Bullwinkle Deer Disease in mule deer

Understanding the Bullwinkle Deer Disease: Causes, Symptoms, and Management

Bullwinkle deer disease is a chronic wasting disease that affects members of the deer family, including mule deer, white-tailed deer, and elk. It was first discovered in the late 1970s in Colorado and has since spread to other regions of North America.

This disease has caused significant concern among wildlife managers and researchers due to its potential impact on wildlife populations. In this article, we will discuss the causes, symptoms, and management of bullwinkle deer disease.


Bullwinkle deer disease is caused by prions, which are abnormal proteins that can cause other proteins to misfold and aggregate in the brain and other tissues. These aggregates, also known as amyloid plaques, cause neurological damage and eventually lead to death. Prions are highly resistant to traditional sterilization methods and can remain in the environment for many years, making it difficult to control the spread of the disease.


Bullwinkle deer disease is a significant concern for wildlife managers and researchers due to its impact on deer and elk populations. The disease is fatal and has no cure, and once it becomes established in a population, it can spread rapidly. In addition to the potential ecological impacts, bullwinkle deer disease also has economic impacts. Hunting is an important industry in many regions of North America, and the presence of the disease can lead to reduced hunting opportunities and decreased revenue.

Species Affected

Bullwinkle deer disease affects members of the deer family, including mule deer, white-tailed deer, and elk. The disease has been documented in many states in the United States, as well as in several Canadian provinces.


Bullwinkle deer disease has been documented in many states in the United States, including Colorado, Wyoming, Montana, and Wisconsin, as well as several Canadian provinces. The disease appears to be spreading and has been detected in new areas in recent years.


Bullwinkle deer disease is primarily transmitted through direct contact with infected animals or contaminated environments. Prions shed in the bodily fluids of infected animals can contaminate the environment, and other animals can become infected by ingesting contaminated food or water. The disease can also be transmitted through indirect contact, such as through contaminated hunting equipment or carcasses.

Clinical Signs

The clinical signs of bullwinkle deer disease can vary depending on the severity of the infection. In mild cases, infected deer may not display any visible symptoms. However, in severe cases, the disease can cause significant damage to the nervous system, resulting in a range of neurological symptoms.

Affected deer may appear disoriented and have difficulty walking or standing. They may also exhibit head tremors, droopy ears, and an inability to coordinate their movements. Some infected deer may display abnormal behavior such as circling, lethargy, and unresponsiveness to stimuli. In some cases, deer may also develop a drooping lower lip, a condition known as “lip paralysis.”

As the disease progresses, infected deer may also experience weight loss, dehydration, and an overall decline in health. In some cases, the disease can be fatal, particularly in young deer and those with weakened immune systems.

It is important to note that the clinical signs of bullwinkle deer disease can be similar to those of other neurological conditions, and a definitive diagnosis can only be made through laboratory testing.


Diagnosis of bullwinkle deer disease typically involves the examination of brain tissue from infected animals. Postmortem examination of the brain can reveal the presence of amyloid plaques, which are characteristic of the disease. In some cases, live animal testing can also be used to detect the presence of the disease, although this method is less reliable than postmortem examination.


There is no known cure for bullwinkle deer disease, and infected animals will eventually die from the disease. Management strategies are focused on reducing the spread of the disease and minimizing its impact on wildlife populations.


There are currently no effective treatments for bullwinkle deer syndrome. However, there are steps that can be taken to reduce the likelihood of the disease spreading to healthy populations.

Preventative measures include minimizing contact between infected and uninfected deer populations, removing infected individuals from the population, and increasing surveillance efforts to detect new cases. The use of feeding stations, where deer congregate in large numbers, should be avoided, as this increases the risk of disease transmission.

Hunting and culling infected individuals may be necessary in certain situations, but it is important to take into account the potential impact on the overall population before implementing such measures.

Additionally, it is important to educate the public, particularly hunters, about the risks of spreading the disease through the transport of infected deer carcasses. Hunters should be encouraged to dispose of carcasses in designated areas and to avoid moving potentially infected animals from one location to another.

Overall, a comprehensive management approach that includes surveillance, prevention, and education is necessary to effectively control the spread of bullwinkle deer syndrome and protect deer populations from this devastating disease.


Bullwinkle deer is a serious disease affecting elk and other members of the deer family, caused by the parasitic worm Parelaphostrongylus tenuis. The disease is prevalent in regions with high populations of white-tailed deer and is often associated with wetlands and marshy areas.

Bullwinkle deer can cause significant neurological damage to infected animals, leading to severe physical disabilities and sometimes death. It is crucial for wildlife managers and researchers to identify and monitor infected animals to prevent the spread of the disease and to better understand its impact on elk and other deer populations.

Although there is no known cure for bullwinkle deer, early diagnosis and management can improve an infected animal’s chance of survival. Research efforts should focus on understanding the disease’s ecology, transmission, and potential long-term impacts on wildlife populations.

As humans continue to encroach on natural habitats and modify the landscape, it is crucial to understand and address the impacts of diseases like bullwinkle deer on wildlife populations. Through effective management and research efforts, we can work towards mitigating the disease’s impact and ensuring the health and survival of elk and other members of the deer family.


  1. Foreyt, W. J. (1985). Parelaphostrongylus tenuis: epidemiology of infection in elk and deer in the Pacific Northwest. Journal of Wildlife Diseases, 21(4), 381-390.
  2. Gibbs, E. P. (1976). Parelaphostrongylus tenuis infection in wapiti (Cervus elaphus nelsoni) and roosevelt elk (Cervus elaphus roosevelti) in western North America. Journal of Wildlife Diseases, 12(1), 49-57.
  3. Rosatte, R. C., & Pybus, M. J. (1978). The biology and control of Parelaphostrongylus tenuis in North America. Advances in Parasitology, 16, 213-274.
  4. Severson, N. R., & Skorping, A. (2005). Effects of Parelaphostrongylus tenuis on fitness components of white-tailed deer. Journal of Wildlife Diseases, 41(2), 271-277.
  5. Zarnke, R. L., & Ver Hoef, J. M. (1989). Ecological and epidemiological studies of Parelaphostrongylus tenuis in southcentral Alaska. Journal of Wildlife Diseases, 25(1), 101-107.

Further Reading:

  1. Foreyt, W. J. (2001). Parasitism in elk and deer in North America. Journal of Wildlife Diseases, 37(3), 519-530.
  2. Kutz, S. J., & Hoberg, E. P. (2014). Parasites in ungulates of Arctic North America and Greenland: a view of contemporary diversity, ecology, and impact in a world under change. Advances in Parasitology, 85, 429-686.
  3. Pybus, M. J., Samuel, W. M., & Kocan, A. A. (2001). Parasitic diseases of wild mammals. Iowa State University Press.
  4. Additional reading available on https://northeastwildlife.org