Plant-derived molluscicides have been indicated as biodegradable and lowcost strategies for control of Biomphalaria spp., intermediate host for the Schistosoma. This study evaluated whether the crude ethanolic extract of the Persea americana stem bark has molluscicidal activity against embryos, newly-hatched and adults of Biomphalaria glabrata. The extract was obtained, characterized and its toxicity analyzed by snail embryotoxicity test (144 h) and acute toxicity test with newly-hatching and adult snails (96 h). Results showed the presence of fl avonoids, anthraquinone heterosides, coumarins and tannins in the crude ethanolic extract, which showed molluscicidal activity against all life cycle stages of B. glabrata. The LC 50 for embryos, newly-hatched and adults were 27.06, 30.60 and 55.55 ppm, respectively. Embryos exposed to the extract at 50 ppm showed hatching inhibition and at 6.2 and 25 ppm had the highest rates of morphological alterations, such as shell malformations and coagulation of the perivitelline substance. Adult snails exposed to the extract at 75 ppm showed a peak of behavioral changes, such as lethargy and shell reclusion, in addition to answers like hemolymph release in most concentrations. Further studies are required, prioritizing toxicity testing on non-target organisms and further elucidation of the active molecules.

This study analyzed the parasitism by Clinostomum sp. metacercariae of the neotropical fi sh Cichlasoma paranaense (Kullander 1983) and environmental variables' infl uence on their host-parasite relationship in Central Brazil. Fish were collected in fi ve impoundments (I) from three towns: Itauçú (n = 2), Inhumas (n = 1), and Goiânia (n = 2), Goiás State, Brazil. Ninety-fi ve fi sh were analyzed, weighted and length measured.Afterward, the presence of metacercariae in the gills, muscles, fi ns, and body cavities was investigated. The metacercariae were fi xed in AFA solution, kept in 70% alcohol, and stained with carmine. The infection prevalence revealed that 0.64, 0.56 and 0.91% of fi sh was infected. The abundance was 4.14, 3.22 and 5.88, with a mean intensity of 6.44, 5.80 and 6.42 per impoundment (I 13, I 15 and I 16), respectively. The frequency of metacercariae was higher in fi sh collected in Goiânia. High frequency of parasites was observed in the gills, muscles, and fi ns. The limnological variables did not present direct interference in the parasitism. The fi sh' standard length infl uenced the number of metacercariae positively but did not differ to the relative condition coeffi cient.