Symptoms
Drastic weight loss (wasting or emaciation)
Drooping head and ears
Excessive salivation (drooling)
Increased drinking and urination
Loss of appetite
Lack of coordination and stumbling
Lethargy (tiredness or depression)
Blank facial expression
Teeth grinding
Changes in behavior (e.g., decreased interactions with others, wandering in circles)
Causes
CWD is caused by prions (misfolded prion proteins, designated PrPSc), which are infectious agents that trigger normal prion proteins (PrPC) in the brain to misfold. These misfolded prions accumulate, forming plaques that damage brain tissue, leading to the disease's symptoms. The exact origin of CWD prions is unknown.
Medicine Used
There is currently no cure or treatment for Chronic Wasting Disease. The disease is invariably fatal.
Is Communicable
Yes, CWD is communicable among cervids. It can spread through:
Direct contact: Animal-to-animal contact, especially through saliva, urine, feces, blood, and antler velvet.
Indirect contact: Contact with contaminated environments, such as soil, water, or plants contaminated with prions. Prions can persist in the environment for years.
Mother to Offspring: Possible vertical transmission, although not fully understood.
Precautions
Hunters: Have deer or elk tested for CWD, especially in known CWD areas, before consuming the meat. Avoid shooting, handling, or consuming animals that appear sick. Wear gloves when field dressing carcasses and minimize contact with brain and spinal tissues. Bone out the meat.
Wildlife Agencies: Monitor deer and elk populations. Implement testing programs. Control animal density in affected areas. Educate the public.
General Public: Report any sick or dead deer or elk to wildlife authorities. Avoid feeding deer or elk. Be aware of CWD distribution and follow guidelines from wildlife agencies.
Prevention of Environmental Contamination: Proper disposal of carcasses in landfills or through incineration is vital to reduce environmental contamination.
How long does an outbreak last?
CWD is not an "outbreak" in the traditional sense (like a sudden flu outbreak). It's a persistent and progressive disease in affected populations. Once CWD is established in an area, it can persist for many years, potentially indefinitely, due to the long-term environmental persistence of prions. The duration of the disease within an individual animal can be several years from initial infection to death.
How is it diagnosed?
CWD is diagnosed through laboratory testing of tissue samples. The most common methods include:
Immunohistochemistry (IHC): This method detects prions in tissue samples (typically lymph nodes, brainstem) using antibodies.
Enzyme-Linked Immunosorbent Assay (ELISA): Another antibody-based test used to detect prions in tissue or blood samples.
Real-time quaking-induced conversion (RT-QuIC): A highly sensitive test that can detect prions in various samples, including brain, lymph nodes, and even feces or saliva, by measuring the conversion of normal prion proteins to the misfolded form.
Samples are usually taken post-mortem (after death) from lymph nodes, brainstem or other nervous tissue. Live animal testing is done with rectal biopsies or tonsillar biopsies.
Timeline of Symptoms
The timeline of CWD symptoms can vary, but generally follows this pattern:
Incubation Period: This is the period between infection and the appearance of initial symptoms. It can last for over a year or even several years. During this time, the animal appears healthy but is shedding prions into the environment.
Early Stage: Subtle changes in behavior or body condition might be observed. These may be easily overlooked.
Mid-Stage: More noticeable symptoms begin to emerge, such as weight loss, increased drinking and urination, and subtle changes in gait or coordination.
Late Stage: The animal exhibits pronounced wasting, severe neurological signs (loss of coordination, stumbling), excessive salivation, drooping head, and is often lethargic and unresponsive. Death usually occurs within a few months of the onset of severe symptoms.
Important Considerations
Human Health: While there is currently no evidence that CWD can be transmitted to humans, the CDC and WHO recommend caution. Hunters should avoid consuming meat from CWD-infected animals.
Environmental Persistence: CWD prions can persist in the environment for years, making eradication extremely difficult.
Geographic Spread: CWD continues to spread to new areas, raising concerns about its long-term impact on cervid populations and ecosystems.
Economic Impact: CWD can have significant economic impacts on hunting, tourism, and wildlife management agencies.
Ongoing Research: Research is ongoing to better understand CWD transmission, develop diagnostic tools, and explore potential management strategies.