Understanding Vectors and Fomites and Overcoming Their Challenges in Edna Monitoring

The use of environmental DNA (eDNA) has great promise as a tool for resource managers to quickly detect the presence or absence of invasive species, rare or endangered species or pathogens. Environmental DNA is currently used to monitor for the presence of Asian carp throughout the Chicago Area Waterway System, Great Lakes and Upper Mississippi River. Currently, detection of Asian carp DNA in an eDNA sample only indicates the presence of DNA, not its route of entry. Vectors of DNA transmission from locations with to locations without have generally not been evaluated. Characterizing the potential for vectors to transfer DNA is critical to accurate interpretations of DNA detected in environmental samples. We performed trials to assess piscivorous birds as a vector of Asian carp DNA transfer. Trials were performed by feeding silver carp to bald eagles (Haliaeetus leucocephalus), white pelicans (Pelecanus erythrorhynchos) and double-crested cormorants (Phalacrocorax auritus), returning the birds to a silver carp free diet and then sampling their excrement for 7 days. Results suggest Asian carp DNA can be detected in bird excrement for 5 days post-feeding. Silver carp DNA persisted in bird feces on metal surfaces for more than 30 days post deposit. Degradation was assessed using markers of various lengths (≤ 1387 base pairs). Approaches may be useful to limit the influence of birds and other vectors of eDNA when interpreting detection of Asian carp DNA or other target species.