Understanding Chronic Wasting Disease
Chronic wasting disease (CWD) is a fatal neurological illness occurring in North American deer, elk and moose populations. Also known as "zombie deer disease," it causes drastic weight loss leading to death. With CWD impacting wildlife in as many as 32 U.S. states and appearing more prevalently, understanding and controlling its spread is important to conservation efforts.
Key Characteristics of CWD
CWD has a long incubation period before symptoms appear, including:
- Emaciation and weight loss
- Listlessness and lowered head
- Excessive salivation
- Loss of urinary and bowel control
- Isolation from the herd
It is caused by prions - misfolded proteins that infect the brain and spinal tissue. Transmission occurs from animal to animal via saliva, urine and feces. Prions can bind to plants and soil and remain infectious for years.
Scope of the Spread
Since initially documented in Colorado and Wyoming in the late 1960s, CWD spread has increased substantially in North America in recent decades. Likely 10-15% of deer populations are impacted in endemic areas.
As of 2023, 32 U.S. states have wild, noncaptive deer, elk or moose that have tested positive. Most recently, Michigan, Vermont, Wyoming, Tennessee and Iowa reported new cases. Many states have emergent epidemic growth, leaving experts concerned.
Preventing Further Spread
While eradicating CWD is unrealistic given how entrenched it has become in landscapes, implementation of deer management strategies can help slow additional geographic spread and lower prevalence rates.
Culling and Testing
Selective culling of male deer showing clinical symptoms can reduce prevalence since bucks disperse CWD readily during breeding season. Lowering overall deer density also limits spread. Testing programs provide data to guide management.
Hunter Education
In endemic areas, educating hunters on carcass transportation regulations, use of commercial processors, and safe venison handling protects other deer populations. Safe field dressing and processing also reduces human exposure risk.
Feeding Bans
Banning recreational and commercial feeding avoids concentrating deer in ways that accelerate CWD transmission. Many CWD endemic states have enacted bans but compliance remains variable.
Fencing
Installing perimeter fencing around emerging outbreak sites can isolate infected populations. New Mexico saw positive outcomes from this method containing CWD's spread to mule deer and elk populations.
Researching Human Health Risks
While experts agree consuming infected venison is inadvisable, data limitations exist around the zoonotic risk from CWD exposure. Active areas of scientific inquiry include:
Species Barrier Strength
The "species barrier" makes cross-species prion transmission more difficult. But abnormal human prion illnesses do occur, including Kuru, variant Creutzfeldt-Jakob Disease and others. Researchers continue evaluating cervid-human barrier susceptibility.
Possible Transmission Routes
Ingestion of infected meat, organ transplants and blood transfusions represent theoretical human transmission routes. But the role of environmental prion exposure is unclear, especially since prions have been isolated binding tightly to plants.
Human Population Monitoring
Limited pathology testing occurs in suspected clinical human prion disease cases to identify if deer prions are involved. But not all CWD-endemic population centers can conduct these analyses regularly, hampering surveillance efforts.
Key Takeaways
Managing the accelerating spread of chronic wasting disease in North American deer remains imperative. While unlikely to eradicate CWD now, cooperative disease mitigation approaches can lower prevalence and slow new geographic emergence.
Continuing scientific research around the threat CWD also may pose to human health means all opportunities to understand and respond to this wildlife epidemic must not be wasted.
FAQs
Can humans get CWD from eating infected deer meat?
While human transmission has not been confirmed, experts recommend avoiding consumption of meat from animals known to have CWD. The CDC advises having game tested before eating.
How can you tell if a deer is infected with CWD?
In early stages, infected deer show no symptoms. Later signs include extreme weight loss, stumbling, lack of coordination, excess salivation, and lack of fear of people and predators.
Is chronic wasting disease the same as mad cow disease?
CWD and mad cow disease (BSE) both belong to the group of illnesses called prion diseases. Both involve prions causing neurological damage, resulting in death. But they are distinct prion strains capable of infecting different species.
Where did chronic wasting disease originate?
The earliest known cases of CWD occurred in Colorado and Wyoming in 1967 in captive mule deer populations. Scientists still don't know the original cause but spread likely started from captive to wild herds.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.
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