Pattern of parasite egg shedding by European bison (Bison bonasus) in the Biaowieza Primeval Forest, Poland

We investigated the pattern of parasite egg shedding by European bison (Bison bonasus) in the Biaowieza Primeval Forest. We found several groups of parasite eggs in bison faeces including Trichostrongylidae, Nematodirus spp., Aonchotheca sp., Trichuris sp. and Moniezia spp. Trichostrongylidae eggs were expelled from bison at the highest percentage (27.8 %) but in low numbers. The prevalence (percentage of faeces with parasite eggs) of other parasites did not exceed 12 %. The number of detected eggs of the parasite species differed: The highest was in Trichuris sp. and Moniezia spp. There were no significant differences in prevalence between male and female bison, with exception of Trichuris sp. whose eggs were more often detected in female faeces. The number of eggs per gram (EPG) of faeces was significantly higher in females for Aonchotheca sp. Parasite prevalence showed seasonal variation and was significantly higher for Trichostrongylidae, Nematodirus spp., Aonchotheca sp. and Moniezia spp. parasites in winter (December-March) compared to the snow-free period (April-November). We observed a 3-14 fold higher prevalence of these parasites in winter compared with the snow-free period. We assumed that factors such as season and bison sex have an influence on the level of excreted eggs. The determination of the factors affecting the rate of parasite egg excretion into the environment is important for the management of wild animals, especially endangered species such as the European bison.