Viral Infections 2 Flashcards
Viral encephalitis is a complication of
viral meningitis
clinically encephalitic syndrome
Progressive impairment of consciousness, seizures, mood and behavioral changes and focal neurologic signs (memory and orientation)
Causative agents of viral encephalitis
usually arboviruses (files, ticks, spiders, mosquitos) are epidemics,
while others are sporadic – many unknown etiology (treated as viral but agent never determined)
Molecular diagnosis of Viral encephalitis
is difficult (aseptic)
PCR and multiplex PCR
- Multiplexing allows for screening of multiple pathogens simultaneously
- Usually indicative of the infection, but other studies need to be considered (not diagnose unless other - imagining, symptoms, CSF analysis, etc.)
Viral encephalitis CSF analysis
↑ lymphocytes, normal glucose, moderate to ↑ protein
Viral encephalitis neuroimaging
cerebellar lesions, focal lesions in basal ganglia, subependymal, temporal and/or frontal lobe enhancement, white matter abnormalities
no cysts, granulomas, calsifications
Viral encephalitis treatment
primarily supportive
one important exception is HSV encephalitis - acyclovir
most common cause of nonepidemic encephalitis
Herpes viruses
If suspected, all should be started on acyclovir empirically
Who is at risk for viral encephalitis
- Extremes ages (e.g. newborns and elderly)
- Immunosuppression [HIV, orgon transplant, pregnant, steroids]
- Direct animal contact (i.e. live animal markets)
- Recreational activities that put you in contact with insects
- Vaccination status
- Geographical area and season
Herpes viruses
radiculitis
Radiculitis or radicular pain is pain that radiates along the path of a specific nerve as the response of pressure on the nerve root.
Sequelae
a condition which is the consequence of a previous disease or injury.
“the long-term sequelae of infection”
Ways HSV-1 can get into the CNS
1) Retrograde and anterograde transport through nerves (nerve hopping)
2) Infections of epithelial cells
- Most viruses that can cross the CNS barriers can cross the placenta
- All herpesviruses can cause CNS infections during primary infection or following reactivation from a latent state
Most common forms of Arbovirus in the US
Arbovirus reservoirs
Birds and other animals (such as horses) are the usual reservoir for the infection, and they are involved in its spread
Also seasonal, when mosquito breeding reaches its peak
Arbovirus encephalitis patients
Rabies historically
One of the oldest viruses in the historical record
Described in texts from early human civilizations
‘Rabies’ comes from Sanskrit word ‘rabhas’ which means “madness” (in 4,000 year old texts)
Rabies mortality
100% mortality in unvaccinated or untreated individuals
Rabies is usually acquired from
dog, bat, or other wild terrestrial animal bite
Incubation period of rabies
from 5 days to >6 months
varies dramatically related to how get into CNS - long way toe to head, short way neck to head
rabies CNS movement
Late stages of rabies
change tropism (now antigrade) - forward
movement to infect acinar cells of the salivary gland - saliva becomes the vector
fer of water - because saliva now vector - not want to wash away virus
Primary manifestation is
encephalitic syndrome:
behavioral alterations (aggressiveness, hydrophobia),
followed by dementia-like state with quadriparesis (weakness of all 4 limbs) then death
once show symptoms - death in days
rabies inflammation
Very little, yet pathology is very aggressive - negri bodies
rabies Histopathologic hallmark
Negri bodies
only seen postmortem
viral replication factories - interfeer with neuronal functioning
