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Accumulation of heavy metals in tissues of the crayfish Procambarus clarkii and in water were evaluated in areas located in the Egyptian Delta (Gharbiya, Kafr El-Shaikh, and Menofiya) in 2010 and 2021. Statistics showed that in 2010 the highest concentration of heavy metals in the digestive gland and in muscles was Zn, both in Gharbiya and Menofiya, while Fe was the highest accumulated in the digestive gland, and Pb was the highest in muscles of samples from Kafr El-Shaikh. The results showed that heavy metal loads decreased in Kafr El-Shaikh in 2021, whereas Fe increased significantly () in Gharbiya and Menofiya (41.44 ± 2.32, 47.25 ± 2.64 μg/g). Accumulation of Cd and Zn in gills and muscles decreased in all areas from 2010 to 2021, while a significant increase () was shown in Fe and Cu in 2021. All heavy metals significantly decreased () in waters of the studied areas from 2010 to 2021.

Controlled-release technology was introduced to offer an incredible guarantee for improving the adequacy of the existing active molecules and solving the related environmental troubles. Our study attempts to utilize the controlled release of alginate niclosamide-l-glutamate formulation to control Schistosoma mansoni intermediate host (Biomphalaria alexandrina snail) and to evaluate the amount of niclosamide released in relation to its attraction and mortality rate. Results: polymeric formulations B3-4b at a concentration of 0.3 ppm niclosamide in combination with 75% l-glutamate caused 100% mortality of B. alexandrina snails 5-day post-exposure. Stable snails mortality rates were obtained post-exposure to polymer B3-4a (R2 = 0.9823). The high potential of the polymeric formulations B3-4a (0.2 ppm niclosamide and 75% l-glutamate) to attract snail toward polymer direction was manifested by 80%, 14%, 6% and 0% snail in areas (I), (II), (III) and (IV), respectively 24-hr post-exposure. While, B3-4a showed a high mortality rate of attracted snails resembled by 40% and 100% on the 2nd and 7th days, respectively. The modified structure of polymer-niclosamide-l-glutamate prolonged the validity and efficiency of the niclosamide. Slowly released molluscicide was effective at lower concentrations with increasing concentrations of the applied attractant that could reduce its toxicity to the water ecosystem. Keywords: Biomphalaria alexandrina, Control of schistosomiasis, Controlled release molluscicides, l-glutamate attractant, Niclosamide

In this study, the chronic effects of diethyldithio carbamate (DDC) on the fecunditiy and on some oxidative and anaerobic enzymes of Biomphalaria alexandhna snails, the intermediate host of Schistosomiasis mansoni in Egypt, were evaluated. The data obtained showed that the exposure of snails to sublethal concentrations of DDC reduced the egg laying capacity of the snails. The hatchabilily and survival rates of eggs, treated with very low concentrations of DDC were significantly reduced. All of the above effects were found lo be concentration and time dependent. Also, these DDC concentrations resulted in a significant decrease in the activity of lactate oxidase (LO), succinate oxidase (SO), known to activate vitellogenesis, and pyruvate kinase (PK), the key enzyme of anaerobic metabolism. On the other hand, the levels of transaminases (AST, ALT) of the exposed snails to DDC concentrations tested were not affected. At the same time, the glycogen content of the treated snails was lowered significantly. Moreover, the tested DDC concentrations caused degenerative changes to