togaviridae

Question 1

togaviridae classification

Answer 1

genus-alphavirus (arthropod borne)

genus-rubivirus (rubella)

Question 2

togaviridae morphology

Answer 2

linear single stranded + sense

Question 3

Alphaviruses

Answer 3

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

Question 4

EEEV distribution

Answer 4

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

Question 5

EEEV transmission

Answer 5

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

Question 6

Path EEEV

Answer 6

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

Question 7

EEEV in horses

Answer 7

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

Question 8

EEEV in humans

Answer 8

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

Question 9

EEEV in birds

Answer 9

asymptomatic, tremors, leg paralysis, involuntary circular movements

Question 10

WEEV

Answer 10

may have emerged from EEEV genetic recombination, found in NA and SA, NA strains more virulent, WEEV lower fatality and less virulent than EEEV

Question 11

WEEV cycles of transmission

Answer 11

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

Question 12

WEEV horses clinical signs

Answer 12

mild or asymtomatic mostly, otherwise show symptoms of EEEV

Question 13

WEEV humans clinical signs

Answer 13

mild or asymptomatic, infants are highly susceptible

Question 14

Venezuelan Equine Encephalitis virus

VEEV

Answer 14

epizootic (highly virulent for equines)-I-A, I-B, I-C subtypes
enzootic-not virulent for horses I-D, I-E, I-F subtypes

Question 15

VEEV enzootic cycle

Answer 15

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

Question 16

VEEV epizootic cycle

Answer 16

mosquito to horses, accidental host humans (dead end)

Question 17

mutation of endemic strains

Answer 17

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

Question 18

clinical signs VEEV

Answer 18

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

Question 19

humans clinical signs VEEV

Answer 19

normally acute, mild, systemic disease, encephalitis symptoms
*may cause placental damage in pregnant women, or fetal encephalitis, or abortion/stillbirth, or congenital disease

Question 20

control of all forms EEV

Answer 20

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

Question 21

vaccination in horses

Answer 21

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

Question 22

vaccination in humans

Answer 22

no vaccine