Microbial pathogens of edible insects: a growing problem for the insect farming industry

Insect farming is widely extolled as a sustainable alternative to the traditional agricultural production of protein for human and animal consumption. However, pathogen contamination endangers insect health, food safety, production yields and market acceptance. Because insect farming is intensive, growth and transmission of pathogens are promoted, elevating the risk of disease outbreaks with severe economic outcomes. Fungal pathogens can invade host insects through their cuticle, reproducing within the nutrientrich haemolymph within the haemocoel until the host's defences are overwhelmed and the insect dies. Other pathogens, such as viruses, oomycetes and bacteria, enter the host orally before penetrating the midgut wall to infect the haemolymph. Even apparently healthy farmed insects carry a diverse array of potentially pathogenic bacteria/fungi within their guts, as well as sub-lethal viral infections, and these covert infections can quickly become epizootic breakouts. Consequently, there is an urgent need to understand the infection and transmission of pathogens in insect farms, as well as to develop strategies to prevent and treat infections/outbreaks. This review collates information about the susceptibility of farmed insects to infection by fungi, bacteria, viruses, nematodes and other parasites, current pathogen detection methods, and possible control measures, with the aim of making this information accessible to practitioners and researchers of insect farming. We suggest that prophylactics/treatments are urgently needed by insect farms, alongside improvements in infection control, to ensure the long-term viability and acceptance of edible insects as a sustainable alternative protein source.