AN EXPANDING POPULATION OF THE GIANT LIVER FLUKE (FASCIOLOIDES MAGNA) IN ELK (CERVUS CANADENSIS) AND OTHER UNGULATES IN CANADA

Abstract

ABSTRACT:Giant liver fluke (Fascioloides magna) populations readily expand under suitable conditions. Although extirpated from the eastern slopes of the Canadian Rocky Mountains in the early 1960s, the fluke reappeared following natural spread through mountain passes from British Columbia. Herein, we assessed epizootiology of the fluke population two decades later. Between 1984 and 1991, 534 ungulates, including 381 elk (Cervus canadensis), 68 mule deer (Odocoileus hemionus hemionus), 54 white-tailed deer (Odocoileus virginianus), and 31 moose (Alces alces) from adjacent areas of Alberta (AB) and British Columbia (BC), Canada, were examined for giant liver flukes. Prevalence in elk increased from 53% to 79% in Banff National Park (BNP) in AB and 77% to 100% (1985-89) in Kootenay National Park (KNP) in BC. Super-infections (.100 flukes) were more common in later years. Generally, prevalence increased over time and with increasing age of elk. Intensity was lowest in young-of-year (BNP 865, KNP 3), but similar in yearlings (BNP 36611, KNP 2368) and adults (BNP 3365, KNP 3266). Prevalence was similar in male and female elk. Intensity was higher in males (BNP 4767, KNP 46612) than in females (BNP 2866, KNP 2264), although the maximum number of flukes (545) occurred in a female elk. Prevalence and intensity differed among other species of ungulates but patterns were similar in each park. Prevalence was lower in mule deer (BNP 6%, KNP 4%) than in white-tailed deer (BNP 44%, KNP 28%) and moose (BNP 52%, KNP 63%). Intensity differed among these species but never exceeded 30 flukes. Gravid flukes occurred only in elk and white-tailed deer. Transmission occurred primarily in late summer-fall and in wet habitats. At least seven elk died as a direct result of fluke infection. In this region, elk and white-tailed deer maintain the F. magna population with spillover into moose and, rarely, mule deer.

Genetic interrelationships of North American populations of giant liver fluke Fascioloides magna

“…In the first half of the 20 th century, wapiti were restocked from the Yellowstone National Park and expanded in number and geographic distribution within the Banff National Park (BNP). A significant exchange of wapiti between BNP and Kootenay National Park through Vermilion Pass provided a natural dispersal mechanism for F. magna from British Columbia into Alberta (see [32] and references therein).…”

Population structure and dispersal routes of an invasive parasite, Fascioloides magna, in North America and Europe

“…These localities are separated by three mountain ranges (Coastal, Columbia and Rocky Mountains) that limit the interconnection of cervids between these regions, minimizes recent genetic admixture of flukes and leads to their region-specific genetic structure. In addition, the Banff population of the parasite is a result of relatively recent dispersal of wapiti across the Rocky Mountains and its subsequent rapid expansion on their western slopes [ 42 ], which may have facilitated distinct genetic separation of flukes from the shared gene pool with NPC.…”

Fascioloides magna in Moose (Alces alces) From Elk Island National Park, Alberta

“…All livers were examined in detail as described. 23 In general, livers were sliced thinly (5 mm) and intact flukes were gently extracted and rinsed in tap water. Partial and complete flukes were staged as immature or gravid (eggs present).…”