EHD vs. CWD: Understanding the Differences and Impacts on Deer Populations

As someone who’s spent over a decade exploring and writing about the American outdoors, I’ve seen firsthand the growing concern surrounding deer health. Two diseases, Epizootic Hemorrhagic Disease (EHD) and Chronic Wasting Disease (CWD), frequently cause worry among hunters, landowners, and anyone who enjoys observing deer. Understanding the difference between ehd vs cwd, and the implications of each, is crucial for responsible outdoor recreation and wildlife conservation. This article will break down the key distinctions between deer ehd vs cwd, discuss current testing results in states like Illinois and Wisconsin, and provide resources for staying informed.

What is Epizootic Hemorrhagic Disease (EHD)?

EHD is a viral disease that affects white-tailed deer, mule deer, elk, and other members of the deer family. It’s transmitted by biting midges (small flies) of the Culicoides species. EHD outbreaks are most common during hot, dry summers and early falls when midge populations are high. The disease isn’t directly contagious between deer, meaning deer don’t spread it to each other through contact. Instead, it relies on the insect vector.

Symptoms of EHD in Deer

Recognizing the symptoms of EHD is important, especially if you spend a lot of time in deer country. Symptoms can vary, but commonly include:

• Fever
• Loss of appetite
• Weakness
• Excessive thirst and urination
• Swelling of the head, face, tongue, and eyes
• Hemorrhaging (bleeding) – often visible as blue discoloration of the tongue
• Difficulty breathing
• Sudden death

Often, the first sign observers notice is dead deer near water sources, as affected animals seek relief from their fever. The mortality rate can be significant during outbreaks, but EHD outbreaks are typically localized and don’t cause long-term population declines.

EHD Geographic Distribution and Recent Outbreaks

EHD has been reported in the eastern and central United States. Outbreaks are cyclical, with periods of high incidence followed by years with few or no cases. The USDA Animal and Plant Health Inspection Service (APHIS) provides updated information on EHD outbreaks across the country. Recent outbreaks have been reported in states like Illinois, Indiana, and Ohio. The severity of outbreaks can vary depending on weather conditions and midge populations.

What is Chronic Wasting Disease (CWD)?

Unlike EHD, CWD vs ehd represents a far more serious and persistent threat. CWD is a fatal, neurological disease affecting deer, elk, moose, and reindeer. It’s caused by misfolded proteins called prions, which accumulate in the brain and other tissues. CWD is contagious – deer can spread it directly to each other through saliva, urine, feces, and even contaminated environments. This makes it much harder to control than EHD.

Symptoms of CWD in Deer

CWD symptoms develop slowly, often over a period of months or even years. This makes early detection difficult. Common signs include:

• Weight loss
• Changes in behavior (e.g., increased nervousness, aggression, or lack of fear of humans)
• Excessive drooling
• Difficulty walking
• Loss of coordination
• Grinding teeth
• Swollen lymph nodes

Because the symptoms are subtle and develop slowly, CWD is often only detected through testing of harvested animals.

CWD Geographic Distribution and Testing Results

CWD was first identified in captive deer in Colorado in 1967. Since then, it has spread to at least 31 states, including several in the Midwest. The National Park Service is actively monitoring CWD in national parks and working with state wildlife agencies to manage the disease.

Illinois CWD Test Results

Illinois has been actively monitoring for CWD since 2002. The Illinois Department of Natural Resources (IDNR) publishes regular updates on CWD testing results. As of late 2023, CWD has been detected in several counties in northern Illinois, and the IDNR has implemented mandatory testing requirements for deer harvested in those areas. They also have established surveillance areas with specific regulations to limit the spread of the disease.

Wisconsin CWD Test Results

Wisconsin has also been heavily impacted by CWD. The Wisconsin Department of Natural Resources (DNR) provides detailed information on CWD distribution and testing results. Wi cwd test results show the disease is present in several counties, particularly in the southern part of the state. Wisconsin has implemented a multi-faceted approach to CWD management, including mandatory testing, herd reduction efforts, and restrictions on feeding deer.

Key Differences: EHD vs. CWD – A Comparison

Here’s a table summarizing the key differences between EHD and CWD:

Feature	EHD	CWD
Cause	Virus	Prions (misfolded proteins)
Transmission	Biting midges	Direct contact, contaminated environment
Speed of Onset	Rapid (days to weeks)	Slow (months to years)
Fatality Rate	High during outbreaks, but localized	100%
Contagious?	No (not between deer)	Yes
Long-Term Impact	Typically limited	Significant population declines, potential ecosystem effects

What Can You Do?

As an outdoor enthusiast, you play a vital role in helping to manage these diseases. Here are some steps you can take:

• Report Sick or Dead Deer: If you observe a deer exhibiting symptoms of EHD or CWD, or find a dead deer, report it to your state’s wildlife agency.
• Participate in CWD Surveillance: If you harvest a deer in a CWD-affected area, submit a sample for testing. This is often mandatory, but even if it isn’t, it’s a valuable contribution.
• Follow Regulations: Adhere to all regulations related to CWD management, including restrictions on feeding deer and transporting carcasses.
• Practice Proper Hygiene: When field dressing a deer, wear gloves, minimize handling of brain and spinal tissues, and thoroughly disinfect your equipment. The Leave No Trace Center for Outdoor Ethics offers guidance on responsible wildlife viewing and minimizing impact.
• Stay Informed: Regularly check with your state’s wildlife agency for updates on EHD and CWD outbreaks and management strategies.

The Importance of Responsible Outdoor Practices

The health of our deer populations is essential for healthy ecosystems and sustainable hunting opportunities. Understanding the differences between ehd vs cwd, and taking proactive steps to prevent the spread of these diseases, is a responsibility we all share. By staying informed and following best practices, we can help ensure that future generations can enjoy the beauty and abundance of our natural resources. For more information on wildlife disease management, I recommend exploring resources from the USDA Forest Service and REI Expert Advice on wildlife safety.

Disclaimer: I am not a veterinarian or wildlife biologist. This article is intended for informational purposes only and should not be considered a substitute for professional advice. Always consult with your state’s wildlife agency for the most up-to-date information and regulations.