Spatial and Temporal Patterns of Trichinella in Montana’s Black Bears, 2004-2014

Abstract

Trichinella nematodes are a globally distributed, zoonotic parasite transmitted through the consumption of infected animal tissue. Humans are at risk of contracting Trichinella by consuming undercooked bear or mountain lion meat, and thus historically, Montana Fish, Wildlife, and Parks subsidized Trichinella-testing of hunter-harvested black bears (Ursus americanus) and mountain lions (Puma concolor). Here, we summarize 11 years of data (2004-2014) on the spatial and temporal distribution of Trichinella in Montana’s black bears. Risk of infection was spatially variable, highest in northwest Regions 1 and 4, and was positively associated with black bear and grizzly bear (Ursus arctos horrobilis) densities. Prevalence has been significantly declining across the state over time from a state-wide prevalence of 0.05 in 2004 to 0.02 in 2014. Potential causes and consequences are discussed.  Montana Fish, Wildlife, and Parks stopped subsidizing Trichinella testing in 2015; hunters are asked to thoroughly cook their meat to an internal temperature of 165° F, which inactivates Trichinella species and most other parasites.