Chronic Wasting Disease: How Wildlife Disease is Shaping Wildlife Management
May 28, 2020
In a recent NCEL blog, NCEL discussed the relationship between wildlife diseases and pandemics. These diseases, otherwise known as zoonoses, involve the transfer of germs between humans and non-human animals. They can also be spread human-to-human, as has been seen with COVID-19. Increasing public awareness of zoonoses has fostered a growing concern about the management and control of their spread. As with COVID-19, wildlife diseases, if unmanaged, can carry widespread ecological, social, and economic implications.
This blog focuses on one wildlife disease in particular, chronic wasting disease (CWD). CWD has garnered increased attention in recent years due to large scale negative impacts on the several species it infects, in addition to scientific uncertainty regarding its ability to transfer to humans.
What is Chronic Wasting Disease?
Chronic wasting disease is a fatal, contagious neurological disease that affects cervids (deer, elk, moose and caribou). It’s caused by “prions,” which are a type of protein that can cause normal proteins in the brain to fold abnormally, leading to a spongy degeneration. Prions are transmissible, and when introduced to a healthy cervid, can cause damage to that animal’s nervous system through the misfolding of the animal’s healthy proteins. According to the Chronic Wasting Disease Alliance, transmission can occur through direct animal-to-animal contact, or through contact with saliva, feces, or carcass parts of an infected animal. It’s also possible for CWD to spread through soil that has been contaminated with any of these bodily fluids. “Prion diseases” occur in humans as well, with one of the most common being Creutzfeldt-Jakob disease (CJD).
Death is inevitable for CWD-infected animals. Although it may take over a year before an infected animal displays symptoms, once symptoms are present, the disease progresses rapidly. Symptoms of this nervous system disease include drastic weight loss (wasting), stumbling, and excessive urination and salivation.
Chronic wasting disease is thought to have originated in Colorado in the 1960s, and has since been found in 26 states, as well as in some parts of Canada, Norway, and South Korea.
Connection between CWD and Human Health
To date, no cases of CWD in people have been reported. However, public health officials recommend that humans avoid contact with infected agents and refrain from consuming meat from infected animals. Diseases have the ability to mutate and adapt. Since there is no conclusive evidence establishing immunity for humans, the World Health Organization advises preventing agents of “all known prion diseases from entering the human food chain.”
In addition to the risk posed to human health, there are several other factors to consider that could impact the way policies are shaped.
- Outdoor Recreation and Game Food Sources: Hunters may become less willing to hunt in areas where CWD has been found, which could impact the amount of revenue brought in from permits.
- Ecology: The long term effects on cervid population dynamics are unknown, but if CWD continues to spread, a decrease in overall cervid numbers could have large negative impacts on plant and predator species, to which cervids are closely connected. Climate change has also impacted animals’ behavior and range, and poses the risk of driving independent herds closer together as cervids seek more suitable habitat, increasing the chance of transmission.
- Private Reserves and Feeding Stations: Artificial congregation of cervids, through agency feeding of free-roaming wildlife or in private hunting reserves, poses a high risk of spreading CWD and other wildlife diseases. This means that supplemental feeding practices may need to be reexamined.
- Traditional Foods: In Canada, deer, elk, and moose are considered traditional foods, and are relied upon by many Indigenous communities. In the U.S., this is also true for Native American communities who might be negatively impacted by CWD outbreaks due to a reliance on traditional foods.
While there is currently no vaccine capable of preventing CWD infection, there are many wildlife management policy options to help limit the spread of this disease. In 2017, Congress introduced the Chronic Wasting Disease Management Act (HR 4454) which was designed to provide additional funding for CWD research and management efforts. In addition to this federal effort, many states are developing their own management efforts because of the unique challenges that CWD poses in the variety of locations in which it has been found.
For example, Mississippi recently introduced a bill that would require CWD testing of white-tailed deer harvested within any enclosure. In recognition of the high costs related to wildlife disease management, Minnesota also recently introduced legislation (HF 3591) that would appropriate funding for the study of CWD.
Other relevant legislation includes:
- New Jersey A. 949: If passed, would prohibit the possession of deer or elk originating from outside the state.
- Alabama HB 369: If passed, would authorize the Department of Agriculture and Industries to make payments for indemnity for the purchase and destruction of captive cervids that are infected with CWD or otherwise exposed to CWD, to augment the existing federal program.
- Montana passed a bill (SJ. 9) in 2017 that created an interim committee to study CWD impacts and strategies for its control.
Management options are not limited to legislation. The Western Association of Fish and Wildlife Agencies (WAFWA) developed the Recommendations for Adaptive Management of Chronic Wasting Disease in the West which include three primary strategies to reduce prevalence and transmission:
- Reduce artificial points of host concentration such as feedlots
- Adjust hunting regulations with bias toward male animals
- Selectively remove animals in concentrated areas where CWD is known to occur
These options are mainly for wildlife management agencies and can be supported through funding introduced through legislation. An adaptive management approach is essential because diseases and animal behavior are changing due to climate change.
As research continues to help develop a collective understanding of chronic wasting disease, more policy measures will likely become opportune and necessary. In addition to state legislation and action taken by wildlife management agencies, other opportunities for control of the spread of CWD exist in developing relationships with private landowners, who might be able to help with testing efforts.
While gaps still exist in CWD research and data, wildlife diseases like chronic wasting disease are likely manageable through effective monitoring, control and supporting legislation, and large-scale outbreaks may be potentially preventable.