Chitosan infused resilience: Uplifting cocoon and post cocoon traits in silkworms infected with bacterial infections

Abstract

To utilize waste silkworm pupae from the silk-reeling unit by extracting chitosan, an experiment was carried out to evaluate the efficacy of the extracted chitosan against bacterial diseases affecting the silkworm, Bombyx mori L. by assessing its impact on cocoon and post cocoon quality parameters. The efficacy of chitosan was evaluated by the bioassay technique using the leaf dip method against silkworms infected with bacterial pathogens, Bacillus thuringiensis and Staphylococcus aureus. Among the bacterial infected silkworm’s, ampicillin applied at 1000 ppm showed the strongest resistance to bacterial stress and recorded the best compared to all the treatments. This was followed by the chitosan concentrations at 5000 ppm, which recorded the highest cocoon weight (1.64 g), pupal weight (1.31 g), shell weight (0.32 g), shell ratio (19.57%), filament length (936.41 m), filament weight (0.27 g) and filament denier (2.60) among the chitosan concentrations. All chitosan concentrations performed comparable to the standard ampicillin treatment and commercial chitosan at 1000 ppm. In contrast, bacterial-infected silkworms without any treatment (absolute control) recorded the lowest cocoon weight (1.44 g), pupal weight (1.16 g), shell weight (0.28 g), shell ratio (19.15%), filament length (733.41 m), filament weight (0.21 g) and filament denier (2.61). Meanwhile, the un-inoculated silkworms recorded the highest cocoon weight (2.04 g), pupal weight (1.62 g), shell weight (0.41 g), shell ratio (20.10%), filament length (1142.63 m), filament weight (0.33 g) and filament denier (2.58) among all the treatments. After the application of chitosan concentrations, B. thuringiensis infected silkworms resulted in lowest cocoon parameters with shorter and lighter filaments compared to S. aureus indicates the severity of pathogen. A clear dosage and time dependency was observed, where early application (6 HPI) and higher concentrations of chitosan (4500-5000 ppm) significantly enhanced resilience. The results suggest that silkworm-derived chitosan, especially at 5000 ppm, can approximate the effectiveness of antibiotics under controlled rearing conditions.