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In the Missouri deer population, chronic wasting disease (CWD) and epizootic hemorrhagic disease (EHD) can show similar signs and symptoms. The comparison of symptoms, spread, and causes of the two diseases below can help hunters and landowners identify disease in their local population.
CWD has been found in Missouri and is slowly spreading although it remains relatively rare in the state at this time. EHD has periodically affected deer across the U.S., including in Missouri, for decades. EHD can have significant short-term impacts on the deer population, but it has never been shown to have a long-term impact on the population.
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| Chronic wasting disease | Epizootic hemorrhagic disease | |
|---|---|---|
| Cause | Misshapen proteins called “prions” concentrate in the lymph nodes and brain of infected animals and lead to a slow death. | A virus called epizootic hemorrhagic disease virus (EHDV). Different strains (subtypes) of the virus exist, with varying levels of virulence. |
| Spread | From deer to deer through body fluids. | By biting midge flies during the summer and fall until cold weather kills the flies. |
| Time to symptom onset | Can take more than 18 months for an infected deer to show symptoms. | Infected deer typically show symptoms within days of being infected. Those that die do so within weeks of being infected. |
| Symptoms | Early in the disease, deer appear normal. As the disease progresses, symptoms include excessive salivation, drooping head and/or ears, tremors, emaciation, lack of coordination, and change in behavior such as lack of fear of humans. | Fever, reduced activity, and swollen neck, tongue, and eyelids. Infected deer are often found near or in water and may appear dazed, lethargic, and nonresponsive to the approach of people. |
| Outcome | Kills all infected deer. | Does not kill all infected deer. Deer that survive develop antibodies for future immunity. |