Abstract Plant-derived molluscicides have been indicated as biodegradable and low-cost 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 flavonoids, anthraquinone heterosides, coumarins and tannins in the crude ethanolic extract, which showed molluscicidal activity against all life cycle stages of B. glabrata. The LC50 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.

The reproductive activity of Biomphalaria glabrata exposed to Euphorbia splendens var. hislopii latex was evaluated. Parameters related to fecundity and fertility were observed. The snails were exposed to the LD50 (1 mg/l) of crude latex. At the first week post exposure (p.e.), the egg laying was reduced. After the fourth week p.e., an increase of the number of eggs/snail occurred. The results showed a marked reduction in the hatching of the snails, revealing an interference of latex exposure with the reproductive process of B. glabrata of E. splendens var. hislopii. The LD50 of the latex may be used as an alternative method to control the size of the populations of B. glabrata in field.

O Stryphnodendron adstringens e o Caryocar brasiliensis são espécies nativas do Cerrado e vem sendo testadas como forma alternativa no controle de parasitoses e vetores. Este trabalho avaliou a ação dos extratos bruto etanólicos das cascas destas espécies na concentração de 400 ppm, sobre a parasitemia do Trypanosoma cruzi. Camundongos foram infectados por via intraperitoneal com 1x104 formas tripomastigotas do parasito e após 24 h, inoculados por via intragástrica com dose única diária dos extratos durante dez dias. A avaliação de parasitemia foi efetuada em intervalos de 48 h até a morte dos animais. Os resultados demonstraram que durante as quantificações, os extratos de S. adstringens e de C. brasiliensis apresentaram uma significativa interferência sobre a curva de parasitemia do T. cruzi, reduzindo o número de parasitos no sangue.

Crude extracts from barks of Stryphnodendron adstringens and Caryocar brasiliensis, native species of Cerrado, have been screened at 400 ppm for antiparasitic activity against Trypanosoma cruzi. Mice were inoculated with 1x104 parasites, after 24 h they were treated with one day dose extracts during ten days. The trypanosomicidal activity was evaluated each 48 h until animals death. The extracts of S. adstringens and C. brasiliensis decreased significantly the number of parasites in the blood.

The freshwater snail Biomphalaria glabrata is an intermediate host of the trematode Schistosoma mansoni. However, some strains of B. glabrata are resistant to successful infection by S. mansoni larvae. The present work examines the profile of organic acids present in S. mansoni-resistant and -susceptible strains of B. glabrata, in order to determine whether the type of organic acid present is related to susceptibility. The organic acids were extracted from the hemolymph of two susceptible B. glabrata strains (PR, Puerto Rico and Ba, Jacobina-Bahia from Brazil), and from the resistant strains 13-16-R1 and 10R2, using solid phase extraction procedures followed by high performance liquid chromatography. The organic acids obtained were analyzed and identified by comparison with known standards. Pyruvate, lactate, succinate, malate, fumarate, acetate, propionate, ß-hydroxybutyrate and acetoacetate were detected in all hemolymph samples. Under standard conditions, the concentration of each of these substances varied among the strains tested and appeared to be specific for each strain. An interesting variation was the low concentration of pyruvate in the hemolymph of PR-snails. Only the concentration of fumarate was consistently different (p£ 0.05) between resistant and susceptible strains

Um total de 4.298 exemplares de Bradybaena similaris foram coletados na zona rural do município do Rio de Janeiro e nos municípios de Paracambi e Itaguai, RJ, entre outubro de 1983 e setembro de 1986. Destes caramujos, 2.005 apresentaram metacercárias livres na cavidade pericádica. As prevalências médias anuais foram de: 42,89% (primeiro ano), 43,42% (segundo ano) e 55,86% (terceiro ano). As metacercárias foram identificadas, através de infecções experimentais em pintos, como sendo de Posttharmostomum gallinum. A pouca variação de tamanho entre as metacercárias de um mesmo hospedeiro indica que não existe um recrutamento contínuo do parasito. Análise estatística mostrou que não existe correlação entre o tamanho do caramujo e o número de metacercárias presentes na cavidade pericárdica, e que a mortalidade dos caramujos, observada em laboratório, era devido à infecção parasitária.

A total of 4,298 snails Bradybaena similaris were collected from the rural area of Rio de Janeiro County and from the Counties of Paracambi and Itaguai, State of Rio de Janeiro. Two theousand and five of these snails had metacercariae in their pericardial cavity. The cllecting was done between October 1983 and September 1986. The anhual average prevalences were: 42.89% (1st year), 43.42% (2nd year) and 55.86% (3rd year). Experimental infection in chicks allowed the identification of these metacercariae as Postharmostomum gallium. The small variation in size observed among metacercariae from the same host indicates that recruitment does not occur on a continuous basis. Statistical analysis showed no correlation between the snail size and the number of metacercariae in the pericardical cavity, and that the snail mortality observed in the laboratry was due to the parasitic infection.