E. globulus is a potential source for biocidal compounds against S. mansoni and its snail host. This is the first study to test the biocidal activity of the isolated compounds.

Context: Praziquantel (PZQ) is a highly efficacious anthelmintic against many flatworms including schistosomes. PZQ has been in use for more than 25 years, and concern is increasing that resistance has emerged in human schistosomes in Egypt and other endemic countries. Objective: The current study was designed to evaluate a recently described method for induction of PZQ resistance in Schistosoma mansoni. Materials and methods: Successive subcurative drug treatments of Biomphalaria alexandrina snails infected with an Egyptian strain of S. mansoni were undertaken. Cercariae shed from snails exposed and unexposed to PZQ were used to infect mice. Forty-five days after infection, mice were treated with a single oral dose of PZQ in 2% aqueous solution of Cremophor-EL Õ . The concentration of PZQ was 0, 200, 400, or 800 mg/kg. Thirty-three days after treatment, all groups of mice were dissected to collect the S. mansoni worms by the perfusion technique. In addition, the oogram pattern was examined to study the production, maturity, and death of S. mansoni eggs in the different groups of mice. Results: The present study has shown that the sublethal dose for induction of PZQ resistance in the intra-molluscan S. mansoni stages was 500 mg/kg. The worm count and the percentage of immature eggs in different groups of mice were significantly affected by the intra-molluscan exposure to PZQ and the drug concentration used to treat infected mice. Discussion and conclusion: The results obtained herein confirm the possibility of using successive drug treatments of infected B. alexandrina to induce PZO resistance in S. mansoni.

Saponin fraction from A. anthelmintica has a promising molluscicidal effect against snails for LC 50 of 17.6 ppm as well as a strong biocidal activity against the larval stages of S. mansoni (miracidia and cercariae). A high significant decrease (p<0.001) was recorded in infection rate and survival rate during continuous exposure of the plant; being 50±10 and 44.66±5.05 respectively compared with 81±10.1 in control groups respectively. Light microscopic investigation showed that the tested plant is responsible for the increase of snail's amoebocytes that is consider a main component of the internal defense system of the B. alexandrina snails. Electron microscopic examination showed remarkable apoptotic effects, nuclear chromatin condensation, vacuolated cytoplasm and deterioration in the internal organs as endoplasmic reticulum. It is concluded that exposure of B. alexandrina snails to saponin fraction from A. anthelmintica may be used as a promising molluscicidal and biocidal against the S. mansoni parasite.

Context Thais savignyi Deshayes (Muricidae) is widely distributed in the Red Sea. Its abundance and the history of Muricidae in traditional medicine make it a tempting target for investigation. Objective To investigate the chemical profile and biological activities of T. savignyi tissue extracts. Materials and methods Methanol, ethanol, acetone, and ethyl acetate extracts from T. savignyi tissue were compared in their antioxidant by total antioxidant capacity, DPPH free radical scavenging, and total phenolic content. In addition, the antimicrobial, and antibiofilm properties (at 250 µg/mL) of the extracts were tested against Escherichia coli , Pseudomonas aeruginosa , Proteus vulgaris , Klebsiella pneumoniae , Staphylococcus aureus , and Candida albicans . The antioxidant extract with greatest activity was assessed for cytotoxicity (range 0.4–100 µg/mL) against 3 human cancer cell lines (UO-31, A549 and A431), and its chemical composition was investigated using GC-MS. Moreover, docking simulation was performed to predict its constituents’ binding modes/scores to the active sites of thymidylate kinase. Results The ethyl acetate extract ( Ts -EtOAc) showed the highest total antioxidant capacity (551.33 mg AAE/g dry weight), total phenolics (254.46 mg GAE/g dry weight), and DPPH scavenging (IC 50 = 24.0 µg/mL). Ts -EtOAc exhibited strong antibacterial (MIC: 3.9 µg/mL against K. pneumoniae ), antibiofilm (MIC: 7.81 µg/mL against S. aureus ), and antifungal (MIC: 3.9 µg/mL against C. albicans ) activities and considerable cytotoxicity against cancer cells (UO-31: IC 50 = 19.96 ± 0.93, A549: IC 50 = 25.04 ± 1.15 μg/mL). GC-MS identified multiple bioactive metabolites in Ts -EtOAc extract belonging to miscellaneous chemical classes. Molecular docking studies revealed that the constituents of Ts -EtOAc have antibacterial potential. Discussion and conclusions T. savignyi extract has considerable antimicrobial and cytotoxic activities. Further studies are needed to isolate the active constituents of this snail for comprehensive drug discovery tests.

In spite of using aquatic snails as bioindicators for water pollution, little attention has been paid to the effect of parasitism upon the concentration of heavy metals (Al, Cd, Cu, Fe, Mn, Pb and Zn) in these organisms. The present study therefore aimed to compare the concentrations of heavy metals in trematode-infected Biomphalaria alexandrina collected from Kafer Alsheikh and Menofia provinces, Egypt, with uninfected snails from the same sites, in order to assess the effect of parasitism on the use of these snails as bioindicators. The concentrations of heavy metals in the soft parts and shells of snails were measured by flame atomic absorption spectrometry. The results showed that the heavy metal profile in snails infected with Echinostoma liei was very different from that in snails infected with Schistosoma mansoni. The total concentration of heavy metals in E. liei-infected snails collected from Kafer Alsheikh or Menofia province was greater than in uninfected snails. In contrast, the total concentration of heavy metals in S. mansoni-infected snails was reduced compared with uninfected snails. In conclusion, the status of snails with respect to parasitic infection must be taken into consideration when these snails are used as bioindicators.