An Expanding Population of the Giant Liver Fluke (Fascioloides Magna) in Elk (Cervus Canadensis) and Other Ungulates in Canada

A resurgence of the giant liver fluke (Fascioloides magna) in the Canadian Rocky Mountain Parks, previously extirpated by the 1960s, has been documented through a two-decade study. The research, conducted between 1984 and 1991, revealed a significant increase in fluke prevalence among elk (Cervus canadensis), reaching near-universal infection rates (79–100%) by the late 1980s. Super-infections with over 100 flukes became more common, and transmission peaked in wet habitats during late summer to fall. While elk and white-tailed deer (Odocoileus virginianus) were primary hosts, moose (Alces alces) also showed high prevalence (52–63%), whereas mule deer (Odocoileus hemionus hemionus) had minimal exposure. The study highlights the fluke's adaptability and its potential to cause fatal infections, with at least seven elk deaths attributed directly to F. magna. The findings underscore the need for monitoring in UNESCO-listed areas where ecological shifts may facilitate parasite expansion.

Pybus, M. J., Butterworth, E. W., & Woods, J. G. (2015). AN EXPANDING POPULATION OF THE GIANT LIVER FLUKE (FASCIOLOIDES MAGNA) IN ELK (CERVUS CANADENSIS) AND OTHER UNGULATES IN CANADA. Journal of Wildlife Diseases, 51(2), 431–445. https://doi.org/10.7589/2014-09-235