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CNSLF Micro - Viral Infections + Prions in CNS (iv) (Transmissible…
CNSLF Micro - Viral Infections + Prions in CNS (iv)
Chronic CNS Infections
SSPE
persistent measles virus infection in the CNS, develops yrs after original infection
rare: 1 in 1 million who had measles in 1st 2 yrs of life
behavioural + intellectual deterioration, seizures, fatal outcome
host normal - not immunosuppressed
HIV encephalopathy
immunosuppressed host
convulsions, dementia, motor disorders
PML
uncommon OI caused by reactivation of JC virus resulting in demyelination
no tx: reduce immunosuppression
Transmissible spongiform encephalopathy (TSE)
fatal degenerative brain disease
Creutzfeldt Jakob Disease (CJD)
types
classic aka sporadic/familial
mutation of prion protein
presents in late middle age (death in 60s)
rapid (4 months to death)
variant
ingestion of BSE via meat or recipient of contaminated blood products)
younger (20s)
slower progression (14 months to death)
iatrogenic (rare - most dura mater grafts or human pit hormone)
tissue distribution of prion protein varies in classic (brain + cord) vs variant (brain, eyes, tonsils, cord, thymus, spleen, adrenal, LNs, appendix, rectum)
dx
MRI brain changes may be helpful
CSF 14-3-3 protein (non-specific)
dxed conclusively by histological exam @ PM: spongiform changes, amyloid plaques, prion proteins
no proven effective tx
Prevention
protecting blood supply
protecting food supply (e.g. ban feeding bonemeal to cattle)
protect HCWs from inoculation injuries
appropriate management of surgical instruments
autoclaving highly effective @ killing microorganisms but not completely effective against prions
surgical instruments used on brain, cord or eye (high risk surgeries) if sufferer should be never reused + destroyed by incineration
okay to reuse after low risk procedures (other sites) after cleaning + autoclaving using standard protocol
occur in humans + some animal species
incubation period of months to yrs
gradual increase in severity leading to death
they don't evoke an immune response
causative agent is a protease resistant protein which accumulates in brain
altered form of natural occurring prion protein (PRP) present in human + animal rain tissue
the altered prion proteins are resistant to inactivation by standard chemical, thermal + other means of inactivating micro-organisms