Virology Flashcards
Defn aseptic meningitis
Clinical/lab evidence of meningitis with neg bacterial culture
Viral injury to CNS occurs by either
Cytolitic replication
Immunopathology
Common causes of aseptic meningitis
Enteroviruses
Mumps
(RARE -HSV2)
Histology of post infectious encephalomyelitis (ADEM)
Lymphocytic infiltrate
Peri vascular cuffing of adjacent blood vessels
Lesions seen in ADEM
White matter lesions
NB molecular mimicry to myelin (T cell destroys)
Cause of post infectious encephalomyelitis
Almost all viruses
Post vaccine
Lesions seen in encephalitis
Grey matter lesions
Signs in encephalitis
Fever Drowsy Decreased consciousness Focal signs Confusion Convulsions
Common causes of encephalitis
Herpes simplex
Rabies
Arboviridae
Pathogenesis of acute flaccid paralysis
Enter via gut. Bloodstream. Cell bodies of motor neurons = grey matter lesions
Spread of measles
Reap droplets
Vaccine for measles
Live attenuated vaccine
Not earlier than 9 months = mother IgG prevents vaccine replication
Who doesn’t get measles vaccine
Pregnant
Severely immunocomprimsed
(<1 year)
Possible syndromes from measles in CNS
Acute Measles Post infectious encephalitis
Measles inclusion bodies (immunocomprimsed)
SSPE
Spread of mumps
Resp droplets
Distinguishing feature of mumps
Parotitis
Period of aseptic meningitis in relation to parotitis in mumps
One week before to three weeks after
What may follow aseptic meningitis in mumps
Encephalitis
Vaccine for mumps
Live attenuated
Not in SA
What is seen in 25% post pubertal men in mumps
Orchitis (may lead to infertility)
How to diagnose mumps
Serology
Culture saliva/urine
PCR
Is it useful to do PCR in post infectious encephalomyelitis
No. Immune reaction so no virus in CSF
Spread of enteroviruses
Fecal oral
What do enteroviruses most commonly cause in CNS
Aseptic meningitis
Acute flaccid paralysis
Three clinical outcomes of polio
Asymptomatic
Minor febrile illness
Major illness - Acute flaccid paralysis
- aseptic meningitis
- respiratory paralysis
Diagnosis of polio
PCR
Culture
Vaccine for polio
Live attenuated oral (IgA) Formalin Inactivated (IgG)
Why six doses of polio virus vaccine
Only one strain ‘takes’ each time
Four ways viruses can enter CNS
Anterograde neuronal transport
Retrograde neuronal transport (rabies, HSV)
Trojan horse by lymphocyte/ macs cell lines (west Nile, HIV)
Infection of endothelium in blood vessels in BBB
Post exposure prophylaxis for rabies
Rabies Ab
Rabies vaccine
Lethal syndrome that may develop after influenza
Reye’s syndrome
<18
Aspirin ingestion
Pathogenesis of post infectious encephalomyelitis
Following viral infection, T cell confuse myelin in CNS with viral antigen epitope = molecular mimicry.
White cell lesions in CNS
How does the immune system cause damage in viral infections?
- cytotoxic T cells attack virus infected cells
- antibody binding to infected cell attracts NK cells and triggers complement mediated cell lysis
- antigen-antibody complexes cause inflammatory reactions
Pathogenesis of post-infectious encephalomyelitis
T cells confuse the myelin in the brain with viral antigen epitope
3 most common causes of uncomplicated viral meningitis
- mumps
- HSV
- enteroviruses
2 polio vaccines
OPV - live attenuated - at birth
IPV - killed - 6/10/14/18 weeks
Post- exposure prophylaxis after dog bite
- tetanus toxoid
- wash with soap
- antibodies into wound/deltoid
- vaccine days 0,3,7,14
- again on day 28 if immunocomp
High risk HPV types
- 16,18,31,33,35
Virus causing progressive multifocal leukoenceohalopathy
JC virus
Who is at risk of PML.
Immunocomp patients
3 forms of measles in the CNS
- acute measles post-infectious encephalitis (immunocompetent, AI,days to weeks, varied outcome)
- measles inclusion body encephalitis (immunocomp, weeks to months, virus present, fatal)
- subacute sclerosing panencephalitis (immunocompetent, years, slow progression to death)
Difference between PIEM and GBS
GBS is demyelination of the peripheral nerves
PIEM is due to demyelination if the CNS
