By Adrien Bastidas ’30, Megan Morrison ’31, and Sammy Baron ’27

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Utah is a state defined by its unique landscapes. Ranging from red-rock deserts and rugged canyons to dense conifer forests and alpine peaks this state is home to some of the most iconic wildlife in the West. 

Mule deer, elk, and moose — the “King of the Forest” — are an irreplaceable part of what makes the state’s outdoors so special whether you admire these animals from a hiking trail or pursue them through Utah’s rich hunting tradition. 

Yet beneath the beauty of Utah’s great outdoors, its big game animals are facing pressures from a growing, silent threat. Emerging diseases, blood-sucking parasites, and changing environmental conditions are increasingly influencing the health, survival, and future of these species. An impact that could result in large implications for the ecosystems these animals call home.

As temperatures change and wildlife distributions shift, parasites and diseases are finding more opportunities to spread across Utah’s mountains and valleys. Researchers at Utah State University are working to understand how threats such as chronic wasting disease, arterial worms, and winter ticks are affecting Utah’s ungulates. Winter ticks have become an increasing concern for Utah’s moose, the southernmost, naturally occurring population in North America, CWD continues to expand into mule deer and elk populations across the West.

Together, these threats raise questions about what the future of cervids in Utah looks like.

“Moose in Utah pose a very unique opportunity to study how animals at the edge of their range are able to adapt in order to survive and continue expanding,” says T.J. Clark-Wolf, an assistant professor in USU’s Department of Wildland Resources and Ecology Center. “By having a clearer image of how their population is doing, we can predict what the future may look like not just in Utah but across their species’ range.”

The consequences of winter ticks are already well documented on the East Coast. In Maine and New England, infestations have caused moose calf mortality rates approaching 70% in some years. Heavily infested adults can carry more than 150,000 ticks, often leaving them with a pale appearance because the animals rub off their dark topcoat due to extreme itching. It’s a phenomenon that’s earned the animals the nickname “ghost moose” and it’s now unfolding in Utah.

Since naturally expanding into the state during the early 1900s, moose have become one of the Utah’s most recognizable wildlife species. Today, the largest population occupies the Wasatch Mountains where winter ticks can be abundant. USU researchers have been tracking the parasites’ potential impacts on the moose for over a decade.

Winter ticks are not the only major concern for moose. While this external parasite poses great risks for their health, the arterial worm is an internal parasite that’s also problematic. Spread to moose when infected deer and horse flies feed on their blood, these tiny nematodes move from the fly’s mouth to a moose’s inner skin. From there, the arterial worm circulates to the moose’s cerebral arteries where it can grow too large for the artery, causing a rupture. Consequently, moose may appear to have cloudy eyes and dead tissue around their snout and ears. In severe cases, the arterial worm can even kill its much larger host.

At Utah State, Dr. Clark-Wolf’s lab and Dr. Sarah Weinstein’s lab, as well as the Utah Division of Wildlife Resources, are working together to better understand the pressures winter ticks and warming climates put on our moose populations. 

“Knowing where and when animals like moose are most likely to encounter these parasites, and how their habitat preferences overlap with infection risk can help in developing management plans that support healthier wildlife populations,” Weinstein explains.

Graduate students Adrien Bastidas and Sammy Baron have taken on two sides of this question to dive deeper into this problem. Bastidas is hoping to identify whether moose use behavioral strategies to survive hot, parasite-rich environments by seeking high-elevation landscapes that provide cooler temperatures and potential refuge from winter ticks. Baron’s research focuses on identifying where winter ticks and arterial worms pose the greatest risk. By trapping and collecting parasites across the landscape, she is mapping areas where moose may be the most vulnerable.

Despite these pressures, Utah’s moose population has continued to slowly grow.

However, these problems are not just confined to wilderness areas. In neighborhoods where mule deer and elk often intersect, they risk spreading chronic wasting disease — a fatal neurological disease that affects cervids, including deer, elk, and moose. First identified in captive mule deer in Colorado in 1967, CWD has continued to spread and has now been documented in free-ranging populations across 34 U.S. states, four Canadian provinces, and parts of Europe. 

Often referred to as the “zombie deer disease,” CWD causes progressive degeneration of the brain, resulting in severe weight loss, abnormal behavior, loss of fear of humans, and ultimately death. This disease spreads efficiently through both direct contact between animals and indirect exposure to contaminated environments, where infectious prions can persist for years. Infected animals may carry and shed the disease for months before showing clinical signs, making surveillance and disease management particularly challenging. 

Currently, the only reliable way to diagnose CWD is by testing tissues such as lymph nodes or the brainstem after an animal has died.

The first cases of CWD in Utah were detected near Vernal and Moab in 2002. Since then, the disease has continued to expand across the state. As of February 2026, 435 mule deer and 11 elk have tested positive for CWD in Utah, with the highest prevalence in the deer population — approximately 20% — occurring in the La Sal unit. 

Beyond its effects on individual animals, CWD threatens the long-term health and sustainability of deer and elk populations, resulting in ecological, economic, and cultural consequences that cost the United States tens of millions of dollars each year. In response to the growing threat of CWD to Utah’s mule deer, Dr. Kezia Manlove’s laboratory at USU has partnered with the UDWR and the USDA National Wildlife Research Center to develop a test capable of detecting the disease in live animals.

That test detects prions — abnormal proteins that can cause fatal brain diseases — from samples such as nasal swabs and ear biopsies. While it has not yet been validated for diagnosing CWD, early results are promising and have closely matched postmortem diagnoses.

Researchers hope this work will improve our understanding of how warm winters in Utah may severely limit our moose populations by positively contributing to winter tick survival and reproduction, as well as how CWD develops and spreads. 

By enabling earlier detection of infected animals and providing wildlife managers with new tools to monitor disease spread, they can make more informed management decisions aimed at conserving healthy big game populations for the future.

“This research can help managers direct limited resources toward the places and populations where action is most likely to make a difference. It can also provide a foundation for evaluating whether those actions are improving survival and sustaining Utah’s deer, elk, and moose over time,” says Daniel Macnulty, a professor in USU’s Department of Wildland Resources.