BSEvCJD: The European Ongoing Story - PowerPoint PPT Presentation

Title: BSEvCJD: The European Ongoing Story


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BSE/vCJD The European On-going Story

• Prof J Ralph Blanchfield, MBE
• Chair, External Affairs and Past President
• Institute of Food Science Technology
• President Elect 2003-2006
• International Academy of Food Science
  Technology
• IUFoST Governing Council Member
• Food science, food technology and food law
  consultant
• E-mail jralphb_at_easynet.co.uk Web
  www.jralphb.co.uk

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BSE/vCJD The European On-going Story

• ? Containment of risks of ?
• a fatal cattle disease and
• a fatal human disease
• caused by entities which appear not to obey the
  rules of microbiology or toxicology
• with incubation periods 3-5 years in cattle,
  6-30 years or more in humans
• with clinical signs developing only very late in
  the incubation period and
• no ante mortem test

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Institute of Food Science Technology

• the UK-based professional qualifying body of food
  scientists and technologists
• democratic, not-for-profit, self-governing,
  self-funding
• totally independent of government, of industry,
  and of any lobbying groups or special interest
  groups

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Institute of Food Science Technology

• professional members elected on academic
  qualifications and relevant experience, and
  signed undertaking to comply with the Institute's
  ethical Code of Professional Conduct

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Institute of Food Science Technology

• The first of its four purposes is
• to serve the public interest by furthering the
  application of science and technology to all
  aspects of the supply of safe, wholesome,
  nutritious and attractive food, nationally and
  internationally.

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Institute of Food Science TechnologyWhy
concerned with BSE?

• New disease affecting major food source -
• Rapid UK escalation to epidemic proportion
• Not veterinarians, not neurologists, not
  pathologists, not geneticists, not molecular
  biologists, not epidemiologists, not BSE
  researchers
• Experts study small parts of picture close-up
• Role of food scientists -
• to stand back and observe whole picture.

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BSE

• Jigsaw many missing pieces
• Every successive update of the IFST Information
  Statement on BSE has emphazised
•  
• "While that sums up the present state of
  knowledge, scientists always have to keep open
  minds. They have to act on existing knowledge
  while recognizing that further research will
  bring new information and knowledge, which may in
  turn lead to revised conclusions. We welcome the
  devotion of substantial extra resources to
  research in this field."

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BSE

• Origin?

Scrapie in rendered meat and bone meal (MBM) feed
becoming changed when passaged through
cows? Or Originating from a one-in-a-million case
of sporadic BSE infection in a cow which was
rendered and recycled? Probably never be able
to prove which. Role of contributory factors?
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BSE

• Either way -

• Rendered MBM was the vehicle.
• Role of John Wilesmith
• Wilesmith J W et al (1988) "Bovine spongiform
  encephalopathy epidemiological studies on the
  origin", Veterinary Record , 123, 638.
• Wilesmith J W et al (1991) " Bovine spongiform
  encephalopathy epidemiological studies on the
  origin", Veterinary Record , 128, 200-203.

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BSE

• Rendered MBM was also the vector
• Key factor in subsequent development of the
  epidemic was the use of MBM as cattle feed, as
  demonstrated when its prohibition led to
  successive year-by-year reductions in confirmed
  new cases.

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BSE
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BSE
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BSE
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BSE
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BSE

• Incidence Rest of World
• 2000 452 cases
• 2001 987 cases (Detwiler Effect?)
• 2002 864 cases
• 2003 643 cases
• 2004 524
• 2005 36 (to 14 March 2005)
• Improved surveillance efforts
• Passive versus active surveillance
• 2001 increase due to active testing

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BSE

• Incidence Great Britain
• Passive surveillance
• 1988 to date 179,124 cases
• 2000 1,311 cases
• 2001 781 cases
• 2002 445 cases
• 2003 173 cases
• 2004 82 cases
• 2005 5 cases (at 4 March 2005)
• Active surveillance 1,613
• (1 January 1999 to 4 March 2005)

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BSE

• Infective agent Prion (Pree-on)
• Misfolded protein molecule that causes normally
  folded prion protein molecules to misfold.
• Separate lines of research provide strong
  evidence for the prion hypothesis.

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BSE

• Infective agent Prion (Pree-on)
• Concept J S Griffith (1967)
• Formalized S B Prusiner (1982)
• Does not obey conventional rules of microbiology
  or of toxicology
• Replicates with no DNA or RNA
• Misfolded prion protein molecule that causes
  normally folded prion protein molecules to
  misfold
• ?-helix ? ?sheet structure (PrPsc)
• Largely protease-resistant (PrPres)
• Resistant to heat, irradiation, most practicable
  chemical treatments

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BSE

• Infective agent Prion (Pree-on)
• Collinges group (2004) have characterised two
  distinct prion strains derived from BSE
• transmissions to inbred mice. These data indicate
  a crucial involvement of the host
• genome in modulating prion strain selection and
  propagation in mice. It is possible that
• multiple disease phenotypes may also be possible
  in BSE prion infection in humans and other
  animals.
• Lloyd SE et al, (2004), J Gen Virol, 85,
  2471-2478.

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BSE

• Infective agent Prion (cont)
• Four alternative treatments have been proposed
  for decontaminating prion infectivity on
  surfaces, including a phenolic disinfectant, an
  alkaline cleaner, the combination of an enzymatic
  cleaner and vaporised hydrogen peroxide (VHP) and
  a mixture of two proteolytic enzmes and a
  detergent.
• .
• The first two appear to be proprietary
  disinfectants already marketed by STERIS.

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BSE

• Infective agent Prion (cont)
• Langeveld J et al (2003) Journal of Infectious
  Diseases, 1 December 2003 have shown that, when
  brain tissues from cows with BSE and sheep with
  scrapie are treated with a bacterial enzyme
  keratinase, the enzyme fully degraded the prion,
  rendering it undetectable.

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BSE
Source SCI Biotechnology Group
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BSE

• PrPsc model structure based on electron
  crystallography
• Source Wille et al (2002), PNAS, 99, 10, 1073

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BSE

• Infectivity of bovine materials?
• Brain, spinal cord,
• Retina (?)
• Dorsal root and the trigeminal ganglia
• Bone marrow slightly infectious
• Distal ilium of calves (experimentally induced)
• Muscle? Milk? Blood? Not detectable by current
  methods.
• BUT

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BSE

• Infectivity of bovine materials?
• In January 2005 Aguzzis group has shown in mice
  suffering from any of five inflammatory diseases
  of kidney, pancreas or liver. that infective
  prions may spread further in the body to those
  tissues. In all cases,
• chronic lymphocytic inflammation enabled prion
  accumulation in otherwise prion-free organs.
• Heikenwalder et al., Chronic Lymphocytic
  Inflammation Specifies the Organ Tropism of
  Prions, Science 2005 0 11064601

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BSE

• Infectivity of bovine materials?
• No infectivity yet detected in blood of BSE
  infected cattle
• but
• BSE transmitted to one of six scrapie-free sheep
  by blood transfusion from apparently still
  healthy scrapie-free sheep fed orally with brain
  of BSE infected cattle.
• Houston F et al (2000) Transmission of SE by
  blood transfusion in sheep, Lancet, 356,
  999-1000.
• Hunter, N et al (2002), Journal of General
  Virology 83, 2897-905.

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BSE

• Infectivity of bovine materials?
• Further work resulted in a second transmission of
  BSE and four new cases of transmission of natural
  scrapie. Positive transmissions occurred with
  blood taken at pre-clinical and clinical stages
  of infection. These results confirmed the risks
  of TSE infection via blood products and suggest
  that the measures taken to restrict the use of
  blood in the UK have been fully justified.
• Hunter, N et al (2002), Journal of General
  Virology 83, 2897-905.

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BSE

• The early UK containment controls (1988)
• to slaughter and destroy animals clinically
  diagnosed on the farm or elsewhere
• to prohibit the feeding of material containing
  animal protein derived from ruminants to cattle
  and other ruminants  
• to prohibit Specified Bovine Offals (SBOs) from
  the food or feed chain
•  

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BSE
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BSE

• UK health controls since 1996 ?
• Enhanced and strictly enforced ban on mammalian
  MBM for all farm animals, with recall of all
  existing stocks of MBM.
• Exclusion of SRMs from the food or feed chain
  (SRM from 1995 includes vertebral column and
  dorsal root ganglia).
• Over Thirty Months Scheme (OTMS) in which cattle
  aged over thirty months are slaughtered in
  designated abattoirs when they came to market and
  incinerated or rendered.
• Offspring cull, of offspring born after 1 August
  1996 to dams in which BSE was confirmed.
• Compulsory Cattle Passport traceability system.

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BSE

• UK health controls since 1996 (cont)
• On 2 December 2004 , following advice from SEAC
  and the Food Standards Agency, the UK Government
  agreed to phase out the OTMS, replacing it from
  2005 by a vigorous and extensive testing regime
  of all cattle.

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BSE

• Born after the real ban (BARB)
• From August 1996 to 28 November 2004
• UK 99 cases
• Rest of EU (since 1 Jan 1996) 298 cases
• Possible causes
• Inadequate practice/enforcement of controls?
• Maternal/vertical transmission?
• Contamination in calf feed?
• Unknown cause?
• DEFRA has asked Prof William Hill to review its
  work on cases of BSE in cattle born since 1
  August 1996.

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BSE

• BSE controls across the EU
• Essentially similar to the UK controls post-1996,
  plus post-mortem testing of
• suspect cattle over 30 months from January 2001,
• all over 30 months cattle, from 1 July 2001,
• some categories of over 24 months cattle from 1
  July 2001.
• tests mostly being carried out by the Prionics or
  Bio-Rad methods .

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BSE

• Vertical or maternal transmission?
• Supposedly 10 during last six months of
  incubation, by a dubious 1996 assumption based on
  estimation from a flawed experiment started in
  1989 for another purpose.
• More recently reported research (Wrathall et al,
  2002) appears to provide no support for vertical
  transmisssion

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BSE

• BSE risk by countries or regions
• EU Scientific Steering Committee (SSC) and more
  recenly EFSA assessed countries in four
  Categories
• Category I Highly unlikely to present a BSE risk
• Category II Unlikely, but a BSE risk cannot be
  excluded
• Category III Likely to present a BSE risk, even
  if not confirmed, or presenting a low level of
  confirmed BSE risk
• Category IV BSE risk confirmed at a high level
• Note Assessment of risk of BSE being present,
• NOT of level of risk to human health
•  

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BASE

• During 2004 a few atypical cases have been
  described in France, Italy, Belgium, Denmark, The
  Netherlands and Japan, showing prion
  immunopositive amyloid plaques, as opposed to the
  lack of amyloid deposition in typical BSE cases,
  and by a different pattern of regional
  distribution and topology of brain prion
  accumulation.
• This new form has been named bovine amyloidotic
  spongiform encephalopathy (BASE).

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BSE

• Strikingly, the molecular signature of this
  previously undescribed bovine prion was similar
  to that encountered in a distinct subtype of
  sporadic Creutzfeldt-Jakob disease.

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BSE

• BSE and sheep?
• In sheep but masked by scrapie?
• Serious concern since 1996 laboratory
  transmission
• August 1996 similar measures to protect human
  health against BSE in cattle were applied to
  sheep (and goats) in case BSE was present.
• No evidence of presence in Europe BUT.

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BSE

• BSE and sheep? (cont)
• .If present, far more tissues infected than in
  cattle
• If present and behaves in sheep like scrapie,
  both vertical and horizontal transmission,
  infection of pastures
• No satisfactory rapid test to distinguish BSE
  from scrapie in sheep
• Full extent of scrapie in EU flocks is unknown

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BSE

• BSE and sheep? (cont)
• From 1 April 2002, extensive testing for TSEs
  across the EU (560,000 a year, focussing on sheep
  aged over 18 months).
• Extension of the current list of SRMs
• New provisions on culling of scrapie-infected
  flocks
• More use of geno-typing of sheep breeds
• Proposal on identification and traceability
• September 2001 - UK Government contingency plan
  if BSE found in sheep. Worst case scenario"
  could include destruction of the whole 40 million
  national flock.
• June 2002 UK Food standards Agency proposal to
  ban sheep intestines.

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BSE

• BSE and sheep? (cont)
• In 2003 a DEFRA scrapie surveillance survey
  showed that TSE status could not be determined
  for 28 out of 29,201 abattoir sheep) due to
  inconclusive analytical results.

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BSE

• BSE and sheep? (cont)
• In June 2004 DEFRA issues consultation document
  on Contingency plan for the emergence of
  naturally occurring BSE in sheep.
• http//www.defra.gov.uk/corporate/consult/bseinshe
  ep/index.htm

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BSE

• BSE and goats?
• On 12 November 2004 the French General
  Directorate for Food (DGAL) reported that a goat
  was found, when slaughtered in 2002, to exhibit a
  TSE molecularly and biologically compatible with
  BSE. On 28 January 2005 BSE was confirmed. The
  goat was born before the Europe wide ban on MBM.
• .

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BSE

• BSE and goats? (cont)
• Over 140,000 goats have been tested for BSE
  throughout the EU, with only this one case
  discovered. The rest of the infected animal's
  herd of 600 was tested, all with negative
  results. The EU Commission intends increased
  testing of goats.

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BSE

• BSE and goats? (cont)
• EFSA has advised that based on current scientific
  knowledge, goat milk and derived products are
  unlikely to present any risk of TSE contamination
  if the milk comes from healthy animals and is
  assessing whether restrictions are necessary on
  French goat meat.

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BSE

• Transmissible to humans?
• March 1996 UK Government announcement of assumed
  causal connection.
• October 1996 First scientific evidence
  consistent with transmissibility of BSE
  infectivity to at least some humans (possibly to
  all humans but at varying incubation rates).
• Subsequent findings increased likelihood of
  causal connection.

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BSE/vCJD

• Current incidence of vCJD
• As at 8 March 2005 UK - Deaths
• from definite vCJD (confirmed) 106
• From probable vCJD (without neuropathological
  confirmation) 42
• From probable vCJD (neuropathological
  confirmation pending) 1
• Total deaths from definite or probable vCJD
  (as above) 149
• Alive probable vCJD cases still alive 5
• Total number of definite or probable vCJD
  (dead and alive) 154

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BSE/vCJD

• Current incidence of vCJD
• As at 4 February 2005
• Deaths outside UK
• France 8
• Ireland (1 alive, confirmed by brain scan /
  tonsil biopsy) 2
• Italy 1
• Hong Kong 1
• USA (British born) 1
• Canada (spent some time in the UK)
  1
• Italy (alive, confirmed by brain scan / tonsil
  biopsy) 1
• Spain (alive, probable, spent some time in the
  UK) 1
• Japan (visited UK during 1989) 1

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BSE/vCJD

• Current UK incidence of vCJD?
• (per million population aged 10 yrs )

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BSE/vCJD

• The role of MRM?
• Attention focused on MRM as a possible source of
  high titre infectivity in the food chain,
  particularly prior to 1995 when the use of spinal
  column for MRM was banned. Current EU measures
  prohibit MRM from any bovine or ovine bones.

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BSE/vCJD

• The role of MRM?
• A research report prepared for the Food Standards
  Agency, issued 10 October 2002, on Sources of
  bse infectivity attempted retrospectively to
  estimate the uses of MRM in various meat products
  prior to 1996.
• http//www.food.gov.uk/multimedia/pdfs/sources_bse
  _infect.pdf

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BSE/vCJD

• Susceptibility to vCJD
• Assuming causal link between consumption of BSE
  infectivity and vCJD, and millions exposed from
  early 1980s to 1996, why still only ca. 170 cases
  by early 2005?
• In vitro research has found that host prion
  protein that is methionine/methionine homozygous
  at codon 129 is converted to prions more rapidly
  than host prion protein valine/valine homozygous
  at codon 129 (no evidence about heterozygous
  met/val). All of the victims reported prior to
  July 2004 have been met/met homozygous at codon
  129, i.e. suggesting that met/met has a shorter
  incubation period, than val/val or met/val.

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BSE/vCJD

• Susceptibility to vCJD (cont)
• Animal models suggest that human infection with
  BSE-derived prions may not be restricted to a
  single disease phenotype, but may result in
  sporadic CJD-like or novel phenotypes in addition
  to vCJD, with the type of disease experienced
  depending on the genotype of the host source of
  the infection, and the genotype of the recipient.
• (Wadsworth JD et al (2004). Science 2004 Nov 11
  2004)

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vCJD

• Another animal study has shown that transgenic
  mice expressing human PrP methionine 129,
  inoculated with either BSE or vCJD prions, may
  develop the neuropathological and molecular
  phenotype of vCJD, consistent with these diseases
  being caused by the same prion strain.
  Surprisingly, however, BSE transmission to these
  transgenic mice, in addition to producing a
  vCJD-like phenotype, can also result in a
  distinct molecular phenotype that is
  indistinguishable from that of sporadic CJD with
  PrPSc type 2. These data suggest that more than
  one SE-derived prion strain might infect humans
  it is therefore possible that some patients with
  a phenotype consistent with sporadic CJD may have
  a disease arising from BSE exposure.
• Asante et al (2002). EMBO Journal, 21 ( 23),
  6358-6366.

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BSE/vCJD

• Susceptibility to vCJD (cont)
• Codon 129 may not be the only significant
  location. Other research with mice has shown that
  other genes are likely to play an important role
  in susceptibility to infection. Two other genes
  have been located that are involved in
  susceptibility to prion disease in mice. As the
  mouse and human genomes are so similar it is
  almost certain that corresponding genes in humans
  will be found which have the same role to play.
• Possible conclusion?

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BSE/vCJD

• Susceptibility to vCJD (cont)
• Possible conclusion?
• There could up to three variably-susceptible
  genetic groups and at least three sub-groups in
  each. All the reported victims to early July
  2004, all met/met at codon 129, could be in the
  most susceptible genetic sub-group of the most
  susceptible group.
• This wave shows signs of declining but there
  may be several further waves to come.

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vCJDJanuary 1994 December 2004
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BSE/vCJD

• Incidence of vCJD?
• (age vs calendar year)

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BSE/vCJD

• Estimated influence of age on a) risk for
  infection with the variant Creutzfeldt-Jakob
  disease (vCJD) agent and b) risk for death from
  vCJD after infection
• (Barchetti, P (2003). EID serial online 9 (12))

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BSE/vCJD

• Susceptibility to vCJD (cont)
• Following a case in December 2003 of vCJD
  possibly acquired by a 1999 blood transfusion, a
  second case of possible transmission of vCJD from
  person to person via a 1999 blood tranfusion was
  reported Peden, AH et al, (2004), The Lancet,
  264, 527-29.

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BSE/vCJD

• Susceptibility to vCJD (cont)
• A patient in the UK received a blood transfusion
  in 1999 from a donor who later went on to develop
  vCJD. The patient died of causes unrelated to
  vCJD but a post mortem revealed the presence of
  vCJD infectivity in the patient's spleen. This
  was the first instance of vCJD in a person in the
  codon 129 heterozygous (met/val) group.

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BSE/vCJD

• Susceptibility to vCJD (cont)
• This could possibly signal the beginning of a new
  wave of heterozygous met/val cases.
• It also highlights the possibilities of
  iatrogenic person-to-person transmission of vCJD
  from persons silently incubating the disease to
  others via earlier blood transfusions or surgical
  instruments.

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BSE/vCJD

• Transmission by blood
• The two reported cases could have acquired
  infectivity by other means but statistical
  analysis suggests it is more probable it was
  acquired via (non-leucodepleted) blood donated in
  1997 by a person who subsequently developed vCJD
  (there are 13 other persons known to have
  received blood from that donor).

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BSE/vCJD

• Transmission by blood
• Nov 1997 - evidence that pathogenesis of vCJD may
  involve lymphoreticular tissues possibly
  involving circulating lymphocytes, led to UK
  leucodepletion of blood for transfusions and
  purchase of blood supplies from USA.

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BSE/vCJD

• Transmission by blood
• However, in August 2004 research was published
  showing that leucodepletion removed only 42 of
  the initial TSE infectivity from whole blood.
  While further work was needed to identify the
  location of the residual infectivity, it was
  presumed that it is plasma associated.
• Gregori L, (2004). Effectiveness of
  leucoreduction for removal of infectivity of
  transmissible spongiform encephalopathies from
  blood,The Lancet, 264, 529-31.

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vCJD

• How many future cases of vCJD?
• Short-term forecast by CJDSU
• At December 2004, one CJDSU model predicts 6
  deaths (95 CI 2 to 13) in the next 12 months.
• Data may indicate that the epidemic is currently
  in decline rather than on a temporary plateau but
  do not exclude the possibility of further peaks
  in the future.

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vCJD

• How many future cases of vCJD?
• No such thing as the incubation period
• Unknown dates of infection of individuals.
• Age-based susceptibility?
• Dose-response relationship?
• Three main populations (codon 129) with
  differing rates.
• Unknown number of possible genetic
  sub-populations?
• Secondary transmission via blood, surgical
  instruments
• Long-term forecast ?

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vCJD

• Hilton et al (2004) tested samples from 16 703
  patients (14 964 appendicectomies, 1739
  tonsillectomies), approximately 60 of whom were
  from the age group 20-29 years at operation (25
  of samples containing inadequate amounts of
  lymphoid tissue were excluded from final
  analyses), suggests a prevalence of vCJD among UK
  people aged 20-29  of 237 per million.. Three
  appendicectomy samples showed lymphoreticular
  accumulation of prions, giving a estimated
  prevalence of 3/12,674 or 237 per million (95 CI
  49-692 per million). The pattern of
  lymphoreticular accumulation in two of these
  samples was dissimilar from that seen in known
  cases of vCJD. The margin of error for this
  figure is high and the authors stress the need
  for large scale screening of tonsil tissue to
  obtain precise data.
• Hilton DA et al (2004) Prevalence of
  lymphoreticular prion protein
• accumulation in UK tissue samples,Journal of
  Pathology, 202.

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vCJD

• Comment
• Extrapolation from 3 (of which 2 are problematic)
  in 12,674 to the whole population is an
  unwarranted assumption.
• Moreover, we do not know at what stage in the
  long but variable incubation period, infective
  prions become detectable in the tonsils or
  appendix.
• Tonsils removed from 100,000 patients, mostly
  children or teenagers, over the next three years
  may provide a better basis.

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BSE/vCJD

• G Zanusso et al have demonstrated that PrPSc is
  deposited in the neuroepithelium of the olfactory
  mucosa in patients with sporadic CJD, indicating
  that olfactory biopsy may provide diagnostic
  information in living patients. They conclude
  that the olfactory pathway may represent a route
  of infection and a means of spreading prions.
• (NB This has not yet been shown with vCJD)
• G Zanusso et al (2003)NEJM, 348(8),711-719.

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BSE/vCJD

• Main knowledge gaps?
• Despite experimenting with potassium persulphate
  injected into the brain, there is no treatment or
  cure for BSE or vCJD
• despite greater knowledge, the exact mechanisms
  of transmission of infectivity to the central
  nervous system are still insufficiently
  understood
• there is no rapid ante-mortem diagnostic test
  for BSE or vCJD
• it is not known at what stage of incubation
  BSE-incubating cattle would give positive results
  in an ante-mortem test if one existed
•  

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BSE/vCJD

• Main knowledge gaps? (continued)
• it is not known yet whether beef muscle meat or
  milk from infected cattle carry infectivity at
  too low a level to be measured or detected by
  existing methods
• it is not known whether BSE exists in the sheep
  flock
• assuming a causal relationship between vCJD and
  oral consumption of BSE infectivity, it is not
  known what is the infective dose, or whether it
  is a single dose or cumulative.
•  

76
BSE/vCJD

• On 8 January 2003 the EU issued Questions and
  Answers on BSE What is the current state of play
  on BSE in the EU?
• http//www.europa.eu.int/rapid/start/cgi/guesten.k
  sh?p_action.gettxtgtdocMEMO/03/30RAPIDlgEN
  display

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Institute of Food Science TechnologyThe first
of its four purposes is

• to serve the public interest by furthering the
  application of science and technology to all
  aspects of the supply of safe, wholesome,
  nutritious and attractive food, nationally and
  internationally.
• What are the other three?

78
Institute of Food Science TechnologyThe other
three purposes are

• (2) to advance the standing of food science and
  technology, both as a subject and as a
  profession
• (3) to assist members in their career and
  personal development within the profession
• (4) to uphold professional standards of
  competence and integrity

79
Institute of Food Science Technologywww.ifs
t.orgIFST BSE Information Statement
www.ifst.org/hottop5.htm