Potential uptake and persistence of relevant feed- and food-pathogens in black soldier fly larvae (Hermetia illucens)

The insect production sector is rapidly developing and the use of organic residual streams would contribute to a circular insect sector. However, an important element is the veterinary and food safety of these residual streams. The presence of pathogens in insects or organic residual streams may impact insect health but may also cause health risks for the consumers of the insects. In this in vivo study two experiments were performed with Black Soldier Fly (Hermetica illucens) Larvae (BSFL) to study the uptake and persistence of different relevant pathogens (CSFV, FMDV, HEV, LPAIV, SVDV, Eimeria, bacteria including AMR genes, B. cereus, C. perfringens, K. pneumoniae, S. abaetutuba) at different time points (D0, D1, D3, D7) during rearing on spiked broiler manure (BRM). The results suggest that some of the studied pathogens can transmit from the substrate to the insects, but others were not detected. Infectious FMDV and SVDV were detected after spiking, but only at D1. HEV and the parasite Eimeria were detected in the BSFL during the whole experiment, suggesting a transfer from the spiked substrate. The bacteria B. cereus, K. pneumoniae and S. abaetutuba and bacteria with AMR genes were present in the spiked substrate and the BSFL during the whole experiment. However, the presence of K. pneumoniae, C. perfringens and a few colonies of B. cereus in the BSFL prior to start of the experiment makes it difficult to evaluate the uptake from spiked substrate. C. perfringens was during the study only detected in the spiked BRM and not in the larvae. This study studied spiked pathogens in not yet legalized residual stream broiler manure (BRM) used for insect rearing. Although a limited number of replicates was included, the presence of potential food and feed safety hazards in spiked broiler manure and subsequently in the unprocessed BSFL argues for future studies. These studies should focus on estimating the veterinary and food- and feed safety risks of using organic residual streams, including the risk of exposure to contaminated residue and insects, for both insects and consumers. Furthermore, research on the effect of processing and quality control methods, aiming to reduce the risk of transmission of pathogens and AMR genes into the circular production chain should get attention.