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Flashcards in togaviridae Deck (22):
1

togaviridae classification

genus-alphavirus (arthropod borne)
genus-rubivirus (rubella)

2

togaviridae morphology

linear single stranded + sense

3

Alphaviruses

Western equine encephalitis (WEEV)
eastern equine encephalitis (EEEV)
venezuelan equine encephalitis (VEEV)

4

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

5

EEEV transmission

epizootic involves birds and mosquitos that transmit to pheasants or dead end hosts
enzootic transfers to marsh birds or reptiles/rodents

6

Path EEEV

mosquito bite-enters CNS through hematgenous route, replication in neurons and glial cells, apoptosis, non suppurative encephalomyelitis

7

EEEV in horses

fever, anorexia, depression, hypersensative to sound, colic, walk blindly, can't hold up head, leaning back, cannot hold up head

8

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

9

EEEV in birds

asymptomatic, tremors, leg paralysis, involuntary circular movements

10

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

11

WEEV cycles of transmission

enzootic (Culex)-house sparrow or house finch amplifying hosts
epizootic vector (Aedes)- rodents including prairie dogs and rabbits

12

WEEV horses clinical signs

mild or asymtomatic mostly, otherwise show symptoms of EEEV

13

WEEV humans clinical signs

mild or asymptomatic, infants are highly susceptible

14

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

15

VEEV enzootic cycle

Culex primary vector with rats and Aedes; horses and humans accidental hosts

16

VEEV epizootic cycle

mosquito to horses, accidental host humans (dead end)

17

mutation of endemic strains

can become epidemic strains, 1AB virus may arise from mutation of endemic strains (1D-F)

18

clinical signs VEEV

non-suppurrative enchephalomyelitis, in-utero infection may occur, same signs as EEEV (leaning stance, lack of coordination, dead horse)

19

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

20

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

21

vaccination in horses

formalin inactivated for WEEV and EEEV univalent or bivalent with tetanus toxoid

22

vaccination in humans

no vaccine