Scrapie Disease Overview

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Questions and Answers

What is the estimated cost of Bovine Spongiform Encephalopathy (BSE) to the Canadian cattle industry?

$10 billion

$7 billion (correct)

$5 billion

$3 billion

Which genotype is associated with high susceptibility to scrapie?

VRQ/VRQ (correct)

ARQ/ARQ

ARR/ARR

VRQ/ARR

How long can scrapie infectivity persist in the environment?

More than 15 years (correct)

Up to 10 years

Up to 5 years

Indefinitely

What is a key factor in the control of scrapie according to Canadian regulations?

Selective breeding for genetic resistance Signup and view all the answers

What was the first recorded case of scrapie, and where did it occur?

Great Britain in 1732 Signup and view all the answers

What type of fluids from infected ewes is known to present scrapie infectivity?

Amniotic fluid and tissue from placentas Signup and view all the answers

Which treatment is associated with atypical scrapie, specifically Nor98?

Low moly weight (10-12 kDa) treatment Signup and view all the answers

What was a notable challenge in scrapie eradication programs?

Decades of failure Signup and view all the answers

What is a key characteristic that distinguishes infectious prions from normal prion proteins?

Protease resistance Signup and view all the answers

Which of the following best describes the implications of bovine spongiform encephalopathy (BSE) on agriculture?

It leads to strict regulations and economic consequences in livestock management. Signup and view all the answers

Which method is most effective for inactivating prions in a laboratory setting?

Autoclaving at 134°C for 1 hour Signup and view all the answers

How does scrapie primarily spread among sheep populations?

By contact with infected soil or feed Signup and view all the answers

What is a notable challenge in detecting prion diseases such as Creutzfeldt-Jakob Disease?

The inability to culture the infectious agent Signup and view all the answers

What evidence supports the ongoing environmental persistence of prions?

Prions can remain infectious in the environment for years. Signup and view all the answers

For the control measures of scrapie, what is a critical aspect that must be adopted?

Culling infected animals to prevent transmission Signup and view all the answers

In Western blot analysis of prions, what is the relevance of using proteinase K?

It differentiates between normal and abnormal prion proteins. Signup and view all the answers

What is the main purpose of the Ruminant Feed Ban implemented in Canada in 2007?

To prohibit the feeding of mammalian-derived proteins to ruminants Signup and view all the answers

Which characteristic distinguishes Atypical BSE from Classical BSE?

Atypical BSE occurs in older cattle over 10 years Signup and view all the answers

What is a primary feature of Chronic Wasting Disease (CWD)?

Its environmental contamination persists for years Signup and view all the answers

What are Specified Risk Materials (SRM) as per the 2007 feed ban regulations?

Nervous tissue from animals aged 30 months or older Signup and view all the answers

Why is the detection of Chronic Wasting Disease (CWD) complicated?

There are no useful live tests and detection occurs post mortem Signup and view all the answers

What is one major risk associated with feeding infected meat and bone meal to cattle?

It can result in the transmission of prion diseases Signup and view all the answers

Which prion disease is recognized for its zoonotic potential?

Bovine Spongiform Encephalopathy Signup and view all the answers

What is a significant consequence of the environmental persistence of prions in relation to agriculture?

It contributes to long-term risks of prion transmission in wildlife Signup and view all the answers

Which species has exhibited a higher prevalence of Chronic Wasting Disease than white-tailed deer in Saskatchewan?

Mule Deer Signup and view all the answers

What is considered a likely transmission route of Chronic Wasting Disease in moose?

Through environmental contact Signup and view all the answers

What is the current status of treatment options for Chronic Wasting Disease?

There are no drugs or vaccines to manage the disease Signup and view all the answers

Among the following species, which is considered very susceptible to Chronic Wasting Disease?

Elk Signup and view all the answers

What percentage of male mule deer tested positive for Chronic Wasting Disease during the 2022/2023 monitoring in Saskatchewan?

34.5% Signup and view all the answers

What best describes the primary component of infectious prions?

Protein Signup and view all the answers

Which of the following methods effectively inactivates prions?

Autoclaving at 134°C for one hour Signup and view all the answers

What is the purpose of using proteinase K in distinguishing between normal and abnormal prions?

It effectively degrades normal prion protein. Signup and view all the answers

What is the estimated duration of the clinical phase for human prion diseases like Creutzfeldt-Jakob Disease?

Years Signup and view all the answers

Which of the following statements accurately describes prion disease detection methods?

Protein detection is a primary method for identifying abnormal prions. Signup and view all the answers

What distinguishes the protease resistance of abnormal prion proteins from that of normal prion proteins?

Abnormal proteins remain intact after protease treatment. Signup and view all the answers

Which statement best describes the antibody response to prion infections?

No useful antibody response is detected. Signup and view all the answers

What type of diseases are characterized by abnormal prion protein accumulation?

Prion diseases Signup and view all the answers

What is the primary source of infectious prions in infected animals?

Lymphatic tissues Signup and view all the answers

How does the incubation period of prion diseases in humans generally compare to that of infected cattle?

Humans have a longer incubation period than cattle Signup and view all the answers

Which of the following statements correctly describes the characteristics of the infectious form of prion protein?

It contains the same amino acids as normal PrP Signup and view all the answers

What role does the Prion Protein (PrP) play in the host organism?

Expression on the cell surface Signup and view all the answers

Which prion disease is characterized by a long incubation period and affects various animal species?

Chronic Wasting Disease Signup and view all the answers

Which statement regarding the infectivity of prions in animal brains is true?

Mink brains can contain 1-10 million infectious units Signup and view all the answers

What are the characteristics of prion diseases in terms of treatability and resistance to inactivation?

They are fatal with no cures and show extreme resistance to inactivation Signup and view all the answers

Which prion disease affects humans and is associated with consumption of infected beef?

Variant CJD Signup and view all the answers

What are the characteristics of the PRNP gene related to scrapie resistance and susceptibility?

ARR/ARR genotype indicates high resistance to scrapie. Signup and view all the answers

Which of the following statements best describes the transmission of scrapie among sheep?

The placenta of infected ewes is a significant source of infectivity. Signup and view all the answers

What is the primary challenge faced in the eradication of scrapie over the decades?

Environmental persistence of scrapie infectivity. Signup and view all the answers

Which treatment is associated with the study of atypical scrapie and involves proteinase K?

Protein characterization and detection through increased sensitivity. Signup and view all the answers

What is the estimated economic impact of Bovine Spongiform Encephalopathy (BSE) on the Canadian cattle industry?

Estimated to be around $7 billion. Signup and view all the answers

What is a unique feature of Atypical Scrapie compared to Classical Scrapie?

It presents increased proteinase K sensitivity. Signup and view all the answers

Which aspect is crucial for producers to minimize the risk of scrapie in their sheep flocks?

Implementing selective breeding for genetic resistance. Signup and view all the answers

What is a significant characteristic of the environmental contamination associated with scrapie?

Contamination can persist for more than 15 years in the environment. Signup and view all the answers

Which age group of cattle is primarily affected by Atypical BSE?

Cattle aged 10 years and older Signup and view all the answers

What is a critical environmental characteristic of Chronic Wasting Disease (CWD)?

It can persist in the environment for years Signup and view all the answers

What distinguishes Atypical BSE from Classical BSE?

The origin of the prion protein characteristics Signup and view all the answers

Which of the following statements about the Ruminant Feed Ban is accurate?

It prohibits the feeding of poultry litter to ruminants Signup and view all the answers

What is the major zoonotic risk associated with Bovine Spongiform Encephalopathy (BSE)?

It poses a threat through consumption of infected meat Signup and view all the answers

Which category of materials is designated as Specified Risk Materials (SRM)?

Nervous tissue from animals over 30 months of age Signup and view all the answers

What is a notable feature of Chronic Wasting Disease regarding testing methods?

Post-mortem examinations provide useful testing results Signup and view all the answers

What is the primary cause of Classical BSE in cattle?

Feeding contaminated meat and bone meal Signup and view all the answers

Study Notes

Scrapie

A disease of sheep and goats
First recorded case in the UK: 1732
First case in Canada: 1938
First case in the U.S.: 1947
Worldwide distribution
Scrapie eradication has been challenging over decades, but current approaches are successful

Scrapie Transmission

Contagious
Scrapie infectivity is present in fluid and tissue from the placentas of infected ewes
Environmentally persistent: >15 years

PRNP Gene

+H -COO- 3N-
```
                   136     154   171
```
ARR resistance to scrapie

VRQ susceptible to scrapie

VRQ/VRQ highly susceptible ARR/ARR highly resistant

Controlling Scrapie: Canadian Food Inspection Agency (CFIA) Program

Scrapie is a Reportable Disease
- Suspect cases must be reported to a CFIA veterinarian immediately
Sheep documented with scrapie and all animals exposed to the same birthing environment must be destroyed
- Producers are compensated for the loss of their animals
Producers can consider selective breeding for genetic resistance to scrapie to minimize the risk of scrapie in their sheep flock

Atypical vs Classical Scrapie

Atypical Scrapie
- Nor98
- PK treatment: low molecular weight (10-12 kDa)
- Increased PK sensitivity
- More abundant in the cerebellum and cortex than the brainstem
- Identified in "scrapie-resistant" sheep, A136 R154 R171
- Abundance?
Classical Scrapie
Bovine Spongiform Encephalopathy
- Friesian cow, 9 years old
- ~200,000 cattle (Great Britain)
- 26 Cattle (North America)

The Cost of BSE

The cost of BSE to the Canadian cattle industry has been estimated to be around $7 billion dollars.

Prion Infectivity and Food Chain

Prions are resistant to inactivation
Prion infectivity remains in meat and bone meal
Infected meat and bone meal was added to cattle feed

Ruminant Feed Ban

Prohibits the feeding of:
- Most mammalian-derived proteins to ruminants
- Poultry litter and restaurant waste to ruminants
Canada: 1997.
Feed ban 2007 (July 12, 2007)
- SRMs are also banned from all animal feeds, pet foods, and fertilizers.
- SRMs = "Specified Risk Materials": nervous tissue (skull, brain, spinal cord) from animals 30 months or older

BSE in North America

26 known BSE cases
- 1 imported from Great Britain (Red Deer, 1993)
- 5 US
- 20 or 21 Canada (Wash 2003)
A = Atypical BSE

Classical vs Atypical BSE

Classical BSE
- Caused by feeding cattle contaminated feed
- Average age of infected cattle: 4-5 years

Atypical BSE

Very old cattle
- 10 years +
Appears to be sporadic (randomly occurs)
Distinguished from classical BSE by the characteristics of the abnormal prion protein
NOT linked to animal feed (Meat and bone meal)!

Chronic Wasting Disease

Contagious Prion disease
Affects the central nervous system and lymphatic system.
Always fatal
No treatment or cure
Complicated detection
- Post mortem --- No useful live tests
CWD Strains

Chronic Wasting Disease Environmental Contamination

Persists in the environment for years
Long Preclinical Phase
Slow Spread
Confined to Cervids
Zoonotic?

Zoonotic Potential

Prion Disease Zoonotic?
Scrapie No
Bovine Spongiform Encephalopathy Yes
Chronic Wasting Disease ?

PrPC

Sequence as PrPC
- Metal homeostasis
- Resistant to degradation
Necessary for prion infection

PrPC Prion Replication

PrPSc - Converting PrPC to PrPSc
PrPC - Normal Form of prion protein
PrPSC - Abnormal form of prion protein

Detecting Prion Diseases: Factors

Infectious agent
- Abnormal protein (PrPSC)
- No virus to culture or detect
- No bacteria to characterize
Antibody Response
- None useful
- Serology not appropriate
Extended Preclinical Stage, Short Clinical Stage
- Years
  - Deer (chronic wasting disease)
  - Cattle (bovine spongiform encephalopathy)
  - Sheep (scrapie)
- Decades
  - Humans (Creutzfeldt Jakob Disease)

Protease Resistance

Means of distinguishing normal from abnormal prions
Uninfected
- Normal form of prion protein (PrPC)
  - PrPC + proteinase K = No protein
Infected
- Normal Form of prion protein + PrPCWD
  - PrPCWD + PrPC + proteinase K = PrPCWD

Protease Resistance: Uninfected vs Infected

Uninfected Infected
PrPC PrPC PrPSC

     Proteinase K                                Proteinase K

                                         PrPSC

Western Blot Analysis: Distinguishing PrPC from PrP CWD

CWD+ CWD-

                                             32 kDa

```
  PK   - + -   + - +           - +
```

               50 ug/ml proteinase K (PK) 30 minutes

```
  PrP Antibody: 6H4 
```

Obex Staining (CWD)

No detectable Obex score 1
```
          Obex score 4
```

Infectious Prions Resist

Chemical inactivation
- Acids
- Base
- Detergent
- Extreme conditions (1 N NaOH) will inactivate
Standard Sterilization Methods
- Autoclaving---medical sterilization (120 o C 20 min)
- Extreme conditions (autoclaving at 134 C for 1 hour) will inactivate
UV and gamma irradiation levels that inactivate most bacteria and viruses

Healthy or Infected?

Protozoa, Helminths, Fungi Bacteria Viruses Prion Disease

 Eukaryotic                 Prokaryotic          DNA or RNA       Protein
                                                      +
                                                Protein coat

                        Nucleic Acid Detection                  Protein Detection

Prion Diseases

Prion diseases are fatal neurodegenerative diseases caused by misfolded proteins called prions.
These prions are highly resistant to inactivation and can persist in the environment for extended periods.

### Prion Diseases & Their Hosts

Scrapie: Primarily affects sheep and goats.
Bovine Spongiform Encephalopathy (BSE): Affects cattle.
Chronic Wasting Disease (CWD): Impacts cervids, including deer, elk, and moose.
Creutzfeldt-Jakob Disease (CJD): Occurs in humans.
Variant CJD (vCJD): A human prion disease linked to BSE.
Kuru: A human prion disease transmitted through ritualistic cannibalism.

Characteristics of Prion Diseases

Spongiform Degeneration: The brain tissue develops holes, giving it a sponge-like appearance.
Transmissible: Prion diseases are spread through the transfer of infectious prions.
Long Incubation Period: It can take years to decades for symptoms to manifest after exposure.
Extended Preclinical Stage: The disease can exist without visible symptoms for an extended period.
Fatal: There is currently no cure for prion diseases.
Extreme Resistance to Inactivation: Prions are highly resistant to conventional sterilization methods.

The Prion Protein (PrP)

Normal Form (PrPC): Expressed on the cell surface of neurons, glia, and other peripheral cells.
Infectious Form (PrPSc): Misfolded version of PrPC with a different conformation.
PrPSc Conversion: PrPSc acts as a template to convert PrPC into the infectious form, leading to prion replication.

Detecting Prion Diseases

Difficult to Detect: Currently, no reliable live tests exist.
No Antibody Response: Serology is not effective for detecting prion infection.
Protease Resistance: PrPSc resists proteinase K digestion, a characteristic used to distinguish it from PrPC.

Environmental Persistence

Prions are highly resistant to inactivation and can persist in the environment for extended periods.
This poses challenges for managing prion diseases, particularly regarding contaminated surgical instruments, animal products, and environmental contamination.

Scrapie

History: First recorded in the UK in 1732, with global distribution.
Transmission: Contagious through direct contact and environmental contamination.
Eradication Efforts: Extensive but challenging due to prion resilience.
Genetic Resistance: Sheep with certain PRNP gene variations (ARR) have increased resistance to scrapie.
Atypical Scrapie: A strain distinct from classical scrapie, showing increased PK sensitivity and distribution in the brain.

Bovine Spongiform Encephalopathy (BSE)

Origin: Linked to the feeding of meat and bone meal contaminated with prions.
Impact: Caused significant economic losses and led to widespread bans on feeding mammalian-derived proteins to ruminants.
North American Cases: Approximately 26 cases documented, with 1 imported from the UK and the rest attributed to sporadic events.
Atypical BSE: Distinguished from classical BSE by age of infected cattle, characteristics of the abnormal prion protein, and is not believed to be linked to animal feed.

Chronic Wasting Disease (CWD)

Impact: Affects cervids and is a significant concern for wildlife populations.
Transmission: Contagious through direct contact, environmental contamination, and possibly through ingestion of contaminated feed.
Zoonotic Potential: Research ongoing to determine if it poses a threat to humans.
Current Status: Spreads throughout the US and Canada, with a substantial increase in prevalence.
Control Challenges: No drugs, vaccines, or cures available; depopulation and population reduction efforts are ongoing.

CWD Susceptible Species

White-tailed Deer: Highly susceptible and contribute to disease spread.
Mule Deer: Highly susceptible with increased prevalence in Alberta and Saskatchewan.
Elk: Susceptible with both free-ranging and captive populations affected.
Moose: Susceptible but less common than other cervids, but environmental transmission is possible.
Caribou: No cases reported in North America, but considered susceptible.

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Description

This quiz covers the disease scrapie, which affects sheep and goats. It includes information about its history, transmission methods, the PRNP gene's role in susceptibility, and how it is controlled under the Canadian Food Inspection Agency regulations. Test your knowledge on this contagious and challenging livestock disease.