Biological invasions are occurring at an unprecedented rate around the globe. Their impact on biodiversity is mediated both by direct competition with native species and by the alteration of transmissible disease dynamics. The red eared slider Trachemys scripta is considered one of the most successful invasive species across Europe, and has proved to be a stronger competitor with the native freshwater turtle Emys orbicularis . Nevertheless, few studies have explored parasites of T. scripta in the countries of introduction. Aiming to explore the taxonomic helminth composition of T. scripta and assess potential spillover risks to E. orbicularis , a population of red eared sliders was sampled from a protected area in Northeastern Italy, where the two turtle species co-exist. Sixty-two animals were humanely euthanised and submitted to complete parasitological investigation. Morphometric and molecular data were combined to identify the helminths to species level. Overall, 68.4% of the animals were positive for helminths. Three species were recovered from the gastrointestinal tract, namely Telorchis corti (Digenea: Telorchiidae), Polystomoides oris (Monogenea: Polystomatidae), Serpinema microcephalus (Nematoda: Camallanidae) and one from the urinary bladder, Polystomoides orbicularis . Three of the four species retrieved are considered exotic, two of them already reported in Southern Europe also in native species. Pancreatic lesions were observed in association to S. microcephalus , demonstrating enhanced pathology in this host. Studies on E. orbicularis are recommended to shed light on patterns of parasite exchange among the two emydid species. Additionally, a wider survey across the national territory is advised to further explore the helminth composition hosted by this invasive species.
Marchiori et al. (Fri,) studied this question.