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50 Cards in this Set

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all of the arbo virus are spread by what? what is the exception. when are these viruses spread

mosquitoes, except colorado TICK fever

**spread in summer/fall

Arbovirus means ARthropodBOrn
what diseases so arbovirus cause? how do we treat
1. Aseptic meningitis- fever, HA, stiff neck, mild disease

2. Encephalitis- seizure, altered mental status, pararlysis

we CANOT combat the arbovirus, we can only prevent (wear bug spray, stay inside etc)
3. meningoencephalitis- combination
what are some general features of arbovirus (genome, structure, transmission, hosts)
enveloped, inactivated by solvents
from mosquito bite

infect lots of things like birds and small animals, we are usually dead end hosts

**the arbo are are transmitted the same but lots of vairation in structure and gemone expression/replication
ok so an arbo can cause meningitis, encephalitis or a combination, what determiens the outcome
1. specific viral agent
age of pt
3. extent of encephalitis

**mostly infections are subclinnical- flu like with no CNS.
**in severe causes there is sudden fever, vomit, HA, vertigo etc. cant recover or not- 50/50
what is recovery after arbovirus
ehh, you might you might not

Kids- deafness, psychomotor diffuculty, learning disability

**recall polio- paralysis worst at 2-3 days then recover was max at 6 weeks
how is arbovirus dx
ehh, often its not. (not the specific virus)

**epidemics create high index of suspicison

**IgM AB detection- test CSF or serum with elisa
tell me about IgM AB capture with arbovirus
use ELISA, lots of cross talk

**test CSF is best but perhaps can just get serum (serum + may not indicate whats going on it spinal cord)

**test for AB EARLY! and look for 4x increase in titer
ok so we can run IgM ELISA to test for arbovirus adn look for 4x increase in titer, what about viral cultures
not usually done for arbo virus

**collect specimen early
for what arbovirus is an indirect AB test good?
colorado tick fever, (common in transfusions)

BHK21 cells are infected and stained with AB
other than IgM elisa and indirect AB test, what else can be dont to detect arbovirus
reverse transcriptase PCR

**keep in mind only a minority of cases have hte exact virus ID
how are arboviruss monitored In the environment
mosquite trapping (or bird but its harder)

**when its high in them its likely a human will get it
what are hte dx clues for an arbovirus

how do we treat
time- season (late summer/fall)
place- endemic area
person- 90% its a person under 30

**no tx for arbovirus (viral meningoencephalitis) supportive measures only
arbovirus encephalitis resevoire
zoonotic diseases, WIDE resevoire- mostly mosquitoes, vertebrates, rodents, birds, amphibians (crocidile)

humans are typically a dead end host
what type of virus uses arthropod as a TRUE biological vector

Virus infects and multiplies in gut, disseminates in the hemolymph, and ultimately establishes a persistent infection in the salivary glands where it may be transmitted. infected vestor shows no disease nad no amplification of virus occurs here
tell me about arbovirus amplificaiton
wont happen in the vector BUT>..

say there is a bird nad mosquitoes feed on it. the bird is uninfected and gets bit by an infected mostuito, the bird is now infected and can pass the virus along to uninfected mosquitoes that feed on that bird
arbo epidemics are associated with what
seasionality- late summer/fall. changes each year

**large vector pops--> increased disease
describe the sylvatic cycle of arbo virus
from a mosquito to a bord and back and forth- the mostioto accidently passes it to us. we are dead end host for the virus.

*we are accidental host, amplification will NOT occur in us (contrast to urban where a human can pass back to mosquito)
what is the urban cycle associated with arbo virus
lots of humans and lots of mosquitoes

**humans have enough viremia to sustain life cycle. human--> mosquito--> human. st louis encephalitis, yellow fever

**contrast to sylavatic cycle where humans were dead end
what type of cycle do ellow fever and st louis encephalitis have
urban- humans have sustained viremia and are part of cycle

**contrast to sylvatic where humans are dead end accidnetal hosts
can we prevent arbo virus
not with vaccine- they are in SO many other things than humans so vaccine wont work

**best thing to prevent it to stop chain of transmission

1. kill the vector
2. avoid exposure
3. immunization of horse/pig NON HUMAN AMPLIFYING HOSTS
so we prevent arbo we can control arthropod vectors, prevent exposure and vaccinate amplifying hosts t or F
what is the family, structure, etc of arbo

how it inhibits host
todaviridae group (toga= cloak= enveloped)
ss + RNA
Hemagluttinin is in envelope
Repliacated in cytoplasm (like LCMV- rodents)

causes pathology in host bc it stops translation of mRNA
what are hte 2 basic groups of hte togavirus
togavirus- arbo

1. Alpha

2. Flavivirus
St louis, West Nile, Yellow fever

**LOTS of cross talk, IgM tests are hard to intrepret
wht virus causes california encephalitis

ss - RNA
envelope (all arbo)
tell me about EEE (eastern equine encephalitis)

Eastern US (N and S)

summer fall (June-Oct)

**in Fl its all year!

SUPER deadly but not very common

**less than 15 yo, older than 55


**often inapperant
a person from Rhode Island got encephalitis in July. The pt was 10 and his 80 yo granddad got it to after fishing in a swamp

which one?
what vector? resevoire?
EEE- eastern, fall/summer, extremes of age

Resevoir: horse, bird
Vector: mosquito* needs bridge vector bc the mosquite that spreads it is only a bird one

which arbo has a high case fatality rate,

vector, resevoire

1. old, young, in the east, swamp, summer/fall
2. vector- mosquito (bridge vector) resevoire- horse, bird

**young children have better survival than adults

**concern that more mosquite spp will increase infections
which encephalitis wiped out turkey farms
EEE- old and young, swams, horse/bird/mosquite.eastern, fall/summer
whats WEE

west of Mississippi, irrigated pastures, flooded grounds (no fish)
Summer Fall: wont see it then it explodes
Resevoire: bird, horse, small mammal
Vector: mosquito
KIDS under 10 (most often subclinical)
what disease affects kids in a burst where there are flooded pastures

mosquito- bird, horse, small mammal
in what disease are horses huge in the amplification process nad we shoudl prbly vaccineate them
Venezuelan Equine Encephalitis

**benign usually but with outbreaks with apparent disease. most human VEE have apparent disease

**disease of "place" central/sounth america, texas, everglades.


**spread until the horse dies
whats VEE
ususally benign but thwn a horse gets it it can be HUGE for amplification. ppl get it til the horse dies

infection of place- texas, everglades, central/S america

**horse is amplifier
what is venezuelan Equine Encephalitis
benign usually- can have outbreaks
Rapid spread til horses are dead or we get dry enough weather that the mosquitoes die

Central/S america, US everglades, texas

**horses are amplifying hosts

**most human VEE infections result in apparent disease
what is st louis encephalitis

where, when?

wide distrubution, conc in Midwest US and california (Oh/MS river basin, gulf coast)

Summer Fall (aug/sept)

can have seasons with HIGE numbers of outbreaks and then just a few

aaffects adults over 40

**bird resevoire, mosquito vector
what encephalitis effects adults over 40 in the summer where there is lots of agriculture and ppl are low SES and hand out outside inthe evening
st louis encephalitis

Bird resevoire , mosquite vector
if you have a honkey tonk 40 yo who likes birds and hangs out outside in the summer evenings in your home in OH/MS what encephalitis are you at risk for
st louis

low ses, hang outside in evening, agriculture places (OH/MS/CA)
tell me a bit about west nile virus

who is at greatest risk
common in US
largest risk is old ppl (>50)
not common, its an EMERGING disease (not known how long its been here)

**neuroinvasive paralytic syndrome simliar to poliomylitis
west nile gives encephalitis simliar to what other neuroinvasive disease
what is the west nile virus transmission cycle
bird resevoir --> mosquito vector

**the mostoito can then infect us and livestock as indicental infections
how is west nile dx
IgM ELISA with serum or CSF- lots of cross reaction with St Louis or Yellow fever

**plaque reduction neurtralization test may be used to confirm
what % of west nile infections result in disease

*8what predisposes you to getting the bad effects

About 1:150 total infections result in severe neurological (neuro-invasive) disease

Most important predictive factors for severe disease/death is advanced age (>50 years) or immune system dysfunction
The flaccid paralysis syndrome (West Nile poliomyelitis) is _____ (more or less) common than encephalitis or meningitis
who might you suspect has west nile virus
Consider WNV in any patient with unexplained encephalitis or meningitis
what does it mean if a person has IgM west nile + in serum but - in CSF
well we get lots of cross talk so a + serum can be a recent infection/vaccination against st louis or yellow fever

**CSF is only + if the infection is in the CSF- IgM cant cross BBB
what is the most important cause of mild encephalitis, what serotype are most cases caused by
california encephalitic, most common by LaCrosse serogroup
who is affected by california encephalitis

school ages boys

**commonly caused by LaCrosse serogroup
**important cause of mild encephalitis- daytme mosquite feedings
what is the reservoir for california encephalitis
small mammels

**mosquitoes are the vector as with ALL arbo virus. there is daytime mosquito feedings
what arbo is common in NW US
CO tock fever

reovirus, with 12 segments of ds RNA
what arbo has a sadlebacked fever pattern (up and down)
colorado tick fever

**most individuals have a history of tick sttachment or exposire

March- Oct in mountinous regions of NW US
what arbo virus has restrictions on blood donations
colorado tick fever, dont donate for like 6 months after infection (virus seeds progenitor cells)

**recall its a reovirus with 12 segemnts of dsRNA, common in NW US