Insect rearing on manure: are micro-organisms and antibiotics being transferred from the substrate to the larvae?

Insects are believed to be a sustainable protein alternative for feed and food, however, food safety is an important factor.This study aimed to assess the microbiological and chemical risks from rearing black soldier fly larvae on solid pig manure. Additionally, two washing procedures were evaluated. The manure was spiked with Listeria spp. or antibiotics. Fresh manure, harvested larvae, and residual substrate were analysed for dry matter content, microbiology, and the presence of antibiotics. Larvae were washed with a physiological water (10 washing steps) and with ethanol and analysed in both cases. A transfer of micro-organisms and antibiotics from the substrate to the larval biomass was found. For substrates, other than manure, the same transfer mechanism may result in contamination of the larval biomass. For the larval growing stage, we could not establish an effective washing procedure. Farming insects for feed or food certainly needs special attention.