Flashcards in togaviridae Deck (22):
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togaviridae classification
genus-alphavirus (arthropod borne)
genus-rubivirus (rubella)
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togaviridae morphology
linear single stranded + sense
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Alphaviruses
Western equine encephalitis (WEEV)
eastern equine encephalitis (EEEV)
venezuelan equine encephalitis (VEEV)
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EEEV distribution
zoonotic by mosquitos in easter NA carribbean and central america, encephalitis in horses and humans, 4 lineages, 1 is in NA, other (II, III, IV) are less virulent
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EEEV transmission
epizootic involves birds and mosquitos that transmit to pheasants or dead end hosts
enzootic transfers to marsh birds or reptiles/rodents
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Path EEEV
mosquito bite-enters CNS through hematgenous route, replication in neurons and glial cells, apoptosis, non suppurative encephalomyelitis
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EEEV in horses
fever, anorexia, depression, hypersensative to sound, colic, walk blindly, can't hold up head, leaning back, cannot hold up head
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EEEV in humans
most cases no apparent illness,
systemic form-arthralgia, myalgia, no CNS
Enceph form-anorexia, vomiting diarrhea cyanosis, convulsions
prognosis- 30% die, recovered may have permanent brain damage
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EEEV in birds
asymptomatic, tremors, leg paralysis, involuntary circular movements
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WEEV
may have emerged from EEEV genetic recombination, found in NA and SA, NA strains more virulent, WEEV lower fatality and less virulent than EEEV
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WEEV cycles of transmission
enzootic (Culex)-house sparrow or house finch amplifying hosts
epizootic vector (Aedes)- rodents including prairie dogs and rabbits
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WEEV horses clinical signs
mild or asymtomatic mostly, otherwise show symptoms of EEEV
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WEEV humans clinical signs
mild or asymptomatic, infants are highly susceptible
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Venezuelan Equine Encephalitis virus
(VEEV)
epizootic (highly virulent for equines)-I-A, I-B, I-C subtypes
enzootic-not virulent for horses I-D, I-E, I-F subtypes
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VEEV enzootic cycle
Culex primary vector with rats and Aedes; horses and humans accidental hosts
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VEEV epizootic cycle
mosquito to horses, accidental host humans (dead end)
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mutation of endemic strains
can become epidemic strains, 1AB virus may arise from mutation of endemic strains (1D-F)
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clinical signs VEEV
non-suppurrative enchephalomyelitis, in-utero infection may occur, same signs as EEEV (leaning stance, lack of coordination, dead horse)
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humans clinical signs VEEV
normally acute, mild, systemic disease, encephalitis symptoms
*may cause placental damage in pregnant women, or fetal encephalitis, or abortion/stillbirth, or congenital disease
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control of all forms EEV
mosquito control-repair leaky faucets, cover rain barrels, change stagnate water sources,, etc.
can use mosquito traps, report dead birds, use chicken serology testing, use natural enemies, incesticides
wear protective clothing, insect repellants, nets
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vaccination in horses
formalin inactivated for WEEV and EEEV univalent or bivalent with tetanus toxoid
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