Microbiological safety assessment of silkworm farms: a case study

Silkworms have been farmed for their silk since ancient times. After silk reeling, their chrysalides are consumed as food in several Asian countries. Despite the long rearing tradition of this insect, few studies have investigated the silkworm's microbiological safety all along the life cycle, focusing on detecting silkworm pathogens or on the safety of the dried chrysalis for food consumption. However, the in-farm rearing process, which takes around forty days, may affect the microbial load of the silkworm and of the rearing environment, as well as the quality of fresh cocoon and other performance parameters. No data is available on how microbial contamination changes during the rearing period and between different farmers. Furthermore, in light of the possible use of the chrysalis as food, it is crucial to understand how its microbial load varies according to the water content. To address these specific questions, we conducted an investigation involving the analysis of specific microbial indicators commonly used in the food chain. We collected environmental and silkworm samples from several farms. The examination covered the entire life cycle of silkworms, beginning with the first instar larvae and concluding with the scrutiny of both freshly harvested and dried pupae. Silkworm farms in Northeast Italy proved to be an appropriate model system for carrying out the experimentation. Additionally, an evaluation of rearing performance was conducted, with a focus on the quality of fresh cocoons and the survival rate of the insects.