Poor Parasite Community of an Invasive Alien Species: Macroparasites of Pallas's Squirrel in Italy

The aim of the present study was to investigate the macroparasite fauna of Pallas's squirrel, Callosciurus erythraeus, native to SE Asia, recently introduced to Italy and co-occurring with the native Eurasian red squirrel Sciurus vulgaris. A total of 161 Pallas's squirrels harboured a poor macroparasite fauna, characterized by two main ectoparasite species, the flea Ceratophyllus (M.) sciurorum sciurorum (prevalence 50%, mean intensity 1.0 ± 0.1) and the tick Ixodes ricinus (prevalence 47%, mean intensity 3.0 ± 0.7), and a few helminths (Rodentoxyuris sciuri, Trichuris muris, Strongyloides callosciureus) all with prevalence below 10%. All parasites, except S. Callosciureus, are native to Europe and were acquired in the invaded range. The loss of native parasites might have contributed to their successful invasion. The acquisition of local parasites C. Sciurorum and Trichuris sciuri, and the introduction of the Asiatic nematode S. Callosciureus may lead to spill-back and spill-over processes towards red squirrels.