GoConqr has a new look! Let us know what you think.

Sign up free

Flashcards

Spongiform Encephalopathies - CW

Rachael Jones Animal Disease 2 English 47 cards

Cards in this deck (47)

  1. 1What are Spongiform Encephalopathies?A group of diseases characterised by progressive vacuolisation of brain cells
  2. 2What are the general resulting symptoms of Spongiform Encephalopathies?- Chronic progressive nervous symptoms
    - Progressive debilitation
    - Death
  3. 3List the many Spongiform Encephalopathies that are known.- BSE (cattle)
    - Scrapie (sheep)
    - Kuru (man)
    - Creutzfeld Jacob Syndrome (man)
    - variant Creutzfeld Jacob Syndrome (man)
    - Gertsmann-Straussler-Scheinker syndrome (man, hereditary)
    - Fatal Familial Insomnia (man)
    - Transmissible mink encephalopathy (mink)
    - Feline spongiform encephalopathy (cat)
    - Chronic wasting disease (deer)
  4. 4What is a prion protein?- Normal membrane associated protein, function unknown (PrPc)
    - Abnormal prion protein (PrPsc)
  5. 5What are features of the PrPsc?- Protein misfolding; higher proportion of β-sheet structure instead of α-helix (increased amyloid protein)
    - Causes other normal prion proteins to change into abnormal proteins as well
    - Is extremely stable, therefore accumulates in the brain cell
    - When ingested, acts as an infectious agent (always)
  6. 6What is the issue with PrPsc?Will build up over many years
  7. 7What are general characteristics of PrPc?- Non-infectious
    - Detergent soluble
    - Protease-sensitive
  8. 8What are general characteristics of PrPsc?- Infectious
    - Insoluble
    - Protease-resistant
    - Difficult to eradicate
    - Rendering doesn't inactivate
  9. 9Give 2 other theories for prions.- Viral hypothesis
    - Multi-component hypothesis
  10. 10When was Bovine Spongiform Encephalopathy (BSE) found?First seen in 1986
    Peaked in 1992 – 36680 cases
  11. 11What was BSE linked to?Feeding of ruminant animal/animal derived protein to cattle
  12. 12What was the result of BSE?- Ban of feeding ruminant animal protein and animal derived protein to cattle in 1988
    - Notifiable since 1988
  13. 13Who is BSE most likely to infect?- Both sexes
    - Mostly over 5 years f age (due to accumulation)
    - Lasts several weeks and invariably progressive and fatal
  14. 14What was the only way that cattle could have become infected?- Use of commercially produced compound feed containing meat and bone meal (ruminant derived)
  15. 15How could there have become infection of BSE in meat and bone meal?- From Scrapie infected sheep and used for animal derived protein
    - Possibly:
    i. Exposure to rare sporadic BSE
    ii. New strain of scrapie infectious to cattle
    iii. Imported bone meal from infected country
  16. 16What are the clinical signs of BSE?- Exaggerated fear response
    - Reluctance on corners, doors, milking
    - Occasional aggression
    - Kicking when milked
    - Head held low
    - High stepping gait (particularly hind legs)
    - Skin tremors
    - Loss of condition
    - Recumbency
  17. 17What does the incidence of BSE allow us to see?That it was a point of source contamination
    - Culled any with clinical sign and led to decrease
  18. 18What is the general trend with incidence of BSE in the UK?- 61% of all dairy farms affected (81% of BSE cases are dairy origin)
    - - Dairy receive more supplementary feed
    - 16% of all beef suckler herds affected
    - Within her incidence <2.7%
    - LOW incidence
  19. 19What is the relevance of BSE?Human variant CJD
    - BSE in cattle cause of varient Creutzfield Jacob Syndrome in people
    - Mainly younger people
    - Onset of signs to death is about 6 months
  20. 20When was the peak of vCJD in people?2001- lots of time after the 1992 peak of BSE (some not culled and then eaten)
  21. 21Is vCJD high or low incidence?Low
  22. 22What are the food safety aspects?- Contracting vCJD from BSE infected food there is insufficient evidence
    - No clustered until recently
    - One cluster from local butcher - enabled contamination of meat by CNS material
    - Further research into BSE-vCJD link - genetic susceptibility
  23. 23What is the likely spread of BSE?- Not horizontal
    - Vertical:
    i. not semen
    ii. BSE in calves that are offspring to clinical cases are higher. Highest if born after clinical onset in dam
    iii. No maternal effect in calves born 2 years before onset of clinical disease in dam
  24. 24How can you diagnose BSE?- Ante mortem: clinical signs
    - Post-mortem:
    - histopathology
    - Antibody-based tests for PrPsc protein (Western blot with brain, immunocytochemistry with brain, tonsil, third eyelid, ELISA with spinal cord/brainstem)
  25. 25What is the Cattle Tracing System (CTS)?1. The Cattle Identification Regulations 1998
    2. Cattle passports:
    - Each animal entering the food chain has passport
    - Records to be kept
    - Began 1996
    3. Numeric ear tagging from 17 January 2000
    4. CTS: computerised database operated by BCMS:
    - Full history about birth, movement and death of all cattle since 28 September 1998 (and 1996-98 retrospectively)
    - Cheque-book style passports
    - Now paper sheets
  26. 26How are older animals regulated?The Cattle (Identification of Older Animals) Regulations 2000:
    - Animals born before the onset of the cheque-book style passports
    - Registered on national database,
    - Movements recorded since 2000
  27. 27What are the feed controls?- Ruminant protein ban 1988
    - Mammalian protein to ruminants ban 1994
    - BSE Order 1996:
    - Prohibition of all mammalian protein (except milk, gelatin, amino acids, dried blood products) to ruminants (and fishmeal to animals other than ruminants)
    - Prohibition of mammalian meat and bone meal (MMBM) to any farmstock
    - Ban of MMBM at feed-handling premises
  28. 28What is the control over 30 months scheme (OTMS)?1. Government paid (£0.50/kg) for OTM cattle to be slaughtered:
    - Slaughter at dedicated abattoirs
    - Meat banned for human consumption
    - Carcasses incinerated or rendered and destroyed
    2. Withdrawn 2006: OTM cattle into food chain with restrictions (removal of VC)
    3. 4.25 million cattle slaughtered under OTMS
  29. 29What is the Offspring Cull Scheme?1. Feed ban since 1st August 1996
    - Maternal transmission only remaining route
    - Animals born after ban, at risk from infection by dam, slaughtered
    - All offspring of female BSE cases born within 2 years of diagnosis culled
    2. Scheme come to natural end
  30. 30What testing was/is done?- Before 2009 cattle over 30 months for human consumption tested
    - Later 48 months and 72 months
    -NOW Fallen stock over 48 months
    - Sheep/Goat surveillance
    - Cohorts of BSE cases
    - Results of testing: 0 positives
  31. 31What are other control measures?- Specified Risk Material Regulations 1997
    - Amendments thereafter
    - Commission Decision 2000/418/EC
    - Specified Risk Material Order 1997
  32. 32What is Scrapie?Fatal brain disease in sheep and goats
    - Experimentally given to other animals
    - Many countries and UK
  33. 33What is the additional concern with sheep and BSE?- Can be infected with BSE experimentally
    - Clinical signs in sheep very similar; possible that BSE in sheep occurred but masked by scrapie
    - No evidence for natural infection of sheep with BSE
  34. 34What are the clinical signs of Scrapie?- Change in temperament or behaviour before specific signs
    - Most between 2 and 5 years
    - Single cases in flocks
    - Any time of year but stress causes clinical signs to appear
    - Gradual development over weeks or months
    - Some cases rapid deterioration of condition
    - Occasionally dead with no signs
    - Repeated rubbing of flanks and hindquarters against objects
    - Scratching of flanks, nibbling or grinding teeth when rubbing or when rubbed firmly
    - Continued scratching of shoulder or ear with hind foot
    - Unusual or agitated nibbling of feet, legs, other body parts
    - Excessive wool loss or skin damage
  35. 35What are the signs of Scrapie in goats?Scratch legs against objects but often scratch vigorously with horns or feet
    (lesions on back from horns)
  36. 36What are the changes of behaviour associated with Scrapie?- Excitable
    - Drooping ears
    - Increased nervousness or fear response
    - Lagging behind
    - Aggression
    - Depression or vacant stare
  37. 37What are the changes in posture and movement associated with Scrapie?- Trembling
    - Unusual high stepping trot
    - Severe incoordination
    - Stumbling
    - Standing awkwardly
    - Weak hind legs
    - Unable to stand
    - Weight loss and death
  38. 38What is the issue with Scrapie?Lots of differentials
    - In most cases there are a number of signs but none are definite indication for scrapie
    - Should be considered in any sheep or goat that is showing nervous signs or behaviour changes
  39. 39How do you diagnose Scrapie?- No obvious alternative diagnosis:
    - Report case to AH for further investigation
    - Nearly 500 suspect cases a year reported
    - Only certain way to diagnose:
    Laboratory tests on tissues after death
    - No test available yet to identify infected live animals, might become available within next years.
    - Penalties for not reporting severe; heavy fines or imprisonment, or both. Scrapie compensation payments will not be made
  40. 40What will happen if you notify AH?A Veterinary Officer will visit farm:
    - If suspected, animal humanely euthanised by lethal injection
    - Samples of brain and other tissues submitted for definitive diagnosis, carcass incinerated
    - If clinical examination inconclusive, the animal placed under movement restriction on farm for 28 days.
  41. 41What happens if it is confirmed at Scrapie?- From 2004, European legislation:
    i. Compulsory Scrapie Flocks Scheme:
    - sheep on the holding genotyped.
    - Restrictions applied on sheep:
    a. Used for breeding on the holding,
    b. Sold off for breeding or slaughter
    c. Have to be destroyed
    ii. Based on their relative resistance or susceptibility
    Exceptional circumstances: sheep to be culled
    Goats always culled
  42. 42How can Scrapie be prevented?- Transmission pathway not fully understood; infected birth fluids, membranes and cleansings (placenta or afterbirth) probably spread during lambing; Sheep should not eat placenta.
    - Agent can persist for some years in environment; relatively resistant to most disinfectants
  43. 43Why are sheep genotyped?- Degree of resistance/ susceptibility
    - Amino acids - 136, 154, 171 of PrP gene
  44. 44What are the different categories for genotypes?1. Most resistant: ARR / ARR (WARNING ATYPICAL)
    2. Genetically resistant but need careful selection: ARR / AHQ, ARR / ARH, ARR / ARQ
    3. Genetically little resistance: AHQ / AHQ, AHQ / ARH, AHQ / ARQ, ARH / ARQ, ARQ / ARQ, ARH / ARH
    4. Genetically susceptible: ARR / VRQ
    5. Highly susceptible: AHQ / VRQ, ARH / VRQ, ARQ / VRQ, VRQ / VRQ
  45. 45What is the National Scrapie Plan (NSP)?- Longterm plan consisting of genotyping schemes aimed at increasing genetic resistance in national sheep flock
    - Breed specific sale and breeding restrictions apply for low resistant sheep
  46. 46What are the EU regulations?- Test prescribed number over 18 months (abattoir survey)
    - Throughout EU:
    More scrapie revealed than notified!
    Atypical scrapie identified – similar clinical signs; not really contagious and affects animals >5y
  47. 47What are features of Atypical scrapie?- Similar clinical signs; not really contagious and affects animals >5y
    - Atypical cases in sheep with more resistant alleles including ARR/AHQ (NOT VRQ!). Phenylalanine at position 141 increases susceptibility.
    - Results not consistent with experimental BSE
    - Cases detected because of more sensitive diagnostic methods
    - Work continues!

Information

Description
Animal Disease 2 (Notifiable diseases and zoonoses) Flashcards on Spongiform Encephalopathies - CW, created by Rachael Jones on 23/11/2017.
Created by
Rachael Jones · Nov 2017
Updated
Feb 15, 2018
Views
0
Rating

Feedback

What is it about?

What do you think of the new look?

How do you like it?