Insects as Natural Hosts, Vectors and Reservoirs of Botulinum Neurotoxin-Producing Clostridia and Their Non-Toxinogenic Counterparts: Preliminary Evidence.

Insects play a significant role in the transmission and spread of bacterial pathogens that cause various diseases in humans and animals. The relationship among insects, bacterial pathogens and diseases is complex and depends on the specificity of the pathogens. Some clostridial species produce botulinum neurotoxin (BoNT), which is responsible for paralytic botulism. However, the ecology of these bacterial species and their non-toxinogenic phylogenetic counterparts remains unclear. This study specifically explored in silico evidence of the interconnection between BoNT-producing Clostridia and their non-toxinogenic counterparts with insects. Based on literature meta-analysis, the mining of 16S rRNA amplicon and metagenomic sequencing datasets and a pilot feeding experiment in the Glanville fritillary butterfly, Melitaea cinxia, we propose that BoNT-producing Clostridia and their non-toxinogenic phylogenetic counterparts are carried internally and/or externally in different insect orders. While previous case studies have indicated associations between Clostridia and insects, this work provides a more comprehensive view of their occurrence. It also highlights the need for further multidisciplinary investigations to characterise the natural ecology of BoNT-producing Clostridia and their non-toxinogenic counterparts in insects.