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Doing your Part in the Management of Iowa's White-tailed Deer and the CWD Threat

White-tailed deer are as synonymous with the ‘acreage living’ experience as fences and ragweed. We find them everywhere in Iowa, thriving in urban forests and remote sections of cropland with little more than a ditch for cover. To many of us they’re a welcome sight, a glimpse of life on a cold winter day or an opportunity to spend time afield with family and friends each fall in their pursuit. To some they’re an annoyance, pestering crops or landscape plants with their seemingly insatiable drive for fresh plant growth and woody browse. Love them or hate them, one thing is clear: despite their tumultuous experience in Iowa’s earliest years of statehood, white-tailed deer are here to stay and participation in their management and conservation is a core responsibility of all property owners. And today, new challenges like that posed by Chronic Wasting Disease are elevating those responsibilities and require wide engagement in ensuring deer continue to thrive in Iowa....

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Iowa's Wildlife

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Chronic wasting disease

Chronic Wasting Disease in Deer

https://store.extension.iastate.edu/product/Chronic-Wasting-Disease-in-Deer

Chronic wasting disease, or CWD, is a neurological disease infecting wild white-tailed deer in Iowa and throughout North America. This article reviews the most relevant and up-to-date scientific information about the disease and provides recommendations for addressing this emerging challenge in Iowa. Learn more about CWD from this video:

Chronic Wasting Disease Ambassadors

Chronic Wasting Disease Ambassadors is an education program from Iowa State University Extension and Outreach that seeks to train concerned citizens, hunters, and community leaders to be good ambassadors and lead community responses to the management of Chronic Wasting Disease in white-tailed deer in Iowa.

Bats in Iowa

Nine species of bats are found regularly in Iowa’s fields and forests. All of these bat species are aerial insectivores, using their skilled echolocation to hone in on flying insects in forests, fields, and over water. Bats are thus an extremely important part of our ecosystems, helping control populations of problematic insects like beetles, including corn rootworm, and mosquitoes.

Bats of Iowa graphic

Iowa’s bats spend their summers in landscapes with trees generally near water, with some species preferring the interiors of forests and others prone to flying about city lights in search of food. Mothers raise their young in the foliage of trees, in or on buildings, around transportation infrastructure like bridges, in hollowed out trees, or in rock crevices. Any tight space close to good insect food sources near forest edges, openings, or waterways, invites bats. During winter when insect prey are no longer available, bats disappear from sight, with some species retreating deep into caves or abandoned mine shafts to hibernate, some taking shelter in attics or barns, and others leaving the state entirely to spend the winter in warmer southern climates. Many bats live alongside Iowans in every county, though they often go unnoticed because of their nocturnal lifestyle. That inconspicuous lifestyle is also the reason many Iowans don’t understand or appreciate bats or know the challenges their populations face.

Two of Iowa’s bats species are listed on the federal Endangered Species Act and are therefore the focus of special monitoring and conservation in Iowa. The Indiana Bat is an endangered species that has been on the decline throughout its Midwestern range due to habitat loss for many years, and is increasingly threatened by the exotic fungal disease called White-nose Syndrome (WNS). The northern long-eared bat was once a relatively common bat in the eastern U.S. before their population began to decline after introduction of WNS. Three additional species, little brown bats, big brown bats, and tri-colored bats, are also affected by WNS leading to increased concerned for the health of their populations in Iowa and throughout North America.

The White-nose Syndrome Threat

White nose syndrome documented White-nose syndrome (WNS) is a disease found among North American hibernating bats after they are exposed to the exotic, disease-causing fungus called Pseudogymnoascus destructans, or Pd. The Pd fungus, which scientists now know to be found throughout Eurasia, was first described in 2008 as researchers sought to understand what was causing hundreds of bats with white growth on their hairless noses and wings too die in New York starting in 2006. Since then, millions of bats in North America have died due to WNS, leading to widespread population declines in some species.

The five species of bats in Iowa that are vulnerable to WNS are those that hibernate in cool, dark places like caves and abandoned mines during winter. Other species, including the silver-haired bat and red bat have been documented to have Pd on their bodies, but do not develop the symptoms associated with WNS seen among the vulnerable species.

Species vulnerable to WNS experience variable population effects, which biologists are seeking to understand. One hypothesis is that some species are more vulnerable to WNS because their preferred hibernation locations are most suitable for growth of the fungus. Little brown bats, for example, prefer hibernation locations in the same temperature and moisture conditions conducive to Pd growth and have experienced widespread population declines. In contrast big-brown bats, which can tolerate near-freezing temperatures during hibernation, often hibernate in areas where the fungus does not flourish and have been less affected by the disease. Other hypothesis for the different levels of susceptibility among different species include differences in behavior, body size, fat stores, and the micro-biology of their wings and other hairless tissues. Among species most affected by WNS, declines in excess of 90% have been documented just a few years after the introduction of the disease to hibernating populations.

The fungus kills infected bats during the hibernation period, when their lowered body temperatures and hibernation locations create ideal conditions for the growth of this cold-loving fungus and the act of hibernation reduces the activity of their immune system that would ordinarily fight off a fungal infection. Research studies have shown that infected bats consume more of their fat reserves early in hibernation than non-infected bats, which eventually leads to increased frequency of arousals from hibernation, which then leads to even more consumption of fat reserves. In many cases, bats have been observed outside hibernacula in the dead of winter, flying in search of insect foods to restore the fat reserves they’ve lost. Of course insects are not available to consume in the dead of winter so all the additional energy used to fly for food, along with that already used to fight the infection, becomes too much for the infected bats to recover from, resulting in death during late winter.

Bats are among North America’s longest-lived mammals, generally having few young every year in favor of living long lives and producing many young over many years. Prior to WNS, few things were capable of killing large-numbers of bats, so this approach to survival and reproduction worked well to sustain their populations. However now with the new challenge of widespread mortality from WNS, those slow reproductive rates are constraining the ability of surviving bats to recover populations after large mortality events during hibernation. This is leading to widespread population declines in bats affected by WNS in North America. In New York for example, populations declined an average of 73% four years after introduction of WNS. In Indiana, a similar phenomenon was documented, with 80% declines in little brown bat hibernating populations just three years after introduction of the Pd fungus. Many smaller hibernation areas have been completely wiped out in other eastern states.

Populations of little brown bats declined 80% three years following introduction of White-nose Syndrome in an Indiana study.

White nose syndrome before and after graphic

Pd has been documented on a wide variety of substances, including equipment taken into hibernacula, surfaces within hibernacula themselves, and on bats. Therefore, preventing the spread of Pd to places bats like to go is challenging, as it seems to be easily spread by moving bats. However, wildlife biologists are actively encouraging anyone who may visit hibernacula or possible hibernation locations to follow decontamination protocols carefully. This is especially important for cavers and others who may visit areas separated by large distances or natural barriers to bat movements to prohibit introduction of the fungus into new areas in North America.

Pd Facts

Name	Pseudogymnoascus destructans, or Pd for short
Optimal growth temperatures	55-60 degrees Fahrenheit
Method of spread	Contaminated equipment or bat-to-bat
Where it grows and lives	Pd grows on a variety of surfaces including hairless regions of bats but also on surfaces in caves and mines where there are suitable temperatures.
Global distribution	Native to Eurasia with widespread distribution, spreading in North America after first documented in 2006 in New York.
Distribution in Iowa	Unknown, but probable statewide. See the map from USFWS for confirmed cases in Iowa and throughout North America.
Effects on hibernating bats	Fungal growth on hairless nose and wings leads to increased metabolic activity that disrupts hibernation and leads to starvation. Also can erode tissues, creating scars and holes in wings.

How you can help Iowa's bats

Do not disturb hibernating bats

Bats hibernate in buildings, abandoned mine shafts, and caves throughout Iowa, and especially in southern and eastern Iowa. During October to March, be sure to avoid these areas, and when it is absolutely necessary to be around them, be sure to minimize disturbances to hibernating bats to avoid waking them.

Don’t spread Pd

If you are ever in a cave or near hibernating bats, follow the decontamination protocols by the USFWS to prevent spread of Pd.

Manage forests to create bat-friendly habitats to help bats recover and raise their young.

Safely and humanely address bat conflicts

If you find bats are using your house, follow the suggestions on our problem wildlife page for safely excluding them without doing any harm.

Build a bat house to enjoy bats in your own backyard and reap the benefits of natural insect control.

Learn more

Visit the interagency White-nose Syndrome Response Team page for up to date information on the disease, recommendations for minimizing impacts, and other resources from the USFWS and other wildlife agencies.
Get the basics on Iowa's Bats in this article from Iowa State Extension and Outreach
Read more about each of Iowa’s 9 bat species in the Mammals of Iowa Field Guide.

Sources used for this article

Ballmann, A. E., M. R. Torkelson, E. A. Bohuski, R. E. Russell, and D. S. Blehert. 2017. Dispersal hazards of Pseudogymnoascus destructans by bats and human activity at hibernacula in summer. Journal of Wildlife Diseases 53:725-735.

Frick, W. F., J. F. Pollock, A. C. Hicks, K. E. Langwig, D. S. Reynolds, G. G. Turner, C. M. Butchkoski, and T. H. Kunz. 2010. An emerging disease causes regional population collapse of a common North American bat species. Science 329:679-682.

Frick, W. F., T. L. Cheng, K. E. Langwig, J. R. Hoyt, A. F. Janicki, K. L. Parise, J. T. Foster, and A. M. Kilpatrick. 2017. Pathogen dynamics during invasion and establishment of white-nose syndrome explain mechanisms of host persistence. Ecology 98:624-631.

Hayman, D. T. S., J. R. C. Pulliam, J. C. Marshall, P. M. Cryan, and C. T. Webb. 2016. Environment, host, and fungal traits predict continental-scale white-nose syndrome in bats. Science Advances 2.

Hoyt, J. R., K. E. Langwig, K. Sun, G. Lu, K. L. Parise, T. Jiang, W. F. Frick, J. T. Foster, J. Feng, and A. M. Kilpatrick. 2016. Host persistence or extinction from emerging infectious disease: insights from white-nose syndrome in endemic and invading regions. Proceedings of the Royal Society B: Biological Sciences 283.

Pettit, J. L., and J. M. O'Keefe. 2017. Impacts of white-nose syndrome observed during long-term monitoring of a Midwestern bat community. Journal of Fish and Wildlife Management 8:69-78.

Rentz, M., V. Evelsizer, S. Shepherd, and A. Janke. 2018. Mammals of Iowa Field Guide. Iowa State University Extension and Outreach.

Verant, M. L., J. G. Boyles, W. Waldrep, Jr., G. Wibbelt, and D. S. Blehert. 2012. Temperature-dependent growth of Geomyces destructans, the fungus that causes bat White-Nose Syndrome. PLoS ONE 7:e46280.

Verant, M. L., C. U. Meteyer, J. R. Speakman, P. M. Cryan, J. M. Lorch, and D. S. Blehert. 2014. White-nose syndrome initiates a cascade of physiologic disturbances in the hibernating bat host. BMC Physiology 14:10.

Chronic Wasting Disease in Iowa

Chronic wasting disease, or CWD, is a neurological disease infecting wild white-tailed deer in Iowa and other members of the Cervidae family in North America including mule deer, elk, moose, and caribou. This page provides information on the current status of the disease in Iowa, references to learn more about the disease, and some simple recommendations everyone can follow to reduce the spread of the disease and ensure safe consumption of venison harvested in Iowa.

You can help by following these recommendations

Don’t feed deer. Concentration of deer around artificial food or mineral sources can increase risk of transmission of the disease.
In harvested deer, minimize contact with portions of the deer with the highest possible CWD concentrations (brain, lymph nodes, spinal cord, spleen) and safely dispose of all processed carcasses where other deer will not contact them such as in a landfill or deep in the ground.
Cooperate with the Iowa DNR on routine CWD surveillance sampling of harvested deer if asked.
If you are hunting in or near an area with known CWD cases in wild deer (see current map below), consider following CDC recommendations and having the deer tested prior to consumption. Some tests are available through surveillance conducted by the Iowa DNR or you can submit your own samples through the hunter submission pathway with Iowa State University Veterinary Diagnostic Laboratory. Learn how to collect your own lymph node sample for testing with this video.
When waiting on CWD test results from deer harvested in CWD areas, conduct initial processing of the deer while results are pending and then discard meat from CWD-positive deer or complete processing of CWD-negative deer. Deer carcasses should always be disposed of at the site of harvest or in a landfill.
Follow state laws regarding transportation and importation of deer, elk, moose, and caribou after hunting in areas with CWD.
Captive facility operators should ensure wild deer have no interactions with captive herds.
Report any deer that appears to be sick to county conservation officers.

Learn more about CWD

	Download an article from Iowa State University Extension and Outreach that explains the science behind Chronic Wasting Disease and discusses how you can help reduce the impacts of the disease in Iowa.
	Learn about Chronic Wasting Disease in from Iowa State University wildlife disease ecologist Dr. Julie Blanchong in this video.
	Learn how to collect your own lymph node sample to submit to a diagnostic laboratory for CWD testing in this video.

CWD Distribution

	This map shows the current county-based distribution of CWD in wild white-tailed deer in Iowa based on surveillance sampling by the Iowa Department of Natural Resources on hunter-harvested deer throughout the state since 2002.
	This map from the U.S. Geological Survey shows the current distribution of CWD in wild and captive deer, elk, moose, and caribou in North America.
	Visit this interactive dashboard for more information from the Iowa Department of Natural Resources about testing and monitoring results for Chronic Wasting Disease in Iowa.

Disease Facts

CWD is in the class of neurological diseases called transmissible spongiform encephalopathies (TSE), that infects hoofed mammals in the Cervidae family (cervids), including white-tailed deer, mule deer, elk, moose, and caribou. CWD is similar to other more well-known TSE diseases like bovine spongiform encephalopathy (mad cow disease) of cattle, scrapie of sheep and goats, and Creutzfeldt-Jakob Disease of humans. All these diseases are caused by an abnormally shaped class of proteins called prions, which cause microscopic holes to form in the brain, giving it a spongy appearance, and ultimately degrade neurological functions and cause death. All known TSE diseases are fatal, although some, including CWD, have delays between initial infection and display of symptoms and death.

CWD generally has prolonged incubation period, ranging from 16 months to 3 years, before the infected animal shows any symptoms. Once symptoms are expressed, they are consistent with those seen in many more common ailments of deer and are thus not individually diagnostic of CWD infection. A symptomatic CWD-positive deer will simply appear sick, with common symptoms including drooling, poor balance, or emaciation. However, healthy-appearing deer could also be infected with the disease and not be symptomatic. Only laboratory tests conducted by disease specialists can confirm CWD infection. Most laboratory tests are performed with samples of tissue from the brain or lymph nodes of a dead deer.

All known cases of CWD in wild deer have resulted in death of the afflicted animal shortly after symptoms become apparent. There is mixed evidence among white-tailed deer and other species (mule deer and elk) affected by CWD that infection can increased vulnerability to harvest or predation before succumbing to death by the disease. There is also some evidence to suggest that successful reproduction is reduced in infected deer. Research on genetic aspects of the disease has revealed that although there is genetic variation in susceptibility of some animals, there are no known genes that completely prevent infection, suggesting all animals are potentially vulnerable to contracting the disease.

Research has shown no strong evidence that CWD is transmissible to humans or cattle. However, due to the long incubation period of prion diseases, human populations at increased risk of exposure to potentially CWD-infected cervids are undergoing long-term monitoring to help understand what risk, if any, CWD poses. The Centers for Disease Control recommends avoiding eating meat from CWD-positive animals and using caution when handling CWD-positive carcasses.

Routes of transmission of CWD among deer

Direct-transmission through bodily fluid exchange
- CWD can be transmitted from an infected deer to a healthy one through incidental exchange of bodily fluids, such as nasal discharge, saliva, urine, feces, or birthing matter. Likely routes of transmission include behaviors that bring deer into direct contact such as artificial feeding, interactions between bucks, or social interactions among family groups.
Indirect transmission through contaminated soil
- Because CWD prions, the disease-causing agent, can persist in the soil, areas where bodily fluids of deer, such as saliva, urine, feces, or birthing matter, accumulate could serve as sources of infection. Such locations include concentrated feeding areas, scrapes, or other areas where deer gather.