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Bacterial and fungal microbes associated with cricket rearing systems in the tropics

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posted on 2024-07-01, 12:26 authored by R.P.M. Nyombe, B. Odhiambo, P. Bulli

House crickets (Acheta domesticus) and field crickets (Gryllus bimaculatus) are among the commonly reared insects for human and animal consumption. However, the potential contamination of rearing facilities with microbes poses a serious threat to sustainability of production of these insects, especially in poorer regions of the world where strategies for ensuring microbe-free environments are lacking in most cases. In this study, bacterial and fungal communities associated with cricket-rearing facility under partially controlled conditions were isolated and examined using morphological and molecular marker-based approaches. BLAST analysis of amplified 16S rRNA sequences revealed similarities to the bacterial genera Rickettsiella, Enterobacter, Bacillus, Levilactobacillus, and Aeromonas, while analysis of the ITS sequences revealed similarities to the fungi Pithomyces spp., Fusarium spp., Aspergillus spp. and Tetrapisispora spp. Increased mortality and reduced nutritional contents of crickets exposed to the bacterial and fungal microbes were evident. Of notable concern is the contamination of the crickets with spore-forming bacteria and toxin-forming bacteria as well as fungi. Although the levels of mycotoxin were relatively low compared to the threshold set by many countries in sub-Saharan Africa, the detection of aflatoxin in both species of crickets is of great concern as any dosage can pose serious health risks to consumers. Strategies to minimize contamination of crickets by entomopathogenic microbes are outlined, and future areas of research are suggested.

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