Epidemiological Survey of DNA Viruses in Non-Native Pond Sliders (Trachemys scripta) in Northeastern Italy

The spread of non-native freshwater turtles in urban, peri-urban, and natural environments poses increasing ecological and sanitary concerns, particularly due to their potential role as reservoirs of infectious agents. Among these, DNA viruses remain largely unexplored in both invasive and native chelonians. In this study, a molecular survey targeting selected viral pathogens was conducted on oral and cloacal swabs collected from non-native freshwater turtles from natural and confinement ponds in Northeastern Italy, with the aim of assessing the pathogen's presence and their potential epidemiological relevance. One hundred sixty-four pond sliders (Trachemys scripta) were sampled from three sites: Herpesviruses and ranaviruses were not detected; in contrast, adenoviruses were frequently identified (72/163, 44.2%). Sequence analyses allowed their classification mostly as Testadenovirus trachemys, with only a single detection of a strain closely related to siadenoviruses and previously associated with mortality events in other tortoise species. Although the pathogenic significance of these viruses remains unclear, their detection highlights the potential role of non-native turtles as viral carriers and underlines the need for systematic virological surveillance in non-native species, particularly in ecosystems shared with susceptible native fauna.