BSE

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• BSE
• MAD COW DISEASE
• 2005

• Anette Rink, DVM, PhD
• Animal Disease and Food Safety Laboratory
• Nevada Department of Agriculture
• 350 Capitol Hill Avenue
• Reno NV 89502

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Prions

• Proteinaceous infectious particle
• Composed only of protein
• no nucleic acid (DNA or RNA)
• Multiple strains
• Present in non-infected and infected cells
• Host-coded normal cellular protein that becomes
  partially protease-resistant through
  post-translational conformation change

abnormal folding
PrPC
PrPBSE/Sc
Host genetics PrPBSE/Sc
Normal form
BSE form
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Prions, cont.

• Pathologically characterized by the triad
• Spongiform change
• Neuronal loss
• Reactive gliosis
• PrPSc has the ability to convert normal prions
  into its own aberrant structure by a
  template-directed folding mechanism
• PrPSc is non-functional and may deplete the
  brain of the physiological function of PrPC

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Role of PrPC in Copper Homeostasis

• Located at the pre-synaptic membrane
• Most abundant in the CNS but expressed in most
  non-neuronal tissues
• Predominantly pre-synaptic function in synaptic
  transmission and neuronal excitability
• Cu(II) binding at N-terminal octapeptide
• Highly conserved domain amongst species
• Acts as a buffer for Cu(II) in the synaptic cleft

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Neuroprotective Properties of PrPC

• Neuroprotective molecule, response to
  pro-oxidative insults
• Lack of PrPC results in neuronal phenotypes
  sensitive to oxidative stress induced by
  superoxide (O2.-) and H2O2
• PrPC inhibits BAX induced apoptosis in vitro

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Involvement of PrPC in neuronal Ca2 Disturbances

• Loss of normal prion protein is associated with
  disturbance in neuronal calcium homeostasis
• Influences mechanisms of Ca2 release from
  internal ER
• Ca2 is a critical component of signaling
  pathways leading to structural and functional
  neuronal changes
• Modulator of Ca2 flux in response to Cu(II) or
  SOD activity enabling of redox signaling an
  metal dependent biochemical and cellular
  processes

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Schematic representatin of the physiological role
of prion protein (PrPC) in copper homeostasis and
redox signalling.
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Transmissible Spongiform Encephalopathies (TSEs)

• Long incubation period (2-8 years for BSE)
• Progressively debilitating neurological illnesses
• Pathologic changes are confined to the CNS
• Presence of Scrapie-Associated Fibrils (EM)
• Elicit no detectable immune response
• Always fatal

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TSE Agent Theories

• VIRUS
• Unusual biochemical biophysical characteristics
• No nucleic acid identified
• No particle found under electron microscopy
• VIRINO
• Host-derived protein coat (PrP?) small
  non-coding regulatory nucleic acid
• No nucleic acid identified
• No particle found under electron microscopy
• PRION
• Host-coded normal cellular protein that becomes
  partially protease resistant through
  post-translational conformation change
• Most widely accepted theory

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TSEs - Humans

• Creutzfeldt-Jakob Disease (CJD)
• Gerstmann-Straussler-Scheinker Syndrome (GSS)
• Fatal Familial Insomnia (FFI)
• Kuru
• Variant Creutzfeldt-Jakob Disease (vCJD)

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TSEs - Other Animals

• Scrapie
• Sheep and goats
• Known for 250 years
• Chronic Wasting Disease (CWD)
• Captive elk free-ranging deer and elk
• First recognized in deer in 1967
• Transmissible Mink Encephalopathy (TME)
• Mink
• First recognized in mink in 1947
• Feline Spongiform Encephalopathy (FSE)
• Cats
• First recognized in 1990
• Associated with BSE

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BOVINE SPONGIFORM ENCEPHALOPATHY
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Bovine Spongiform Encephalopathy

• Bovine Spongiform Encephalopathy (BSE), commonly
  known as Mad Cow Disease, is a chronic
  degenerative disease affecting the central
  nervous system of cattle and which has been
  linked to a similar disease in humans, variant
  Creutzfedlt-Jakob Disease.

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Origin of BSE

• First case was identified in 1986
• Epidemiologic evidence
• Common source
• Feed containing TSE-contaminated meat and bone
  meal
• sheep with scrapie?
• rendering changes in the 1980s?
• discontinuance of solvent extraction (steam-heat
  treatment)
• amplification
• cattle with previously unidentified TSE?
• cattle were first probably infected in the 1970s
• there are some 35 theories as to the origin of
  BSE in UK cattle

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Clinical Signs

• Incubation (2 to 8 years)
• Gradual deterioration
• Recumbency, death, destruction
• 2 weeks to 6 months
• Neurologic symptoms
• Apprehension, fear, increased startle, or
  depression
• Hyperaesthesia or hyperreflexia
• Muscle fasciculations, tremors, and myoclonus
• Ataxia (incoordination, hypermetria)
• Autonomic dysfunction
• reduced rumination, bradycardia and altered heart
  rhythm
• Progressive weight loss

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Differential Diagnosis

• Rabies
• Milk fever
• Lead poisoning (or other toxin)
• Grass tetany
• Nervous ketosis
• Listeriosis
• Encephalitis
• Thiamine deficiency
• Brain tumor

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Tissue Infectivity
Brain Trigeminal ganglia
Spinal cord Dorsal root ganglia
Retina
Bone marrow
Distal ileum (Small intestine)

• Natural infection
• Experimental infection

NOTE Distribution may involve lymphoreticular
tissues in other species.
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BSE in Great Britain
Total through 2002 183,191 cases
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Italy Japan Israel Finland Slovakia Slovenia Greec
e Austria Czech Republic
First cases of BSE
Liechtenstein
Great Britain
Portugal Switzerland
Denmark Germany Spain
Netherlands Belgium Luxembourg
Canada U. S. ()
France
Ireland
98
90
94
2003
1986
Imported from Canada
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• BSE Incidence Rate (per million cattle gt 2 yrs)

98
99 02 United Kingdom
677 482 248 Portugal
159 199 108 Switzerland 16
59 28 Ireland
21 22 88 France
2 3 21 Belgium
4 2
26 Netherlands 1
1 13
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vCJD Cases(as of 11/3/2003)152 cases
vCJD cases 137 (plus 6 probable)
1 (imported)
vCJD cases - 6
1 (imported)

• vCJD cases - 1

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vCJD BSE
?

• Epidemiology
• Macaques
• Glycoform patterns
• Strain typing
• Transgenic studies

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• EU BSE Surveillance

• CNS cases
• Fallen stock and emergency slaughter
• herdmates of positive cases in some countries
• all bovines to slaughter gt 30 months of age or
  older
• Negative doesn't guarantee lack of infectivity

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Sample Collection
Lesions are usually found in the brainstem.
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Test Methodology

• There is NO live test for BSE!
• Histology
• Immunohistochemistry
• Western Blot
• New tests
• Enfer (High throughput chemiluminescent ELISA -
  3-4 hrs)
• Prionics (modified WB - 8 hrs)
• Biorad (Sandwich Immunoassay (3-4 hrs)
• All need brain

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Diagnosis
BSE-Infected Brain

• Histopathology
• Status spongiosis
• Neuronal vacuolization
• Neuronal necrosis
• Astrocytosis
• Immunohistochemistry
• Finding PrPBSE in damaged areas
• Western Blot
• ELISA
• No live animal test

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BSE US PreventionMeasures

• Import Restrictions - countries with BSE
• July 1989 - live ruminants
• November 1989 - ruminant products
• 1991 - formal regulations
• Import Restrictions - Europe
• December 1997
• January 1998 - interim rule
• all live ruminants and most ruminant products

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BSE - Prevention

• Import Restrictions - Europe
• December 6, 2000 - all MBM, etc. regardless of
  species
• Evaluations of other countries
• South America underway
• Central America
• Asia (Japan)

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SURVEILLANCE

• Field CNS Cases
• VDL data
• CNS condemns at slaughter
• "Downers
• 314,394 (4/12/2005)animals tested since 6/01/2004

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