SUMMARY
Giant American liver fluke Fascioloides magna is a parasite from the Trematoda class, which is of a great epizootiological importance for both deer and local ruminants. The parasite significantly influences the deer health status. Importantly, the deer also spread the parasite eggs in the environment infesting the local ruminants (cattle, sheep, goat) thus creating great economic losses. The fluke appeared in Europe for the first time in the nineteenth century when the invaded American deer was imported. Over the last decades, F. magna was detected in many European countries, recently even in Croatia (Baranja region).Bosnia and Herzegovina is a natural habitat of the population of European deer (Cervus elaphus) along the border with Croatia, following the water course of the Sava river from Kozara to Semberija so that the seasonal migration of deer from Croatia and back have been observed. Such natural migrations may pose a big epizootiological problem in terms of fascioloidosis spread in Bosnia and Herzegovina. The breakout of fascioloidosis would threaten endangered wild populations, but also the regional livestock. For this reason, the priority of our country as well as the neighboring countries should be cross-border monitoring of game and registering the deer parasitic fauna to prevent the spread of fascioloidosis and other parasitosis, in order to prevent further losses in the already poor livestock breeding. Key words: migration, deer, Fascioloides magna, Bosnia and Herzegovina