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Deer Health - Disease
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CWD:
Chronic Wasting Disease (CWD) was first detected in Wisconsin in 2002. Since then sampling had been conducted every year in various places throughout the state.
Total # Sampled Deer Graph
The top graph on this page represents the number of deer that have been sampled for CWD per year as well as the number of CWD positive results.
Sick Deer Tested for CWD Graph
Landowners and citizens are encouraged to contact the department when a deer showing clinical signs is seen. If possible these deer are dispatched and sampled for CWD.
More information about CWD in Wisconsin can be found on the department website.
For additional Information….
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Non-CWD:
This fall epizootic hemorrhagic disease virus EHDV was detected white-tailed deer in seven counties in southwestern Wisconsin from August through October. The outbreak was centered in Crawford County with approximately 226 deer reported to the Department that were suspected or confirmed to have died from the virus. Other counties in the affected area included Vernon (42 reported), Grant (23 reported), Richland (10 reported), Sauk (17 reported), La Crosse (10 reported) and Iowa (one reported).
EHD History
Epizootic hemorrhagic disease (EHD) is an acute, infectious, viral disease spread by biting insects (especially midges) that affects white-tailed deer and some other hoofed animals. In white-tailed deer the severity of the disease depends upon the deer’s previous exposure to the virus and strain of the virus. At this time, it does not appear that EHD is endemic (always found) in Wisconsin which means that when the virus does appear here, it is more likely to be fatal to deer.
Prior to 2019, the last confirmed outbreak of EHD in Wisconsin occurred in 2012. During the late summer and early fall of 2012, 427 deer found dead from eight southern Wisconsin counties tested positive or were identified as probable or suspect of dying from EHD. In addition, during the late summer and early fall of 2015, reports of approximately 80 dead deer were received from across Columbia, Marquette, and Sauk counties. Carcasses were found too decomposed to be useful to test for EHD so it is undetermined whether any of these deaths were due to EHD.
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Non-CWD:
This fall epizootic hemorrhagic disease virus EHDV was detected white-tailed deer in seven counties in southwestern Wisconsin from August through October. The outbreak was centered in Crawford County with approximately 226 deer reported to the Department that were suspected or confirmed to have died from the virus. Other counties in the affected area included Vernon (42 reported), Grant (23 reported), Richland (10 reported), Sauk (17 reported), La Crosse (10 reported) and Iowa (one reported).
EHD History
Epizootic hemorrhagic disease (EHD) is an acute, infectious, viral disease spread by biting insects (especially midges) that affects white-tailed deer and some other hoofed animals. In white-tailed deer the severity of the disease depends upon the deer’s previous exposure to the virus and strain of the virus. At this time, it does not appear that EHD is endemic (always found) in Wisconsin which means that when the virus does appear here, it is more likely to be fatal to deer.
Prior to 2019, the last confirmed outbreak of EHD in Wisconsin occurred in 2012. During the late summer and early fall of 2012, 427 deer found dead from eight southern Wisconsin counties tested positive or were identified as probable or suspect of dying from EHD. In addition, during the late summer and early fall of 2015, reports of approximately 80 dead deer were received from across Columbia, Marquette, and Sauk counties. Carcasses were found too decomposed to be useful to test for EHD so it is undetermined whether any of these deaths were due to EHD.
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Chronic Wasting Disease (CWD) is a fatal, contagious neurological disease known to infect white-tailed deer, mule deer, elk and moose. It causes a characteristic spongy degeneration of the brains of infected animals resulting in emaciation, abnormal behavior, loss of bodily functions and ultimately death. CWD belongs to a group of diseases known as transmissible spongiform encephalopathies (TSEs). Other TSEs include scrapie in sheep, bovine spongiform encephalopathy (BSE, also called “mad cow disease”) in cattle, transmissible mink encephalopathy in farmed mink, and Creutzfeld-Jakob disease in humans.
CWD was first detected in Wisconsin in 2002 when three deer taken by hunters near the village of Mount Horeb, about 10 miles southwest of Madison, tested positive. Since that time an intensive surveillance effort has been undertaken to better understand the geographic distribution of the disease, the prevalence of the disease where it occurs and changes in the prevalence over time.
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Collection and analysis methods
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Sampling stations were set up at previous registration stations which allowed for the collection of biological samples for CWD testing. Age, sex and kill location (deer management unit, county and Public Land Survey System [PLSS] township/section) are collected from harvested deer. Retro-pharyngeal lymph nodes are collected for CWD testing by the Wisconsin Veterinary Diagnostic Laboratory.
Statewide disease detection surveillance efforts took place in 2002-2003, and again in 2005-2008. Permanent monitoring areas were established around the centers of disease foci in southwestern (SW Core Area) and southeastern (SE Monitoring Area) Wisconsin where annual efforts were made to test the majority of harvested deer > 1.5 years old. Less intensive monitoring was conducted elsewhere in southern Wisconsin in the area formerly known as the CWD Management Zone as well as other areas of the state where positives have been found in the wild herd or captive facilities.
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The graphs on this page show the number of deer tested and the number positive for CWD per year. A subset of these sampled deer are sick deer that were showing clinical signs for CWD. Often these deer are reported to the department by a landowner or citizen in the area. The landowner may get permission to dispatch the deer if the deer can be put down safely or a department employee will put the deer down. The deer is then tested for CWD.
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Limitations and precautions
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Limited statewide CWD program funding precludes sampling everywhere each year. Because sample sizes are limited, estimation of the geographic distribution of disease requires pooling data over multiple years. Likewise, estimation of changes in time require combining data over multiple areas (e.g., townships).
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It will be important to develop ways to cost-effectively assess CWD prevalence and geographic distribution with limitations in budgets and resources.
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Additional background materials related to this metric
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Additional information on deer health can be found on the department website.
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