The parasitic status in the coypus (nutrias) Myocastor coypus , both farm-bred or free-living on river banks, was determined. The evaluation of faeces from farm-bred coypus indicated infection with the following parasites: Trichuris sp., Strongyloides sp., Trichostrongylus sp., Eimeria seidelli , Eimeria nutriae, Eimeria coypi , and Eimeria myopotami . Free-living feral rodents harboured Eimeria nutriae, E. coypi, Strongyloides sp. and in one case also Trichuris sp. An additional visceral examination of 20 coypus originating from five farms revealed two nematode species in the gastrointestinal tracts, namely Trichuris myocastoris and Strongyloides myopotami. The study indicated that feral coypus are far less parasitized than their captive counterparts.