Deer Disease Monitoring in Iowa

The Iowa DNR actively monitors diseases affecting deer in the state. The primary diseases that are monitored include Chronic Wasting Disease (CWD), Hemorrhagic Disease/Bluetongue (HD), and Bovine Tuberculosis (TB). The pathology and disease ecology of each have vastly different consequences for deer management.

For additional information regarding the major differences between EHD and CWD be sure to check out the chart found on the Quality Deer Management Association's website.

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Chronic Wasting Disease (CWD)

CWD is a neurological disease affecting primarily deer and elk. An abnormal protein, called a prion, attacks the brains of infected animals causing them to lose weight, display abnormal behavior and lose bodily functions. Signs of CWD in deer include excessive salivation, thirst and urination, loss of appetite, weight loss, listlessness and drooping ears and head. It is always fatal to the infected animal. Anyone seeing a deer exhibiting these symptoms should immediately contact the DNR. 

CWD can be transferred from deer to deer via direct contact and contact with bodily fluids. Therefore, prevalence and spread increase with deer density. However, abnormal protein prions that are shed from CWD positive deer can persist in the environment for many years, which can additionally infect deer. As a result, disease prevalence is also independent of deer density. There is currently no viable vaccine. Consequently, once a wild deer herd has become infected, removal is nearly impossible and increased prevalence is extremely likely. Deer management strategies generally have focused on mitigating the prevalence and spread of the disease via population reduction or some form of isolating or quarantining infected areas. Recent research in Wyoming has found that CWD has been documented to have strong population-level effects.

Population-level effect article:
Chronic Wasting Disease Drives Population Decline of White-Tailed Deer (off-site)

Testing for the CWD protein is not a food safety test. Currently it is not believed that humans can contract CWD by eating venison; however, the Center for Disease Control and Prevention recommends, when hunting in areas with CWD, strongly consider having the deer tested for CWD before you eat the meat. If your animal tests positive for CWD, do not eat that animal. For further recommendations, refer to information provided by the Centers for Disease Control and Prevention.

Under Iowa law, hunters cannot transport into the state the whole carcass of any cervid (i.e., deer, elk, moose) taken from a CWD-infected area. Only the boned-out meat, the cape, and antlers attached to a clean skull plate (from which all brain tissue has been removed) are legal to transport into Iowa. 

For the latest updates/maps available:

Hemorrhagic Disease/Bluetongue (HD)

Epizootic hemorrhagic disease and bluetongue (collectively, HD) are diseases spread by a biting midge that causes high fever in infected deer and also causes the cell walls in heart, lungs and diaphragm tissue to weaken and burst. HD cannot be transferred from deer to deer. In dry, drought years it can be worse as deer are more concentrated around water. The deer are attracted to water to combat the fever and dehydration due to the hemorrhaging. Most deer die one to four days after being infected with HD. However, the deer herd can build up an immunity to persistent strains of HD, as they have in many southern states. 

HD was widely reported in 2012 and 2013 in eastern and southern Iowa. Some losses due to HD generally occur every year, but usually at low levels and in localized areas. It is important to know that HD effects are temporary, and broad scale (County or larger) population-level effects in Iowa have historically occurred infrequently. HD effects are reduced when rain disperses the deer by providing more watering areas or a heavy frost kills the midges. Because HD is frequency dependent, reductions in deer density will not affect disease prevalence. In other words, the percent of the population that will die is only dependent on the number of infected midges that bite susceptible deer.

For the latest updates/maps available:

Bovine Tuberculosis (TB)

Tuberculosis (TB) is a bacterial disease that affects the respiratory system, and is primarily transferred through respiratory secretions between individual animals, and thus prevalence and spread are density dependent. Currently there is no evidence of TB in Iowa’s deer herd. However, TB remains an important disease to monitor because it can be transferred from livestock to deer and vice versa. Deer management strategies of localized density reduction or depopulation of target areas can be successful at removing TB.