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Infectious Agents 2 > Togaviridae > Flashcards

Togaviridae Flashcards

1
Q

Which 3 viruses belong to the family alphavirus that are of veterinary importance?

A
  • eastern equine encephalitis virus
  • western equine encephalitis virus
  • venezuelan dquine encephalitis virus
  • are all part of group A**
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2
Q

Most alphaviruses are _______

A

Neurotropic

  • distributed worldwide
  • maintained in enzootic infection cycle
  • specific mosquito and vertebrate host
  • host range defined by feeding preference of insect host
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3
Q

Animals and humans are ______ hosts

A

Dead end

- may serve as amplifying hosts

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4
Q

What are the 3 categories of alphaviruses?

A
  • neurological disease (encephalitis)
  • febrile illness with polyarthritis
  • no apparent disease
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5
Q

Western equine encephalitis virus includes:

A
  • western equine encephalitis virus

- highlands J virus

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6
Q

Getah virus is located in _____

A

Southeast Asia

- febrile disease

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7
Q

Semiliki forest virus is located in ______

A

Africa

- febrile disease

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8
Q

Togaviridae morphology

A

Spherical virions

- lipid envelope with fine spikes

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9
Q

Togaviridae genome

A

Single stranded, positive sense RNA (same as mRNA)

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10
Q

What 4 viruses encompass equine alphaviruses?

A
  • eastern equine encephalitis virus
  • western equine encephalitis virus
  • venezuelan equine encephalitis virus
  • highlands j virus
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11
Q

Equine alphaviruses cause sever disease in _______

A

Horses and humans

  • birds or mammals serves as reservoirs
  • progressive systemic disease and death (fever, drowsiness, incoordination, depression, neurologic manifiestations
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12
Q

Neurological manifestations of equine alphaviruses

A
  • abnormally wide stance
  • hanging head, drooping ears, flaccid lips
  • irregular gait
  • signs of encephalitis (impaired vision, photophobia, inability to swallow)
  • head pressing
  • inability to rise, paralysis, convulsions
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13
Q

Case mortality rate

A
  • EEEV (lineage 1): 50-90%
  • WEEV: 40%
  • VEEV: 80%
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14
Q

EEEV is enzootic in _______

A

Eastern US, Caribbean basin, Central America

  • maintained in North America in resident birds in freshwater marshes
  • viremic in wading birds, passerine and starlings
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15
Q

Vector of EEEV

A
  • ornithophilic mosquito: Culiseta melanura

- bride mosquitoes: Aedes and Coquillettidia

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16
Q

EEEV is amplified in ______

A

Spring and summer

- oubreaks occur in late summer, fall

17
Q

EEEV susceptible species

A

Virutally all birds are susceptible

  • passerine develop high titer viremia, minimal mortalitiy
  • clinical disease occurs in pheasants, partridges, and turkeys
18
Q

WEEV

A

North American strains are more prevalent

- passerine birds and Culex tarsalis

19
Q

Feeding pattern of Culex tarsalis

A
  • spring: birds

- late summer: mammals

20
Q

WEEV susceptible species

A

Rodents, rabbits, bats, squirrels, ungulates, tortoises, emus

21
Q

What are the 2 subgroups of venezuelan equine encephalitis virus?

A
  • enzootic VEE: groups 1-6

- epizootic VEE: group 1, subtype 1AB, and 1C

22
Q

Enzootic VEEV

A

Groups 1-6 in Central/South America, group 3 in Florida

  • Culex spp (melanoconion) and small animals (cotton, spiny rats)
  • horses do not develop enough viremia to infect mosquitoes
  • rarely clinical in humans and domestic animals
23
Q

Epizootic VEEV

A

Venezuela, Colombia, Peru, and Ecuador

  • virulent to horses with high viremia
  • horses serve as amplification host
  • severe disease in horses, neurological sequelae
24
Q

Highland J virus

A

Sporadic cause of encephalitis in horses

- pathogenic for turkeys and partridges

25
Q

Prevention and control

A

Reduce mosquito exposure and vaccinate

26
Q

Vaccination for equine alphaviruses

A

Immunity is lifelong!

  • inactivated vaccines for EEE, WEE, and VEE
  • annual after 2-3 primary immunizations
  • used in emus and endangered avian species
27
Q

Is the genome of togaviridae infectious?

A

Yes!

  • positive sense RNA molecule that can directly translate viral proteins for replication or by transfection of susceptible cells
  • naked viral RNA molecule that can produce infectious viral particles
28
Q

What are the amplifying hosts for VEEV?

A

Wild birds, equine, and other mammals!!

29
Q

Geographic distributions of alphaviruses

A
  • EEEV: fresh water swamp

- WEEV: irrigation areas and rural areas

30
Q

Neurological disease is most severe in _______

A

EEE

31
Q

Transmission cycle

A

Virus enters blood via saliva of infected female mosquito –> targets monocytes and endothelial cells near the entry site or in regional lymph node –> replication results in primary viremia which allows virus to invade extraneural tissues –> further replication leads to secondary viremia

32
Q

What is necessary for the virus to invade the CNS?

A

Higher titers of virus in the blood

- infect the capillary endothelial cells to enter the CNS = neuronal necrosis

33
Q

What are the most severely infected areas of brain in terminal cases of alphavirus infection?

A
  • cerebral cortex
  • thalamus
  • hypothalamus
34
Q

Diagnosis of active infection

A

IgM captured ELISA

- last several weeks after infection

Infectious Agents 2 (29 decks)

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