Wildlife Diseases of Concern for Minnesota’s Deer Populations Michelle Carstensen, Ph.D Wildlife Health Program Supervisor MN DNR, Division of Wildlife

Why do wildlife get diseases? Exposure to a wide variety of pathogens Viruses Bacteria Parasites Interactions with domestic livestock Social behavior Artificial baiting and feeding Nutritional stress and winter severity

What is Chronic Wasting Disease? CWD is a slowly progressive, brain disease of deer, elk, and moose CWD belongs to the family of diseases known as transmissible spongiform encephalopathies (TSE) or prion diseases Other TSEs include scrapie (sheep), BSE (cattle), Jakob- Creutzfeldt (humans) Photo by Terry Kreeger

What Does the Name Mean? Transmissible – Can be spread from animal to animal Spongiform – sponge-like (full of holes) Encephalopathy – brain disease Photo: Chronic Wasting Disease, courtesy of CO State University College of Veterinary Medicine & Biomedical Sciences

Understanding the TSE Agent Not caused by a virus, fungus, or bacteria Disease is transmitted by a misshapen host protein, called a prion

Characteristics of all TSEs, including CWD Neurologic clinical signs: dementia, incoordination, excessive salivation, abnormal behavior, etc. No treatment, always fatal No host immune response, thus no easy vaccine or diagnostics for live animals Difficult to inactivate infectivity Unconventional infectious agent Spread animal-to-animal; persists in the environment

What we know about CWD Spread animal-to-animal (saliva, feces, urine) Early detection looks for prion accumulation in the retropharyngial lymph nodes and obex portion of brain Average 16 months or more (up to 3 yrs) from exposure to clinical disease Prions remain infectious in environment (soil) for years Only known in cervids; no evidence of transmission to other wild mammals or humans Photo by Terry Kreeger

CWD Surveillance in Minnesota Risk-Based Surveillance 2005 To Present Based On— Suspect- deer exhibiting CWD symptoms New infection found in adjacent state- done several times for WI infections Association with positive captive cervid farm- Conduct surveillance around areas known to have CWD (n=5) 5 CWD-positive cervid farms in MN

An Outbreak of Bovine Tuberculosis in Minnesota’s Wild Deer in NW MN

The Disease….. Bovine tuberculosis (TB) is an infectious disease that is caused by the bacterium Mycobacterium bovis (M. bovis). Bovine TB primarily affects cattle, however, other animals may become infected. Detected in beef cattle in NW MN in 2005, total of 12 herds were infected MN lost it’s federal TB-Free status in 2006 Significance? Trade & economic losses are severe where infection is discovered

Close-up of infected lungs Pus-filled nodules on lungs of a deer infected with bovine TB

Thief Lake WMA

How is MNDNR Managing Bovine TB in Deer? Reduce deer densities Special hunts, sharpshooting, landowner shooting permits, aerial gunning Restrict recreational feeding of deer Ban recreational feeding Address risk mitigation at the cattle-deer interface Deer-proof fencing program Change farming practices to reduce risk

Other Diseases Occurring in Deer

Epizootic Hemorrhagic Disease An acute, infectious, often fatal viral disease of some wild ruminants. Characterized by extensive hemorrhages, has been responsible for significant die-off of deer in other states Transmitted by a biting fly or gnat Death is sudden

Epizootic Hemorrhagic Disease South Dakota estimated that over 3000 deer died of EHD in 2012 Disease showed up in August as deer sought water and shade as the fever and other symptoms showed up. Can also infect other animals but effect is not as severe It is not considered a threat to humans

Parasites of Deer the Hunter may Encounter Liver Flukes Ticks & Mites Bot Fly Larvae

Liver flukes are a large trematode (flatworm

Liver flukes normal definitive host is the white-tailed deer. Moose, cattle, mule deer, sheep, and cattle can also be infected and are dead end- hosts for flukes Dead-end hosts mean they can’t complete their life cycle in these hosts An aquatic snail is required to complete the life cycle Generally do not cause illness in deer but can cause harmful secondary infections

The female fly while in flight ejects minute larvae into the nostrils of the host deer. Larvae become attached in clusters and develop at the base of the deer’s tongue Are expelled by deer when larvae are fully developed Signs in deer may be snorting

Skin Diseases Mange (mites) Dermatophilosis (bacterial) Other hair loss

Cutaneous Fibromas Warts caused by a virus

Seromas Fluid-filled cyst, typically associated with pucture-type injuries

What Preventive Measures Should Hunters Take? Do not shoot, handle or consume a deer that is acting abnormally or appears to be sick. When field-dressing game, wear rubber gloves and minimize the use of a bone saw to cut through the brain or spinal cord (backbone). Bone out the meat. Minimize contact with and do not consume brain or spinal cord tissues, eyes, spleen, or lymph nodes. Always wash hands thoroughly after dressing and processing game meat. Cook meat to 165 degrees F.