Viral Encephalitis Flashcards
name some viral causes of encephalitis ?
Enterovirus – common cause (Non polio enterovirus – coxsackies, echo)
HSV – common cause – treat with aciclovir
Measles, Mumps – rare in the US
JC Virus – seen in immunocompromised patients
West Nile Virus St. Louis Virus La Crosse Virus Eastern Equine Encephalitis Virus (EEEV) Western Equine Encephalitis Virus (WEEV) Rabies
West Nile VIrus
Virology - what family
what is the reservoir?
how is it transmitted ?
Flavivirus
Enveloped
Positive sense ssRNA
birds are the common reservoir
Trasnmitted by Culex Mosquitoes
West Nile Virus –
Describe the pathogenesis
immune response
what mutation confers increased susceptibility
- Bitten by mosquito
- Dendritic cells in skin –> Viremia –>CNS penetration/neuronal invasion
Immunity: Abs, CMI, IFNs;
CCR5 Delta 32 – increased neuroinvasive disease
West Nile –
clinical manifestations
what % have encephmyelitis?
what % die?
Largely asymptomatic
~ 80% Most people have no symptoms
20% develop non specific febrile illness
1% encephalitis or encephamyelitis
10% of persons with Nuero-invasive disease will die
What are the signs and Symptoms of Encephalitis?
1) Depressed or Altered conscioussness, changes n personality, or ataxis
PLUS – Fever, Sz, focal neuro abnormalities,
Long term – comas, vegetativ states, spasticity; paresis;
Treatment and prevetnion of WNV?
None
avoid mosquito bites
no vaccine
St. Louis Encephalitis Virus
Virology? what family?
Flavivirus
Fever, , meningoencephalits
Very similar to WNV, but much lower incidence
Eastern and Western Equine Encephalitis Virus
Virology: what family?
Togavirus (like rubella)
Enveloped
Icosohedral capsid
Non segmented ss RNA +
Clinical manifestations of eastern and western equine encephalitis virus,
how are they different?
Eastern EEV –
Abrupt chills, fevers, mailiase, arthalgia, myalgia
5% of patients – encephalitis —
Mortality or permanent disability in MOST patients with encephalitis
WEEV
Encephalitis –
Lower mortality and lower permanent disability
EEEV and WEEV –epidemiology: where do they occur
how many Nuero invasive cases per year ?
EEEV – wetlands of the eastern and southern USA
WEEV – midwest; a/w agricultural irrigation
0-40 cases per year
Lacrosse Virus –
what family is it in?
Clinical features?
Epidemiology? who are the hosts, how is it trasmitted?
Bunyaviridae (hantavirus)
- Negative sense ss RNA
N/V lethergy
Nueroinvasive disease in kids
Sz
Rare mortality
Epi:
Hosts: small mammals (squirrels, chipmunks)
Transmit: Aedes mosquito –
Midwest wooded areas
Rabies Virus –
virology? – what family is it in?
describe the shape?
Rhabdoviridae
Enveloped
Helical
negative sense SS RNA
rabies virus –
what proteins does the genome encode?
describe the lifecyle
G - glycoprotein; important for binding; immunoantigen
M – matrix protein
N– nucleoprotein
P – Phosphoprotein
L - Polymerase
G anchors –> endo –> fusion –> transcription to mRNA –> translation
when enough N is made, switch to replication
Coat negative strnds in NPLM
released by budding
Rabies VIrus
Pathogenesis
After bit – enters muscle cell
replicates very slowly
Reaches motor nerve –
G protien binds ACH
Retrograde axonal transport
replicates and spreads rapidly through CNS (neuronal necrosis vs dysregulation of NTs)
almost 100% Fatal if it progresses this far
What is the pathognomonic histologic finding for rabid virus ?
Negri bodies
