L84 Flashcards
Define encephalitis
Inflam of BRAIN
Define meningo-encephalitis
Inflam meninges + brain
Define encephalo-myelitis
Inflam of brain + spinal cord
Encephalitis presenting symptoms
“Sleepy or acting weird”
Changes in consciousness
Changes in personality
Ataxia
Viral causes of encephalitis (usually not 1ary presentation - more likely a 2ary complication)
HSV
Other herpes viruses
Enteroviruses
Measles, mumps, JC
How does West Nile present?
- 80% asymptomatic
- AMS
Fever
Asymmetrical weakness w/ decreased reflexes of all extremities
West Nile virus family & genome
Flavi virus (Flavored corona) \+ssRNA - Cytoplasmic replication Icosahedral Enveloped - buds out
West Nile vector vs resevoir
Mosquito = vector Reservoir = birds
West Nile pathogenesis
Mosquito bites
Infects DCs at skin
Viremia = when get symptoms
CNS penetration + neuron invasion
What part of immune system controls West Nile?
Everything!
Need IFN + Ab + cell mediated
What genetic variant increases susceptibility to severe presentations of West Nile?
CCR5 delta 32
Butttt gives HIV resistance….
HIV resistance is better than the downsides of getting West Nile
What is the most common viral cause of encephalitis in the US?
West Nile
Esp summer & fall when mosquitoes are active
West Nile vaccine?
Nope
What is the “home grown West Nile”? Describe presentation.
St. Louis Encephalitis
Meningoencephalitis but without the paralysis of West Nile
What is the viral family of Eastern & Western Equine viruses? Therefore, describe genome.
Toga
+ssRNA - cytoplasmic replication
Icosahedral
Enveloped - buds
Describe the steps in which E&W Equine genome is transcribed.
\+ssRNA parent Make non-structural proteins - Including RNA pol RNA pol makes -ssRNA from +parent -ssRNA codes for 1. +ssRNA for new viruses 2. mRNA --> codes for structural proteins
+ssRNA –> structural –> RNA pol & -ssRNA –> +ssRNA & mRNA –> structural proteins
Presentation of East Equine virus.
Acute: non-specific fever illness
2-3 days = encephalitis
If you progress to encephalitis, MUCH higher mortality w/ eastern
Presentation of West Equine virus.
Asymptomatic or mild fever illness
Small grp develop encephalitis
Low mortality
Equine resevoir vs vector
Horses + birds = reservoir
Transmitted by mosquitoes
Buzzword for Eastern vs Western
Eastern = USA swamps Western = USA irrigation sites
What is the family and genome for La Crosse aka California viruses?
Bunya (Bring pol...) -ssRNA - cytoplasm replication *Brings own RNA pol* Helical capsid Enveloped
California virus presentation
Kids: neuroinvasive disease
I.e. seizures
Likely to recover w/o long term complications but scary in the short term
Least severe of all the mosquito borne encephalitis
How is California virus transmitted? Where?
Triseriatus mosquitoes
Live in hollowed out trees along forest edges
Midwest & south USA
Rabies - genome + family
Rhabdo
- ss RNA
Helical capsid
Enveloped
Rabies pathogenesis
Bite from rabid animal
Into muscle cells - SLOW replication - months
Eventually enters motor nerve
Retrograde
FAST replication - spreads throughout CNS
Peripheral dissemination
Once rabies gets to the CNS, what are the 2 types of damage that can occur - how does each determine symptomatic presentation?
1. Encephalopathic Dysregulation of NT = excitatory state Hyperactivity/agitated before... 2. Paralytic Ascending flaccid paralysis Neuron necrosis = coma
What might you see in muscle cells infected with rabies on histo?
Negri bodies = accumulation of M protein = matrix protein as virus replicates and buds out
Immune response to rabies
Abs vs G protein = attachment to muscle cells
Too slow - don’t kick in until in CNS
What is the most common rabies host in the US vs worldwide?
US = feral cats
World = dogs
- Aka if someone in your clinic has rabies from a dog, they got it outside the US
Always be worried about bats, raccoons, etx
Symptoms of rabies
Numbness at bite site Diplopia N&V CN palsy Unsteady gait
Rabies incubation
LONG b/c localized
30-90 days
What’s a weird symptoms that is a clue for rabies?
Fear of water
Suggests in encephalopathic stage of acute neuro disease
Test for rabies
CSR culture
DFA stain neck skin biopsy
Treat rabies
Gotta do it in the WINDOW period - when still localized in skin
2 parts:
+ rabies Ig
+ vaccine - must give IM in DELTOID
