Endoparasites of the raccoon dog (Nyctereutes procyonoides) and the red fox (Vulpes vulpes) in Denmark 2009–2012 – A comparative study

Invasive species negatively influence the biodiversity of invaded ecosystems and may introduce pathogens to native species. The raccoon dog is a very successful invaded Europe and has recently invaded Denmark. The present study included analyses of Trichinella spp. and gastrointestinal helminths from 99 raccoon dogs and 384 native red foxes collected from October 2009 to March 2012. The sedimentation and counting method revealed that raccoon dogs and foxes respectively harboured 9 and 13 different helminth species, of which several were of zoonotic significance. Significantly more nematode and cestode infections were found in foxes while raccoon dogs had more trematode infections. Rodent transmitted parasites were more prevalent in foxes, while amphibian transmitted parasites were more prevalent in raccoon dogs. Only one fox was infected with Echinococcus multilocularis (0.3%), while no Trichinella spp. were detected. The trematode Brachylaima tokudai was detected for the first time in Denmark in 5 of 384 foxes (1.3%). Prevalences of Pygidiopsis summa (3.0 and 3.4%) and Cryptocotyle spp. (15.2 and 15.4%) were comparable in raccoon dogs and foxes, respectively. Four worm species were more prevalent in foxes than in raccoon dogs: Toxocara canis (60.9% and 13.1%), Uncinaria stenocephala (84.1% and 48.5%), Mesocestoides spp. (42.7% and 23.2%) and Taenia spp. (30.7% and 2.0%), respectively. Whereas three helminth species were more prevalent in raccoon dogs than in foxes: Dipylidium caninum (5.1% and 0.3%), Mesorchis denticulatus (38.4% and 4.2%) and Alaria alata (69.7% and 34.4%), respectively. Toxocara canis was more abundant in foxes while A. alata was more abundant in raccoon dogs. The intestinal distribution of a number of helminth species was comparable between hosts, but highly variable between parasite species. Inherent biological factors and host invasion to new areas might have shaped the marked differences in helminth fauna between the invasive raccoon dog and the native red fox.