EN
Four free living European bison from Białowieża/Caucasus line shot in february 1997 within Lutowiska Forestry District in the Bieszczady Mountains were used in investigations. All examined ani mais were infected with helminths. There were found 10 species of parasites. Five species of them Ostertagia leptospicularis, O. kolchida, Spiculopteragia boehmi, Cooperia pectinata and Ashworthius sidemi are thypical parasites of Cervides, and from them were infected bison in Bieszczady. In all necropsied animals was found invasion of nematode A. sidemi, with mean intensity 1542 specimens. It is the first registration of A. sidemi in Poland and European bison is a new host for this parasite. It seems that the source of infection A. sidemi in European bison in Bieszczady is the local population of deer, which during their migrations could bring this parasite from neighbouring Ukraine and Slovakia, where this nematode have been introduced together with deer Cervus nippon. There are also presented results of coproscopic examinations of 17 fecal samples from free living European bison in Bieszczady.