(32) Viruses Affecting the CNS Flashcards
What levels for the following labs suggest bacterial etiology of meningitis? CSF glc CSF protein CSF WBC CSF neutrophil
CSF glc < 34
CSF protein > 220
CSF WBC > 2000
CSF neutrophil > 1180
only need 1 of the above to make Dx
presentation of viral meningitis
fever, malaise, neck stiffness, low back pain
etiologies of viral meningitis
80% from enterovirus (Echo, Coxsackie, enterovirus 71)
10% from Mumps (prior to MMR vaccine)
recurrent aseptic meningitis is due to
HSV-2 (genital herpes)
HIV and VZV cause ______ meningitis
recurrent
What are the 3 etiologies of viral encephalitis
arbovirus (West Nile, St louis, La Crosse)
enterovirus
HSV-1
clinical course of viral enchephalitis
preodromal URT infection fever headache letharghy parenchymal involvement = seizures, coma, death
what is the treatment for HSV-1 encephalitis
acyclovir
what is the treatment for CMV encephalitis
gancyclovir
HSV encephalitis is more common in (acute, reactivation, or latent) infection
reactivation of latent
Where in the brain does HSV encephalitis characteristically cause damage
temporal lobe (due to necrosis)
What are the mosquito borne encephalitis viruses?
Flaviviruses = west nile and st. louis
alphaviruses = eastern, western, and venezuelean equine
bunyavirus = California encephalitis, la crosse virus
What are the animal transmitted encephalitis viruses?
rhabdovirus (rabies) and arenavirus (LCMV = lymphocytic choriomengingitis virus)
structures of flavivirus (West nile and St. louis)
enveloped + RNA
describe the replication cycle of the flavivirus
enter via receptor mediated endocytosis. low pH allows membrane fusion and then uncoating. + strand translated into Rdrp. + strand is used to make - strand which is then used to make progeny. virion assembly and budding
all flaviviruses are transmitted by ____
insect vectors
what are flaviviruses that cause dz in US
west nile, st louis, yellow fever, dengue (usually traveled abroad)
length of incubation prd for SLE
4 - 21 days
how long after URT/primary viremia will neurological symptoms of SLE present
1-4 days
describe the transmission cycle of the west nile virus
bird reservoir and mosquito vector to infect humans
distinguishing characteristic/presenting signs and symptoms of west nile infection
rash and lymphadenopathy
most significant etiology of arboviral encephalitis
Japanese encephalitis virus
structure of togavirus (alphavirus)
enveloped, non-segmented + RNA
vector for alphaviruses
mosquito
what determines the severity of the dz in alphavirus infections?
dept on dose and age of pt
describe the typical dz progression of an alphavirus infection
fever for 7 to 11 days then resolution of abrupt onset of encephalitis with vomitting, dizzynes, confusion. 2-3 days and person becomes comatose and dies
describe the structure of the bunyaviruses
enveloped, ss - RNA
what is the most common cause of arboviral induced pediatric encephalitis in US
La crosse virus
structure of rabies virus
enveloped, nonsegmented - RNA
bullet shaped morphology
describe the replication cycle of rhabdoviridae
endocytosed and used glycoprotein to attach at fuse (pH dept process) Rdrp is packaged in virion with - RNA so when uncoated a + RNA is made. This RNA serves as the template for the progeny -RNA and the code for the RDRP to be made to be packaged with the - RNA
Why does rabies virus characteristically involve the CNS
the attatchement glycoprotein shows neurotrophism
during the final stages of rabies, high conc of virus can be found in what organ
salivary glands
how is rabies transmitted
animal bite, sratch, lick
what is the incubation period for rabies
usually 2-3 mos (BUT can be as short as 1 week)
what determines the incubation period for rabies
proximity of bite to CNS
Describe the progression of the dz caused by rabies
- prodromal = 2-10 days after exposure in which pts has fever, malase, and headache
- neurologic phase = mos to years after exposure in which the pt gets anxiety, agitation (when enchephalitis develops), paralysis
- coma and death 2-7 days after acute neuro phase and can last 3 days to ~ 1 month
treatment after bite from rabies infected animal
2qw wound and admin human anti-rabies Ig to wound and admin rabies vacine IM on days 0, 3, 7, 14, 28
what type of vaccine is rabies virus
inactivated
describe the structure of LCMV
enveloped, segmented, ambisense RNA (2 segements)
describe the replication scheme of LCMV
endocytosed
NP portion of S strand is replicated first then GP then L portion of L strand
?????
how is arena virus transmitted`
inhalation of aerosolized rodent excreta and saliva
describe the phases of LCMV/arenavirus dz progression
prodrome of fever headache, N/V. 10 days later get aseptic meningitis (rarely fatal)
