana Mesoregion only (Thiengo et al. 1998), under the name of Gundlachia moricandi (Orbigny, 1837); specimens of Burnupia sp. were found in the Baixadas and Metropolitana Mesoregions whereas those of Fer-rissia sp. in all previously studied Mesoregions.
Due to the limitation of logistic resources available to Funasa no intensive parasitological surveys have been done during the last years. Thus the number of positive cases in the period studied (82 in three municipalities) must be seen as underestimated information.
With regard to other trematode, the xiphidiocercariae group was the most frequently larval type found in the molluscs, corroborating Thiengo et al. (2002a b, 2004).
To Dr Patricia Moza (Funasa, RJ) for informing the number of cases of schistosomiasis in the state.
CIDE-Centro de Informações e Dados do Rio de Janeiro 2001. Secretaria do Estado de Planejamento, Desenvolvimento Econômico e Turismo, Rio de Janeiro: map.
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