Prion Diseases = Transmissible Spongiform Encephalopathies (TSE)

Prion – Protinacious and infectious• a mis-folded protein• autocatalytic• self-propagating

• genetic, sporadic, transmitted• all prion diseases affect neural tissue• all are incurable and fatal• all mammals are susceptible

– Creutzfeldt-Jakob (CJD)– Scrapie

• Transmissible mink encephalopathy (TME)

• Kuru• Bovine spongiform encephalopathy

(BSE)– new variant (nv) CJD

– Chronic wasting disease (CWD) ?

• all associated with an abnormal protein conformer in the brain and subsequent neurodegeneration.

• PrPC – endogenous conformer found in a variety of tissue

• PrPSc- aka PrPRes - the misfolded conformer neurodegenerative disease.– PrP – protease resistant protein– C – cellular; Sc – scrapie; Res – proteinase resistant

• PrPC – found on cell membranes– binds copper– a copper-dependent anti-oxidant?– may have function in maintenance of long-

term memory

nerve and immune cell

• PrPc

– -helix-rich– susceptible to

proteases

• PrPSc

– -pleated sheet-rich – not susceptible to

proteases

• aa sequence is identical

plaques of aggregated PrPSc and vacuolization in brain

TSE

Transmission – oral – Ex. sheep cow

Animals slaughtered

Inedible materials go to rendering

Low temperature fat removal

Solvent extraction

Fat Steam strip solvent

Dried = Meat and Bone Meal (MBM)

Used for feed

Chronic Wasting Disease

Pathogenesis• Likely route in infected animal

– Oral GI tonsil & GALT enteric nerves obex of medulla oblongata widespread distribution lymphoid tissue and CNS

Thalamus of white tail deer with CWD

Amyloid plaques in paraffin-embedded tissue Congo red-stained amyloid plaques

tonsil

Scrapie• Great Britain and western Europe

more than 250 years ago • 1947 – scrapie found in domestic

sheep in US (Michigan)• Primarily Suffolk breed • USDA APHIS survey (2002-2003)

– 1 positive out of 500 cull sheep positive

• Probable transmission ewe to offspring and to other lambs through contact with the placenta and placental fluids

• Signs usually appear 2 to 5 years after infection

• Sheep may live 1 to 6 months or longer after the onset of clinical signs, but death is inevitable

• Only Australia and New Zealand recognized scrapie-free

Scrapie

• Irritation:– repeated rubbing of flanks and

hindquarters against objects– repeated scratching of the

flanks – nibbling or grinding teeth when

rubbing– continued scratching of the

shoulder or ear with a hind foot – unusual nibbling of the feet, legs

or other parts of the body – excessive wool loss or skin

damage

Scrapie

• Changes in behaviour (from normal):– excitable & increased

nervousness– drooping ears – lagging behind – aggression – depression or vacant stare

Scrapie

• Changes in posture and movement:– trembling – unusual high stepping trot,

hopping like a rabbit or swaying back end

– loss of coordination – stumbling – standing awkwardly – weak hind legs – unable to stand

• Later signs: – weight loss – death http://www.youtube.com/watch?v=S4bhexPs1FA

Management of Scrapie• USDA coordinates National

Scrapie Eradication Program (NSEP) – participation by state

governments and industry, specifically individual producers

• Producers identify and keep detailed records on goats/sheep

• Annual inspections by certified vet

• Report suspect animals• Use genetic selection

Management of Scrapie• Scrapie Flock Certification

Program – Producer enrolls his/her flock. – Marketing advantage

• Identify all animals over1 year of age • Maintain records• Flock/herd inspected annually • Report scrapie-suspect animals to

proper animal health authorities • Submit tissue samples of any scrapie-

suspect animals and from animals suspected of having other neurological or chronic, debilitating diseases

• Report acquisitions of animals from flocks with a lower status or from flocks not participating in the program

• Certified Scrapie-free after 5 years of closed flock

CWD

CWD• Captive and wild cervids

– white-tailed deer– mule deer– elk– moose

• First observed, 1967, Colorado Division of Wildlife’s Research Facility in Fort Collins, CO (initially thought to be malnutrition)

• 1977 CWD determined to be TSE (mule deer)

• 1981, 1st wild animal (elk) from Rocky Mt. Nat’l Park, diagnosed

• Models suggests may have been present in free-ranging populations of mule deer for more than 40 years

CWD

• Susceptibility of other cervids to CWD not known

• Cattle and other domestic livestock appear to be resistant to natural infection (research continues)

• Privately owned cervid facilities (POC) may allow spread

Origin of CWD

• Possible link to scrapie (derived from)?• Deer contact with scrapie agent either on shared

pastures or in captivity somewhere along the front range of the Rocky Mountains (location of high levels of sheep grazing occurred in the early 1900s.) – sheep pasture at NWRC

• In vitro models suggest less species barrier to interspecies TSE transmission between deer, elk, and sheep than between these cervids and either cattle or humans

• Or CWD is independent origin specific to deer ?

Wildlife Fences• CWD

transmission control by limiting contact between infected and non-infected animals

• > 3 m woven wire

• $10 to $20 per m• Cost:benefit ratio

Transmission Ecology - CWD

• Elk Wallows as potential sites of transmission?– 1-2 times per

season– Low probability– Mineral licks might

be more important (multi-spp.)

USDA APHIS WS• National Wildlife

Research Center (NWRC)

• Congressional appropriations for research and management of CWD (and many other conflict issues) Dr. Kurt VerCauteren

NWRC - CWD• Evaluation and Management of Chronic Wasting

Disease TransmissionPROJECT GOAL: Study ecology of CWD, assess the potential for CWD transmission at the interface between wild and domestic cervids, and develop methods that reduce or eliminate CWD transmission and spread.– Objective 1: Determine extent of interactions between domestic and

wild cervids and develop cost-effective means of reducing interactions.

– Objective 2: Explore a CWD vaccine.– Objective 3: Develop methods to detect CWD prions and

decontaminate infected sites.– Objective 4: Assess the role of predators and scavengers in CWD

epidemiology.– Objective 5: Develop improved cervid census and removal

techniques.– Objective 6: Evaluate white-tailed deer and mule deer ecology

along riparian areas relative to the transmission and spread of CWD.

NWRC - CWD• CWD Vaccine

– Experimental vaccine trial in the widely used RML mouse scrapie model system yielded two promising candidates for further study. 

– Currently, the two CWD vaccine candidates have been resynthesized, formulated, and used to vaccinate mule deer, making this the first known application of a CWD vaccine in the target species

– Currently, prime and booster injections of the vaccine have been administered to mule deer housed at CSU’s Animal Population Health Institute paddocks, a CWD-free environment. 

– Preliminary results show that the mule deer are producing good antibody titers to prion protein.

– Deer passed more than 120 days since their disease challenge– Conclusive results on how well the CWD vaccine works in mule deer will

not be known for another year to 18 months.  – Additional vaccine work on an oral CWD vaccine.

• Testing of Hydrolysis and Rendering Effects on Prion Infectivity– How effective hydrolysis and rendering procedures are at

destroying infectious prion material to determine if these methods are viable carcass waste-disposal options

– Hydrolysis process using lye under increased pressure and temperature to degrade biological material 

– Rendering process of cooking material in oil  – Using mouse model (injecting material into brain)– Six months after inoculation, some of the mice are showing

signs of developing the disease.  – Preliminary results showed 0 of the 23 mice injected with

hydrolyzed material died – 16 out of 23 mice injected with rendered material died within

about 244 days of injection

• Validation of a Live Test for CWD– 2006, a practical live test (rectal biopsy) for

CWD in elk developed– Being tested in pen studies

CWD in WI

• Discovered wild deer in 2001/2002

• >700,000 deer hunters

• Avg 460,000 deer harvested

• Generates >$500 million retail

• ~$1 billion impact to state’s economy

CWD in WI

• Discovered wild deer in 2001/2002

• Spent $40+ million testing and drastically reducing deer populations since

• Initially planned to kill all estimated 30,000 deer in focal area

• Saskatchewan spent $30+ million

CWD in WI

CWD in WI

CWD in WI

CWD in WI

CWD in WI

CWD in WI

• Surveillance program to detect 1% prevalence

• Difference in age/gender – 0.16% fawns +– Increase prevalence

with age (faster in males)

– 2-3% yearlings +– 2+ yrs (M = 10%, F =

4-5% +)

CWD in Michigan

• February 28th, 2003

Governor Granholm signed an executive order creating a task force to address the threat of CWD in Michigan's deer and elk populations

Includes 5 voting members appointed by the Governor

Directors of the MDA, Community Health, DEQ, DNR, State Police, and Transportation = non-voting members of the task force

CWD in Michian

• April 15, 2004– Granholm Signs Executive Order Transferring

Regulation of Privately Owned Deer, Elk Facilities to DNR (from MDA)

CWD in Michigan• Michigan : Michigan's First Case of Chronic Wasting Disease

Detected at Kent County Deer Breeding Facility

Date: August 25, 2008 Source: Michigan Department of Natural Resources

LANSING - The Michigan departments of Agriculture (MDA) and Natural Resources (DNR) today confirmed the state's first case of Chronic Wasting Disease (CWD) in a three-year old white-tailed deer from a privately owned cervid (POC) facility in Kent County.

The state has quarantined all POC facilities, prohibiting the movement of all - dead or alive - privately-owned deer, elk or moose. Officials do not yet know how the deer may have contracted the disease. To date, there is no evidence that CWD presents a risk to humans.

CWD in Michigan

• Michigan : Tests of More Than 1,000 Deer Find No More Cases of Chronic Wasting Disease

Date: October 07, 2008Source: The Grand Rapids Press

Statewide, 1,095 deer have been tested, with 964 testing clean and 131 awaiting results. More than 300 wild Kent County deer have been tested and found to be clear of chronic wasting disease after the highly contagious disorder was found in one northern Kent County farm-raised deer in August.

Approximately $1 million spent on testing

CWD and Hunting

• No evidence of infection of humans• Precautions:

– Latex or rubber gloves when dressing/handling– Bone out meat, avoid cutting bone, spinal cord, into

brain– General hygiene– Avoid consumption brain, spinal cord, eyes, spleen,

tonsils, lymph nodes– Avoid consuming positive animal