Immunotoxical, neurotoxical, histopathological and immunohistopathological alterations of Nerium oleander and Tecoma stans methanolic extract on Biomphalaria alexandrina snails.

• B. alexandrina snails are the intermediate host of schistosomiasis mansoni. • Nerium oleander and Tecoma stans methanolic extracts have molluscicidal activities. • Both extracts exert Immunotoxical, neurotoxical and immunohistopathological disturbances of treated snails. • Nerium oleander more potent molluscicide than Tecoma stans methanolic extracts. • Both plants are cheap and ecofreindly to replace the synthetic molluscicides for snail control. Schistosomiasis is a severe illness that caused socioeconomic problems. The present study aimed to investigate the molluscicidal activities of the methanolic extract of Nerium oleander and Tecoma stans on B. alexandrina snails. The present results showed that N. oleander had the higher molluscicidal effect (LC 50 : 138.6 mg/l) than T. stans methanolic extract (LC 50 : 256.0 mg/l). These concentrations had no mortality effects on Daphnia magna during the first 12 h of the exposure, while, they had a cercaricidal activity. Exposure of B. alexandrina snails to the sub lethal concentrations (LC 10 and LC 25) of the methanolic extract of either N. oleander or T. stans caused a concentration- dependent significant decrease in their mean total number of hemocyte and hyalinocytes percent, while, both the round small and the granulocytes were increased than the control group. Exposure of B. alexandrina snails to LC 25 of the methanolic extract of N. oleander or T. stans , caused morphological alterations in the hemocytes that were studied by both light and electron microscopy. The sub lethal concentration (LC 25) significantly decreased the acetyl cholinesterase activities, acid and alkaline phosphatase levels and the protein content. Histopathological changes occurred in the digestive and the hermaphrodite glands of exposed B. alexandrina snails to LC 25 of the methanolic extracts. These alterations were confirmed by Immunohistochemistry for PCNA and Cyclin D1 expressions. Conclusively, these plants could be used to decrease the spread of schistosomiasis as they are cheap and environmentally safe to replace the synthetic molluscicides for snail control. [ABSTRACT FROM AUTHOR]