Chitosan Nanoparticles: A Dual Approach for Mollusk and Infection Control in <i>Biomphalaria alexandrina</i> Snails

Chitosan nanoparticles (CNPs), derived from crab shells, are eco-friendly and effective molluscicides. Their enhanced bioactivity makes them ideal for controlling disease-carrying mollusks, including freshwater snails that transmit Schistosomiasis. This study evaluates the molluscicidal effects of chitosan nanoparticles on Biomphalaria alexandrina snails, including those infected with Schistosoma mansoni, to assess their potential in schistosomiasis control. Chitosan nanoparticles were synthesized by dissolving 0.6% chitosan in 1% acetic acid, adjusting the pH to 4.7, and adding 0.3% TPP under stirring. Sublethal doses (LC₁₀: 49.78 ppm, LC₂₅: 59.02 ppm) were tested on Biomphalaria alexandrina to evaluate toxicity to B. alexandrina snails, effects on laying eggs and their survival rate, hormonal changes, and histological effects in Schistosoma mansoni-infected snails. Flow cytometry assessed Annexin-V levels, survival, infection rate, lifespan, and cercarial production. Sublethal doses (LC₁₀ and LC₂₅) of chitosan nanoparticles significantly reduced snail fecundity and reproductive rates. Hormone levels (progesterone, 17-β estradiol, estrogen, and testosterone) declined notably after treatment. Histological analysis revealed extensive cellular damage, vacuolation, and degeneration, particularly in the head-foot region at 3 and 21 days post-infection with S. mansoni. The percentage of apoptotic cells increased, with a notable rise in late apoptosis and necrosis in infected snails treated with LC₂₅ ppm. Exposure to chitosan nanoparticles also led to reduced Schistosoma mansoni infection rates and cercarial production at 3 and 21 days post-infection with S. mansoni. This study confirms the potent molluscicidal effects of chitosan nanoparticles on Biomphalaria alexandrina, reducing reproduction, hormonal levels, and infection rates while inducing apoptosis and histological damage. CNPs show promise as an eco-friendly tool for schistosomiasis control.