Prevalence of Trichinella spp. in Black Bears, Grizzly Bears, and Wolves in the Dehcho Region, Northwest Territories, Canada, Including the First Report of T. nativa in a Grizzly Bear from Canada

Abstract

ABSTRACT:Samples of muscle from 120 black bears (Ursus americanus), 11 grizzly bears (Ursus arctos), and 27 wolves (Canis lupus) collected in the Dehcho Region of the Northwest Territories from 2001 to 2010 were examined for the presence of Trichinella spp. larvae using a pepsin-HCl digestion assay. Trichinella spp. larvae were found in eight of 11 (73%) grizzly bears, 14 of 27 (52%) wolves, and seven of 120 (5.8%) black bears. The average age of positive grizzly bears, black bears, and wolves was 13.5, 9.9, and approximately 4 yr, respectively. Larvae from 11 wolves, six black bears, and seven grizzly bears were genotyped. Six wolves were infected with T. nativa and five with Trichinella T6, four black bears were infected with T. nativa and two with Trichinella T6, and all seven grizzly bears were infected with Trichinella T6 and one of them had a coinfection with T. nativa. This is the first report of T. nativa in a grizzly bear from Canada. Bears have been linked to trichinellosis outbreaks in humans in Canada, and black bears are a subsistence food source for residents of the Dehcho region. In order to assess food safety risk it is important to monitor the prevalence of Trichinella spp. in both species of bear and their cohabiting mammalian food sources.

High Prevalence and Intensity of Trichinella Infection in Yukon American Black (Ursus americanus) and Grizzly (Ursus arctos) Bears

“…Our estimate of a mean 35 LPG for grizzly bears is also the highest of all reported studies in North America. We did not find a significant relationship between age and LPG in either species, similar to the results of Larter et al (2011), although we did find a trend toward younger bears of both species having higher larval burdens than older bears. Younger animals in a population might have higher parasite burdens because of induction of less effective specific immunity during initial infection, compared with re-exposure or superinfection, or lower innate resistance to infection (Davies et al 2008).…”

“…The highest recorded prevalence is 12% in the Kootenay region of British Columbia (Schmitt et al 1978). In the Northwest Territories, Larter et al (2011) and Johnson et al (2013) report a prevalence of 5.8%. Our 20% prevalence in black bears was the highest reported in Canada, although our sample size is small.…”

“…Yukon bear samples yielded only the coldtolerant Trichinella T6 genotype (Gajadhar and Forbes 2010). Larter et al (2011) reported both T6 and Trichinella nativa in both black and grizzly bears in Northwest Territories. Although T. nativa has been described as the most cold hardy Trichinella species, T6 may survive for years at between À6 C and À20 C. Yukon winter temperatures are often colder than À20 C, but temperatures under the snowpack normally fall within the temperature range enabling long-term survival of T6 L1 (Pozio 2016).…”

Could the re-emerging practice of wild boar hunting linked to the recent economic crisis lead to new outbreaks of trichinellosis in Lebanon?

“…Studies, however, have shown that not all species of Trichinella are sensitive to cold temperatures. In fact, T. spiralis larval worms are neutralized by freezing the pork either 20 days at À15 °C or 3 days at À20 °C [10,12,29]. In contrast, other species found in wild boars, such as T. britovi and T. nativa, are able to resist cold temperatures [10,12,21,29].…”

“…In fact, T. spiralis larval worms are neutralized by freezing the pork either 20 days at À15 °C or 3 days at À20 °C [10,12,29]. In contrast, other species found in wild boars, such as T. britovi and T. nativa, are able to resist cold temperatures [10,12,21,29]. To kill the encysted larvae, internal meat temperatures must reach 62 °C or more, taking into consideration the variability in heat distribution and cooking techniques [6].…”