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 (i.e., study of disease) and disease ecology (i.e., population effect of disease) of each have vastly different consequences for deer management.
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 (i.e., % infected) and spread increase with deer density (i.e., density dependent). However, abnormal protein prions that are shed from CWD positive deer can persist in the environment for many years, which can also infect deer. As a result, disease prevalence is also independent of deer density (i.e., frequency dependent). In addition, there is currently no viable vaccine. Consequently, once a wild deer herd has become infected, removal is nearly impossible and increased prevalence in 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 limiting growth.

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 the World Health Organization recommend hunters avoid eating meat, brain, eyeballs, or spinal cord of infected deer, and that hunters wear protective gloves while field dressing game.

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. 

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 their heart, lungs and diaphragm to weaken and burst. HD cannot be transferred among deer. Thus prevalence of HD is frequency dependent (i.e., not related to deer density). 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 will build up a genetic 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 (about once every 5 years). 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.

Bovine Tuberculosis (TB)

Tuberculosis (TB) is a bacterial disease that affects the respiratory system, and is primarily transferred through respiratory secretions between deer, 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.

For the latest updates/maps available on HD and CWD: