Fly on the wall: Using blow flies (Diptera: Calliphoridae) as biological monitors of wildlife pathogens

Blow flies naturally sample DNA while interacting with decomposing tissue and can be used to non-invasively monitor vertebrate populations. With emerging wildlife diseases, the ability to use flies as biological sentinels is the next step to tackling One Health problems. However, a foundational knowledge of pathogen transmission potential and detection in blow flies remains limited. Therefore, this study aims to assess the feasibility of using wild caught blow flies as biological monitors for wildlife pathogens in the field. Proof-of-concept experiments were conducted to determine if DNA from a targeted wildlife pathogen, Histomonas meleagridis, causative agent of deadly histomoniasis in turkeys, could be detected in the black blow fly Phormia regina (Meigen) and to assess persistence of H. meleagridis DNA. Three-day old lab-reared adult flies were individually exposed for four hours to either water, store-bought turkey fillet, or H. meleagridis-infected turkey liver or cecum. After exposure, three females and three males were freeze-killed at six timepoints: 0, 24, 72, 96, and 120 hours. Flies underwent gut dissection, DNA extraction, and PCR with Histomonas specific primers. Current results demonstrate that H. meleagridis DNA can be detected in blow flies; results from time trials are pending. Field collections and rapid molecular methods will be implemented to evaluate the feasibility of wild flies as pathogen sentinels in Knoxville, Tennessee and the Great Smoky Mountains National Park. This work will lay the foundation for utilizing flies as passive environmental sentinels to assist in wildlife disease diagnostics and mass mortality events by harnessing forensic entomology concepts.