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47 Cards in this Set
- Front
- Back
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Scrapie
-is a type of |
-Prototype Transmissible Spongiform Encephalopathy (TSE)
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Transmissible Spongiform Encephalopathy
-other diseases |
-Scrapie
-BSE -Transmissible mink encephalopathy -chronic wasting disease -Creutzfeldt-Jakob disease -Kuru |
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TSE
-characteristics |
-prolonged incubation
-progressive, debilitating, neurologic disease -no immune response -always fatal -widespread vacuolation in the brain -transmissible -some inherited |
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TSE
-cause |
-Prions
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Prions
-definition |
-proteinaceous infectious particles that lack nucleic acid
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TSE
-transmission requirements |
-protein
-prion protein (misfolded cellular protein) -normal cellular prion protein |
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Where is the highest expression of normal prion protein?
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-neurons
-lymphocytes |
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Scrapie Associated Fibrils
-definition |
-scrapie prion proteins are resistant to degradation by proteases and accumulate in the brain forming aggregates
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Conformational change of Prions from normal prion proteins to scrapie prion proteins
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-normal prions = alpha-helices
-scrapie prions = beta-pleated sheets (amyloid) |
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TSE
-proposed pathogenesis |
-scrapie prion acts as a template that causes normal prion protein to misfold to scrapie prion protein
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Scrapie
-what is necessary for transmission and susceptibility |
-transmission: scrapie prion protein
-susceptibility: PrP gene |
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TSE
-what is the role of normal prion protein? |
-unknown
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TSE
-prion inactivation |
Resistant to:
-UV light -radiation -ionization -disinfectants -heat (wet heat is more effective than dry) Recommendations to inactivate: -porous load autoclaving (>18 min) -bleach 40% 1 hr -2N NaOH for 1 hr -Autoclave at 15 psi on 1N NaOH |
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Biological Strain Type
-definition |
-transmission characteristics in inbred mice
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Scrapie
-natural host |
-sheep
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Scrapie
-susceptible animals |
-goats (rare)
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Scrapie
-transmission |
Horizontal transmission:
-oral -placental fluids -tissues rich in prions Environmental Contamination Mother to Offspring at or shortly after birth |
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Scrapie
-what is the most important method of transmission |
-mother to offspring at or shortly after birth
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Scrapie
-distribution |
-australia and new zealand are free
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Scrapie
-pathogenesis |
-oral infection by scrapie prion
-replication in tonsils, pharyngeal lymph nodes, peyer's patches, spleen, lymphoid tissue -spread to the spinal cord via autonomic nerves -spread to brain via vagus nerve -lag period in CNS -development of clinical signs in CNS -death |
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Scrapie
-how is resistance determined in the US |
-amino acids coded at codons 171 and 136
-171 is the most important |
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Scrapie
-main breed effected in the US |
-Suffolk 85%
-white faced breeds highly sisceptible |
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Scrapie
-why are Suffolk sheep most affected? |
-homozygous for glutamine (Q) at codon 171
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Scrapie
-Homozygous RR sheep |
-completely resistant to scrapie
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Scrapie
-Heterozygous QR sheep |
-resistant to classical Scrapie
-prion accumulation only in neural tissue -believed to not naturally transmit Scrapie |
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Scrapie
-factors affecting the onset of clinical signs |
-age of infection
-infective dose -genetics -scrapie strain |
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Scrapie
-clinical signs |
-rare before 2 yrs old
-ataxia -swaying of hind limbs -high stepping -abnormal head carriage -behavioral changes -tremors -pruritis --> rub against abjects (scrapie) -chew coat -lumbar scratch elicits chewing response -weight loss while eating -emaciation -death |
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Scrapie
-gross lesions |
-self-trauma
-emaciation |
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Scrapie
-microscopic changes |
-vacuolation in neurons and neuropil in midbrain, brain stem, spinal cord
-neuronal degeneration -astrocytosis -amyloid (some cases) -NO inflammation |
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Scrapie
-diagnostic tests |
-immunoperoxidase staining
-ELISA -western blot -ID of scrapie associated fibrils in brain tissue by EM |
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Scrapie
-diagnostic samples from live sheep |
-3rd eyelid
-rectal mucosal biopsies containing lymphoid tissue |
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Scrapie
-diagnostic samples from dead sheep |
-obex
-tonsil -retropharyngeal LNs |
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Scrapie
-prevention and control |
-all sheep moved must be identified using appropriate ear tags
-monitoring by sample collection at slaughter to ID infected herds -positive sheep are slaughtered -test unaffected herd mates to determine susceptibility -homozygous QQ sheep are slaughtered -Eliminate scrapie with homozygous resistant rams and retain only their offspring |
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Scrapie
-Codon 171 amino acids |
-Glutamine (Q) - susceptibility
-Arginine (R) - Resistance -Histamine (H) = Q |
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Scrapie
-Codon 136 amino acids |
-Valine (V) - susceptibility
-Arginine (A) - resistance -only look at in QR sheep from 171 |
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Scrapie
-3 steps for national genetic flock clean up plan |
-determine genotype of sheep in infected herd
-remove or restrict movement of susceptible genotypes -place flock under surveillance for 5 yrs |
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Chronic Wasting Disease
-cause |
-prions
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Chronic Wasting disease
-animals affected |
Cervids
-deer -elk -moose Adults 17 months to 15 yrs |
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Chronic Wasting Disease
-distribution |
mostly colorado/wyoming area of US
-some other areas of US and Canada as well |
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Chronic Wasting Disease
-modes of transmission |
-animal-to-animal
-environment -possible insect transmission |
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Chronic Wasting Disease
-infected bodily fluids |
-blood
-saliva -all body fluids considered potentially infective |
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Chronic Wasting Disease
-clinical signs |
-progressive weight loss --> emaciation --> death
-head tremors -ataxia wide based stance -behavioral change -listlessness -less herd interaction -PU/PD -hypersalivation -aspiration pneumonia -death |
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Chronic Wasting Disease
-gross lesions |
-emaciation
-aspiration pneumonia |
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Chronic Wasting Disease
-diagnosis |
-same as Scrapie
-must test obex if brain is to be reported as negative (western blot) -ELISA for retropharyngeal lymph nodes only in wild herds -positive ELISA must be confirmed with Western Blot |
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Chronic Wasting Disease
-how to keep samples for ELISA and Western Blot |
-ELISA: chilled
-Western Blot: 10% formalin |
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Chronic Wasting Disease
-control in commercial game deer |
-double fencing
-buy from known free herds -depopulate or quarantine infected herd -don't restock contaminated land -test all animals who die for 5 yrs |
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Chronic Wasting Disease
-control in wild cervids |
-surveillance
-ban feeding and translocation -localized depopulation except in endemic areas |
