Chronic Wasting Disease in Wild Deer in Iowa: Surveillance and Results for the 2024-2025 Season. The Iowa Department of Natural Resources (DNR) detected the disease in 134 deer across the state over the 2024 surveillance season (April 1, 2024-March 31, 2025). MAP COURTESY OF IOWA DNR

TAMA COUNTY – Chronic Wasting Disease (CWD) and Epizootic Hemorrhagic Disease (EHD) continue to impact Iowa’s deer population, prompting ongoing surveillance and management efforts by the Iowa Department of Natural Resources (DNR). Experts, including Catherine Cummings (Iowa State University Extension and Outreach Chronic Wasting Disease Specialist), emphasize the importance of monitoring and reporting cases to help make informed decisions regarding deer management and disease control.

Chronic Wasting Disease (CWD): An Ongoing Concern

CWD is a 100% fatal neurodegenerative disease affecting deer, elk, and moose. It is caused by misfolded prions, with no known treatment or cure. Infected deer can carry and spread the disease for 18 to 36 months before showing clinical signs, at which point they rapidly deteriorate and die. The first detection in Iowa occurred in 2013 in Allamakee County. Nationally, the first captive case was recorded in Colorado in 1967, while the first wild case was identified in Colorado in 1981 in elk.

Currently, CWD has been detected in 36 states and several other countries, including Canada, Finland, Norway, South Korea, and Sweden. Surveillance in Iowa began in 2002, and to date, 519 CWD-positive cases have been confirmed in 30 counties. Marshall County has emerged as the newest hotspot. The DNR tests between 5,000 and 6,000 deer annually, which represents about 5% of annual harvest. In the most recent testing cycle, 132 deer tested positive, with two additional suspect cases pending confirmation. Older bucks are more likely to have CWD due to increased interaction with other deer. The disease spreads through direct and indirect contact, including exposure to bodily fluids and contaminated environments.

Catherine Cummings, who recently spoke on the subject during an event hosted by Tama County Extension Services, highlighted the need for public involvement in disease management.

Catherine Cummings, back right, presents during a chronic wasting disease educational workshop held in Toledo at the Extension office on Feb. 22. PHOTO COURTESY OF HALEY PRINCEHOUSE

“Providing lymph node samples from harvested deer is a key part of the DNR’s CWD surveillance program, which helps determine the disease’s distribution and prevalence in Iowa’s deer population,” she said. “CWD sampling gives hunters and their families valuable information to make informed consumption decisions. While there have been no confirmed cases of CWD transmission to humans, ongoing surveillance remains critical to understanding and managing the disease.”

CWD Management and Hunter Participation

The CDC states that there is no evidence of CWD transmission to humans but advises against consuming meat from CWD-positive deer. The only way to confirm infection is through diagnostic testing. The testing process involves sample collection by DNR staff, which is then sent to Iowa State University’s lab. Results typically take about one week, but during peak hunting season (Gun 1), the wait can extend up to four weeks. Hunters can submit samples for $25, but DNR testing is free until quotas are met.

Upon detection of CWD in a county, the DNR’s response plan includes increased surveillance, population assessments, and management proposals. The public can assist in managing the disease by responsibly managing deer populations, avoiding artificial congregation sites such as feeders and mineral blocks, submitting deer for testing, and properly disposing of carcasses. Ideally, carcasses should be left near the harvest site or disposed of in a landfill where permitted.

Epizootic Hemorrhagic Disease (EHD) and Bluetongue

A member of Tama Turtles – Tama County’s WHEP (Wildlife Habitat Education Program) team – connects with Catherine Cummings, right, to gather advice about future careers and college opportunities related to conservation during Cummings’ presentation in Toledo on Feb. 22. PHOTO COURTESY OF HALEY PRINCEHOUSE

EHD and Bluetongue are viral diseases spread by biting midges (no-see-ums). Disease activity occurs from late summer through early fall until a hard frost occurs. Unlike CWD, EHD is often, but not always, fatal. Symptoms typically appear 7 to 10 days after exposure, and infected deer are commonly found dead near water sources as they attempt to cool down from fever. The first detection in North America dates back to the 1890s, while Iowa’s most severe outbreak occurred in 2012.

More recently, the number of EHD cases in Tama County have varied in severity, with three carcasses being reported in 2012, eight carcasses being reported in 2019, and 75 carcasses being reported in 2024.

The effects of EHD on populations vary. While it can be devastating locally, it rarely impacts entire counties. Outbreak severity often depends on drought conditions, as fewer water sources lead to increased midge activity. Deer that recover from EHD may develop cracked or sloughed hooves, which serve as a sign of past infection. The DNR relies on hunters and landowners to report suspected cases of EHD and Bluetongue to make management decisions. Hunters and landowners can report any carcasses found through the toolbox on the GoOutdoorsIA app or on the DNR’s deer health webpage.

Key Differences Between CWD and EHD

CWD is caused by misfolded prions, whereas EHD is a viral disease transmitted by midges. CWD is always fatal, while EHD can sometimes be survived. Transmission also differs, with CWD spreading through direct and indirect contact, while EHD requires a vector. The incubation period for CWD is much longer, lasting 18 to 36 months, compared to EHD’s rapid onset within seven to 10 days. While CWD requires long-term monitoring and poses a significant management challenge, EHD outbreaks tend to be seasonal, and some level of immunity can develop over time. The CDC strongly advises against consuming CWD-positive meat, whereas EHD does not impact muscle tissues, making consumption a personal choice.

Looking Ahead

While EHD outbreaks are seasonal and can diminish over time due to developing immunity, CWD poses a long-term challenge with no clear solution. Continued research, testing, and public cooperation remain crucial to managing these diseases in Iowa’s deer populations.

Hunters and residents can report deer showing signs of EHD or CWD using the online reporting tool or the Go Outdoors Iowa app. With increased awareness and proactive measures, conservation efforts can help protect the health of Iowa’s deer herds.

Cummings highlighted what we could expect and the need for public involvement in disease management:

“As we continue to detect more cases of CWD, the disease poses the greatest long-term threat to our deer population. With continued surveillance, proactive management, and cooperation with staff, we can slow its spread. Hunters and the public can play a crucial role by submitting samples, reporting sick deer, and following response carcass disposal guidelines. Please continue to report any deer that you suspect died from EHD or Bluetongue in our county–we rely heavily on these reports to understand how hemorrhagic diseases are impacting our county populations. Protecting our deer population is a shared responsibility, and by working together, we can ensure a healthy future for Iowa’s wildlife and hunting traditions.”

For the latest updates, visit https://www.iowadnr.gov/programs-services/iowas-wildlife/wildlife-disease-management.