Chitosan's Role in Enhancing Rearing Parameters in Bacterial-infected Silkworms

This study evaluated the efficacy of silkworm-pupal chitosan, extracted via standard methods deproteinization, demineralisation and deacetylation against Staphylococcus aureus and Bacillus thuringiensis infections in third-instar FC1×FC2 hybrid silkworms. Following oral inoculation, silkworms received chitosan treatments at four concentrations (3500, 4000, 4500 and 5000 ppm), along with ampicillin (1000 ppm), commercial chitosan (1000 ppm), solvent, absolute and un-inoculated controls. Treatments were applied to mulberry leaves at 6, 12, 18, 24 and 30 hours post-inoculation (hpi). Key parameters recorded included larval weight, disease incidence, mortality, effective rearing rate and cocoon weight. The results showed a clear dose-dependent response, with the 5000 ppm chitosan treatment applied at 6 hpi yielding optimal outcomes across all metrics, highest larval weight (33.45 g/10 larvae), lowest disease incidence (24.5%), reduced mortality (26.4%), improved rearing success (73.6%) and satisfactory cocoon weights (1.640 g). Although ampicillin remained the most effective overall, high-dose chitosan performed comparably well, particularly when applied early. Notably, pathogen-specific differences emerged, with B. thuringiensis leading to poorer outcomes than S. aureus, highlighting the need for tailored chitosan interventions. Early application markedly enhanced treatment efficacy. These findings support the use of high-concentration silkworm-pupal chitosan as an eco-friendly, antimicrobial alternative in sericulture, capable of preserving larval health and maximizing cocoon production when used promptly after bacterial exposure.