Avaliação do efeito moluscicida dos extratos de Curcuma longa em caramujos Biomphalaria sp.não infectados e infectados por Schistosoma mansoni

Abstract

In order to effectively control schistosomiasis as a public health problem, multiple interventions are needed in addition to the diagnosis and treatment of infected individuals, such as the implementation of WASH (water, sanitation and hygiene) interventions, health education and population control of intermediate hosts using synthetic or natural substances, such as plant extracts. There are currently no specific molluscicide options (effective and safe for the environment). Niclosamide, used routinely, is harmful to fish, amphibians, certain insect larvae and, at higher doses, to aquatic vegetation, although these effects are generally short-lived. We evaluated the molluscicidal effect of Curcuma longa extract at concentrations of 10, 5 and 1 ppm on intermediate hosts of schistosomiasis, the molluscs of the genus Biomphalaria, the species being: Biomphalaria glabrata, Biomphalaria tenagophila and Biomphalaria straminea exposed to the extract. We also evaluated the maintenance of the effect and the stability of the percolated extract by repeating the experiments after 18 months to verify the action, as well as the effects of the extract on non-target species, in fish Poecilia reticulata. We used the extracts prepared in 2022 (E1) and the extract prepared in 2024 (E2) to evaluate and compare the effects on uninfected and infected Biomphalaria glabrata and E1 for Biomphalaria tenagophila and Biomphalaria straminea. The extract, obtained from the powdered rhizome, was subjected to a maceration process followed by percolation and characterization. The snails were exposed to the extracts without the presence of solvent and mortality was assessed according to exposure time (24, 48, 72, 96 and 168 hours), and then placed in deionized water after 168 hours to certify mortality. Statistical analysis was carried out using the two-way ANOVA test (concentration and exposure time). For uninfected Biomphalaria glabrata, the ethanolic extract E1 provided more significant results than the acetonic extract, with the concentration of 10 ppm being the most effective, with 90% mortality. When the experiment was repeated, the E2 extract at concentrations of 1 and 5 ppm (ethanolic) provided 80% mortality and at 10 ppm 100%.After 18 months, the ethanolic extract maintained greater effectiveness compared to the acetonic extract on the three species of Biomphalaria, being less sensitive to B. straminea. There was 100% mortality in Poecilia reticulata fish exposed to concentrations of 10, 5 and 1 ppm of the extract. According to the World Health Organization (WHO), 1983, molluscicidal potential is effective when it provides 90% mortality at 20 ppm for extract or fractions and 100 ppm for crude material, classifying an extract as active when it provides mortality between 70% and 90%. Thus, the Curcuma longa extract showed a significant molluscicidal effect on Biomphalariamolluscs, however it provided significant toxicity on non-target species, showing that its use as an alternative and specific natural molluscicide in combating the intermediate host population of schistosomes has a limited indication until further tests are carried out demonstrating in details its action in the environment.