CWD and EHD in Iowa

By Katie Rising

 

Challenges posed by CWD and ED

As conservationists and hunters, we are deeply invested in the health and sustainability of our wild deer population. Our deer face significant threats from emerging and spreading diseases like Chronic Wasting Disease (CWD) and Epizootic Hemorrhagic Disease (EHD). While directly treating individual wild animals on a large scale isn’t practical, so, we should have a proactive, management to minimize the impact on our area.

History of CWD

CWD is a fatal neurological disease and is a type of transmissible spongiform encephalopathy (TSE), similar to mad cow disease. Once an animal contracts CWD, there is no vaccine or cure. It also has a long incubation period and a deer that seems healthy could in fact be infected.

CWD first emerged as a clinical “wasting” syndrome in 1967 in captive mule deer at a research facility in Fort Collins, Colorado. It wasn’t until 1978 that it was formally classified as a TSE. By the late 1970s, it was identified in captive mule deer, black-tailed deer, and elk in Colorado and Wyoming. The first wild case was an elk in Colorado in 1981, establishing an initial endemic zone.

According to the Iowa DNR, the first case in Iowa was in Allamakee County in 2013, and has spread to 29 counties. Acceleration of CWD’s spread began in the 2000s. After being initially confined to the Colorado/Wyoming wild populations, it spread to captive herds in Canada and other US states in the mid-1990s. The discovery of CWD in wild white-tailed deer in South Dakota and Nebraska in 2001 marked a critical turning point. From 2002 onward, CWD rapidly expanded its footprint, reaching states like Wisconsin, Iowa, Pennsylvania, and Texas.

As of April 2025, CWD has been detected in 36 US states in either captive or wild populations. This ongoing expansion, consistently updated by organizations like the USGS, indicates a troubling trend. While precise year-to-year prevalence rates vary, the geographical spread is undeniable, and in established areas, we are witnessing increasing infection rates within deer populations, with some localities reporting over 50% prevalence.

Our Strategies Against CWD:

Given the nature of CWD, our best practices focus on multi-faceted approaches:

Hunting is conservation and increased deer harvest, especially in CWD-affected areas, helps reduce overall deer density. Lower densities mean less direct contact between animals, and less transmission. This is why we see special “Deer Management” seasons set by the Iowa DNR. The strategy is to lower the population in confirmed CWD counties.

In the hunting community, we’ve seen some states go to a band on feeding and mineral sites. In Iowa, we can still do this (outside of seasons and along with the parameters set and enforced by the Iowa DNR). This limits the concentration of deer in high numbers, and limits direct contact of saliva, urine, and feces. Many states have rightly implemented bans and in Iowa there seems to be less mineral out in the spring than there was 10 years ago.

Testing of harvested deer, especially in known CWD areas or high-risk zones, is critical for early detection, tracking the disease’s spread. Also, the Center of Disease Control recommend testing and not consuming infected CWD deer. You can submit a sample either online, via mail, or connect with an Iowa DNR deer biologist to have someone collect a sample. To share data on CWD positives in Iowa, positive sample statistics, and surveillance from current and previous seasons, the Iowa DNR launched an interactive dashboard.

Many states have regulations on the transport of deer, elk, and other species to minimize the spread. Most require the meat to be de-boned, and the skull plate to be cleaned. Per Iowa rules and regulation, if you hunt a deer, elk, or moose in a CWD-infected area, don’t bring the whole animal back to Iowa. Iowa law only permits you to transport boned-out meat, the cape, and antlers on a cleaned skull plate (all brain tissue must be removed).

History of Epizootic Hemorrhagic Disease (EHD)

EHD is a viral disease in white-tailed deer, though it can impact other ruminants. It is caused by the epizootic hemorrhagic disease virus (EHDV) and is transmitted by biting flies, often referred to as “no-see-ums.” 

EHD was first found in white-tailed deer in New Jersey in 1955. Historically, outbreaks occurred in late summer and early fall, particularly in the southern US where midge populations thrive.

However, EHD steadily expand its range northward, affecting the Midwest, Northeast, and even parts of the Northwest. Notable outbreaks, such as the widespread event in over 30 states in 2012, and recurring annual outbreaks. In Iowa, pockets have seen outbreaks several out of the last 10 years. Outbreaks end with the first hard frost that kills off the midges.

EHD is now considered the most common viral disease affecting white-tailed deer in the US. While southern states often experience annual, mild losses, northern regions, where deer may lack immunity, can lose a high population to the spread of EHD. The distribution and severity of EHD vary greatly year to year, from scattered cases to dramatic local outbreaks.

Iowa’s Approach to EHD

Since there is no vaccine or direct treatment for EHD in wild deer, our best practices revolve around managing the midge vector and reducing deer congregation. For example, during dry spells, deer congregate at dwindling water sources, creating ideal breeding grounds for midges. Hunters and landowners are crucial for surveillance. Reporting any sick or dead deer, especially near water during late summer/early fall, helps wildlife agencies monitor outbreaks and track the disease’s impact. It’s difficult to manage pressure and scout for EHD, but if you go for a walk in the late summer, look for those dead deer. If you’ve seen a buck that was reliably visiting your food plot just “disappear” in August or September, you might go look near by and see if he is deceased. Otherwise, you might be hunting a buck that isn’t there. Also, if you find several deer dead in a small area, especially near water, this could indicate EHD in your area. According to the Iowa DNR, Deer populations typically rebound from EHD outbreaks within two to three years. 

Understanding the full scope of hemorrhagic disease in Iowa’s deer has always been a challenge due to underreporting. To address this, the Iowa DNR has launched a new reporting tool and an accompanying annual dashboard, both available on the Deer Hunting and Deer Health webpage (www.iowadnr.gov/deer). By simplifying the reporting process and improving data accuracy, these tools will significantly enhance our ability to manage Iowa’s deer populations effectively.

The challenges posed by CWD and EHD to our wild deer are substantial. There are no simple solutions. However, by practicing proactive management strategies we can work collectively to minimize their impacts.