Advancing pathogen surveillance by nanopore sequencing and genotype characterization of Acheta domesticus densovirus in mass-reared house crickets.

Rapid and reliable detection of pathogens is crucial to complement the growing industry of mass-reared insects, in order to safeguard the insect colonies from outbreak of diseases, which may cause significant economic loss. Current diagnostic methods are mainly based on conventional PCR and microscopic examination, requiring prior knowledge of disease symptoms and are limited to identifying known pathogens. Here, we present a rapid nanopore-based metagenomics approach for detecting entomopathogens from the European house cricket (Acheta domesticus). In this study, the Acheta domesticus densovirus (AdDV) was detected from diseased individuals using solely Nanopore sequencing. Virus reads and genome assemblies were obtained within twenty-four hours after sequencing. Subsequently, due to the length of the Nanopore reads, it was possible to reconstruct significantly large parts or even the entire AdDV genome to conduct studies for genotype identification. Variant analysis indicated the presence of three AdDV genotypes within the same house cricket population, with association to the vital status of the diseased crickets. This contrast provided compelling evidence for the existence of non-lethal AdDV genotypes. These findings demonstrated nanopore-based metagenomics sequencing as a powerful addition to the diagnostic tool kit for routine pathogen surveillance and diagnosis in the insect rearing industry.