Isolation and identification of bacterial pathogens causing infections in Bombyx mori

Abstract

The present research was conducted at the sericulture unit, University of Veterinary and Animal Sciences, Pakistan to assess the influence of different mulberry species viz., Morus alba, Morus nigra and mixed mulberry leaves diet on the health and disease susceptibility to Bombyx mori. The silkworms were reared under semi-controlled conditions and optimum temperature (25-28°C) and humidity (70-80%) was maintained during experimental period. The proximate analysis of the mulberry leaves showed significant nutritional variations and higher crude protein was reported in Morus nigra as compared to Morus alba and mixed leaves. The isolation of bacteria from diseased silkworms revealed 157 distinct colonies from different sources. The highest number of colonies was observed in samples taken from the gut (62 colonies), followed by the whole body (53 colonies) and the outer body surface (42 colonies). The Pearson’s correlation analysis (Pearson’s r = 0.87, p < 0.001) revealed a strong association between the severity of disease symptoms and bacterial load especially in the gut-derived samples. Preliminary identification based on colony morphology, growth characteristics and simple biochemical tests suggested the presence of multiple bacterial species including potential pathogens such as Staphylococcus spp., Escherichia coli and possibly Bacillus spp. These findings suggested that diet significantly affects silkworm’s overall health and disease susceptibility as black mulberry leaves possibly offering benefits in terms of bacterial resistance. Recommendations include adopting mixed mulberry leaves diets and enhancing sanitary measures to improve overall health and productivity in sericulture.