Colonization of Pomacea haustrum (Reeve, 1856) at localility with Schistosomiasis mansoni: Baldim, MG (Brazil)

Abstract

In the region of Baldim, MG (Brazil) - a well-known Schistosoma mansoni endemic area where transmission control had already been unsuccessfully attempted through molluscicide, sanitary education and clinical treatment - 5,421 specimens of Pomacea haustrum (Prosobranchia, Pilidae) were introduced into 5 brooks and 2 ditches where Biomphalaria glabrata (primarily) and B. straminea (secondarily) predominated. From 1968 to 1971, the infection rate of B. glabrata by S. mansoni ranged from 2.1% to 11.9%. None of the B. straminea specimens collected, however, were seen to be liberating cercariae of this trematode. After the introduction of Pilidae, only once were two positive B. glabrata specimens (1.8%) detected. A decrease in the planorbide population was observed, as well as an increase in the pomacea density to 20.0 and 121.6 specimens per square meter in the brooks and ditches, respectively. P. haustrum density was estimated by the "quadrat" method. Of the planorbides in the experiment, 65.2% (1,526) were collected from July/68 to July/72 and the rest were obtained after the introduction of the predator-competitor species, as follows: 15.0% (352) in 1976; 16.1% (377) in 1977; and 3.7% (87) in 1978. Although transferred from a lenitic medium (Sete Lagoas, MG), the pomaceae became perfectly adapted to the lotic collections of Baldim, and proved to be capable of replacing the original B. glabrata populations of several biotopes or, at least, of becoming predominant, with no damage to the new ecosystems. Based on the data presented above and the knowledge previously acquired in the study of the biology and ecology of the species, it is believed that, under similar conditions, Pomacea haustrum (Reeve, 1856) - and, by extension, P. lineata (Spix, 1827) and P. canaliculata (Lamarck, 1822), as well as other species from the same genus - may be successfully used in the biological control of the intermediate hosts of S. mansoni.