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Deer Health in Iowa

Iowa is nationally renowned for its wild white-tailed deer, and that’s largely a reflection of habitat quality at the nexus of agricultural fields, woodlands, and riparian corridors. The Iowa Department of Natural Resources routinely monitors health events affecting our native wildlife. Ailments affecting deer in Iowa are listed below, categorized by the severity of their impacts. Incidental health issues may impact one or a few deer locally but are of minor consequence to the larger population. Seasonal diseases may have severe local impacts while their intermittent nature allows populations to rebound. Endemic diseases may have small impacts today but can cause devastating impacts long-term as they increase in prevalence (proportion infected) and geographic spread. Accordingly, Chronic Wasting Disease poses the greatest threat to the health and continuity of Iowa’s deer herd.

Fibromas
These are proliferative growths caused by infection with papilloma- or poxviruses, largely spread by biting insects. Fibromas tend to be darkly pigmented and relatively hairless, and because they are restricted to the skin, have no impact on meat quality.

Abscesses
Sparring is part of the normal behavioral ecology of deer, and with it penetrating wounds which can lead to abscesses. An abscess is a fluid-filled pocket containing purulent material, or pus. Pus is largely made up of dead white-blood cells, which the immune system mobilizes to fight off infection.  Abscesses can form following injury to the muscle. It is also not uncommon to find lung abscesses while field dressing, indicative of respiratory disease. These may appear as fibrous adhesions (e.g. scar tissue) connecting the lungs to the rib cage or heart once active infection has resolved. Occasionally bucks will sustain wounds to the head leading to brain abscesses. Ruminants like deer are great at walling off infections, so trimming away affected tissue and minimizing contamination  can preserve meat quality.

Foot rot/club foot
As in domestic ruminants, this disease process is often caused by bacterial invasion with Fusobacterium sp. following a penetrating injury to the interdigital space. Infection causes pain and lameness, and in extreme cases, persistent swelling can lead to a club-like appearance of the hoof or lower limb even after infection has resolved. Environmental conditions and contamination of shared paths can facilitate local outbreaks.

Hemorrhagic Disease
This term describes disease caused by two closely related orbiviruses: Bluetongue (BT) and Epizootic Hemorrhagic Disease (EHD). Though deer can contract BT, it is primarily a disease of small ruminants and cattle. In contrast, deer are the primary hosts of EHD. These viruses are spread by female Culicoides midges, often called “no-see-ums,” that consume a blood-meal from an infected deer and then transmit the virus to new hosts with each bite. Infected deer experience an incubation period of 7-10 days, during which they remain asymptomatic, followed by the rapid onset of clinical signs and death within 8-36 hours. Deer will often be found in or near bodies of water to cool themselves during end-stage disease. Occasionally, deer may survive acute disease and suffer from chronic injuries to the hoof wall (laminitis), causing deer to tip-toe or even walk on their “knees” and brisket.

Hemorrhagic disease tends to affect deer in Iowa between late summer and early fall, though outbreak severity can vary from year to year. Hunters and landowners may discover multiple deer carcasses on a property, specifically near a water source, during these months as a result of hemorrhagic disease. There is no effective treatment or known prevention for wild deer. It is important to keep in mind that these diseases typically don't impact county deer populations uniformly, meaning that deer on one property may experience a severe outbreak while deer on neighboring properties do not. Since Iowa's first major outbreak in 2012, the majority of counties that faced severe hemorrhagic disease activity saw deer populations return to normal within 2-3 years without management intervention (reduction of antlerless quotas, etc.). Counties with low or declining deer populations may be exceptions to this rule, in which case the DNR may explore options to help facilitate a recovery.

Hunters and landowners that suspect hemorrhagic disease-related deer mortalities are encouraged to report their observations using the EHD/Bluetongue Reporting Tool. Reporting this information leads to a better understanding of where and how these diseases are affecting Iowa's deer population. To see a dashboard of the annual reports, view the Annual EHD/Bluetongue Status Dashboard.

Chronic Wasting Disease
Chronic Wasting Disease (CWD) can affect wild and captive cervids (deer, elk, moose, and caribou) in Iowa and is transmitted by a misfolded prion protein shed in saliva, nasal secretions, and other excreta. Prions are normal host proteins found throughout the body, however exposure to the infectious form can force a conformational shift that causes prions to aggregate in the brain. Prion diseases are uniformly fatal and pose a grave risk to long-term herd health in populations afflicted by this disease. Learn how you can help stop the spread of Chronic Wasting Disease (CWD).