Sparganosis is a parasitic disease caused by plerocercoid larvae of the tapeworm Spirometra sp. The first intermediate hosts are copepods; the second intermediate hosts are amphibians, reptiles, birds or mammals; final hosts are carnivores such as lynx and wolves. The disease is known mainly from Asia, and it was rarely reported in Europe. We investigated spread of this parasitic disease in mammal communities in two forests in north-eastern Poland. Three new paratenic hosts: badger, raccoon dog, and wild boar were identified. We found differences in infection prevalence between study sites as well as interspecies and interindividual variation in the infection intensity. Higher percentage of infected badgers and raccoon dogs was observed in Białowieża Forest (BF) than in Augustów Forest, which can be related to higher habitat humidity and species diversity in BF. The infection intensity was increasing with the age of the infected animals due to the longer exposure to the parasite. We also confirmed the presence of adult Spirometra sp. in final hosts, wolf and lynx, reported previously only once in BF, over 60 years ago. Moreover, we found Spirometra sp. plerocercoids in wild boar meat. The meat is not diagnosed for this parasite and since wild boar is an important game species in Europe, there is a substantial risk of infections in humans. It has therefore become a priority to inform the public of possibilities and consequences of Spirometra sp. infection and to intensify research on sparganosis. Study financed by the National Science Centre, project No. 2016/21/B/NZ8/02429.