A loop‐mediated isothermal amplification assay to detect insect‐associated <i>Serratia</i> spp. in the critically endangered insect <i>Dryococelus australis</i>

Abstract Point‐of‐care diagnostic methods are being increasingly employed to monitor infection risks in animal populations. These approaches are particularly valuable for ex situ invertebrate conservation programmes that often involve large numbers of individuals and where the rapid return of results supports timely risk mitigation decisions. Insect frass is a useful substrate to screen for the presence of pathogens transmitted by the faecal‐oral route in live insects but can result in false negatives when using common nucleic acid detection techniques, such as polymerase chain reaction (PCR), because of poor DNA extraction yields and the presence of inhibitors. We developed a diagnostic test to detect potentially entomopathogenic Serratia spp. in the frass of captive Dryococelus australis , using a cleanup step to improve DNA extraction by separating and concentrating bacterial cells, and a loop‐mediated isothermal amplification (LAMP) assay targeting the ureD gene. The LAMP assay had 1000 times greater analytical sensitivity than quantitative PCR when testing frass, did not yield false positive reactions when used to test a panel of 102 non‐ Serratia spp., achieved results in 30 min and required only basic equipment. We applied the assay in real‐life conditions to screen captive insects, yielding information about the enclosures, life stages and insect species shedding potential entomopathogens, to inform the biosecurity and management practices of the captive breeding and conservation programme for D. australis . This diagnostic test could be modified for use in field conditions and adapted to detect other pathogens of concern in invertebrate conservation programmes and for insects reared in captivity for research or agricultural purposes.