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(1) VMCB > (RNA VIRUSES) Lesson 15: Togaviridae > Flashcards

(RNA VIRUSES) Lesson 15: Togaviridae Flashcards

1
Q

General description of Togaviridae

A
  1. 60–70 nm in diameter
  2. Enveloped, RNA viruses with icosahedral symmetry
  3. Replicate in cell cytoplasm
  4. Labile in the environment
  5. Two genera, Alphavirus and Rubivirus
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2
Q

The family name Togaviridae e is taken from the Latin word ______.

A

toga

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3
Q

toga meaning

A

cloak or mantle

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4
Q

is a reference to the viral envelope of Togaviridae

A

cloak or mantle

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5
Q

Togaviridae: Enveloped or Non-enveloped

A

Enveloped

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6
Q

Togaviridae Replicate in

A

cytoplasm

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7
Q

Two genera of Togaviridae

A

Alphavirus and Rubivirus

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7
Q

in common with certain members of the Flaviviridae, Reoviridae, Rhabdoviridae and Bunyaviridae

A

Alphaviruses

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8
Q

Alphaviruses, in common with certain members of the Flaviviridae, Reoviridae, Rhabdoviridae and Bunyaviridae, are termed _________ indicating that they are arthropod- borne.

A

arboviruses

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9
Q

Alphaviruses / Genus Alphavirus cause what diseases

A

a. eastern equine encephalitis (EEE)
b. western equine encephalitis (WEE)
c. Venezuelan equine encephalitis (VEE)

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10
Q

major cause of zoonotic infections under Togaviridae

A

Alphaviruses / Genus Alphavirus

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11
Q

The majority of these viruses are found in tropical developing countries and have a
distinct geographical distribution.

A

arboviruses

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12
Q

The majority of arboviruses are found in ______ developing countries and have a
distinct geographical distribution.

A

tropical

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13
Q

Togaviridae
Ecological factors limiting the distribution of particular arboviruses include:

A

✓ temperature
✓ rainfall
✓ distribution of both vertebrate reservoir host and of the
arthropod vector

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14
Q

Togaviridae
The most important arthropod vectors.
The vector remains infected for life.

A

mosquitoes
midges
ticks
sandflies

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15
Q

Togaviruses of veterinary importance

A

1) Venezuelan
equine
encephalitis virus
(VEEV)
2) Eastern equine
encephalitis virus
(EEEV)
3) Western equine
encephalitis virus
4) Getah virus

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16
Q

Common arthropod vector of Togaviruses

A

Mosquito

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17
Q

Present in Central and South America with
occasional outbreaks in southern USA.

A

Venezuelan
equine
encephalitis virus
(VEEV)

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18
Q

Geographical distribution of Venezuelan
equine
encephalitis virus
(VEEV)

A

Central and South America w/
occasional outbreaks in southern USA

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19
Q

Venezuelan
equine
encephalitis virus
(VEEV) causes disease in

A

horses, donkeys and
man

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20
Q

Present in eastern USA, Caribbean and
South America

A

Eastern equine
encephalitis virus (EEEV)

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21
Q

Eastern equine
encephalitis virus
(EEEV) causes disease in

A

pheasants, horses and
man

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22
Q

Present throughout much of the Americas.

A

Western equine
encephalitis virus
(WEEV)

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23
Q

Western equine
encephalitis virus
(WEEV) causes disease in

A

horses and man

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24
Q

Milder disease than EEEV

A

Western equine
encephalitis virus
(WEEV)

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25
Q

Sporadic cause of disease in horses; fever,
urticaria and hind-limb oedema.

A

Getah virus

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26
Q

Getah virus: Sporadic cause of disease in these animals; fever,
urticaria and hind-limb oedema.

A

horses

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27
Q

Infection common in pigs but significance
unclear.

A

Getah virus

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28
Q

Present in Australia and southeast Asia

A

Getah virus

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29
Q

are important causes of nervous disease in horses in the New World which produce similar clinical signs

A

✓ Venezuelan equine encephalitis viruses (VEEV)
✓ Eastern equine encephalitis viruses (EEEV)
✓ Western equine encephalitis viruses (WEEV)

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30
Q

Several epidemiological features are common to the three diseases.

A

✓ Venezuelan equine encephalitis viruses (VEEV)
✓ Eastern equine encephalitis viruses (EEEV)
✓ Western equine encephalitis viruses (WEEV)

31
Q

Togaviruses: The peak of disease incidence coincides with the time of maximum vector numbers in late
summer or following the rains

A
32
Q

The Venezuelan equine encephalitis (VEE) complex comprises several viral species, divided into six subtypes I to VI

ENUMERATE

A

1) Subtype 1: have 5 serotypes (AB -F)

2) Subtype II : Everglades virus

3) Subtype III: Mucambo virus

4) Subtype IV: Pixuna virus

5-6) The viruses are maintained in sylvatic cycles involving rodents such as spiny rats (Proechimys chrysaeolus) and mosquitoes of the Culex (Melanoconion) and Aedes (Ochlerotatus) taeniorhynchus subgenus

33
Q

Subtype 1 of Venezuelan equine encephalitis (VEE) complex

A

have 5 serotypes (AB - F)

34
Q

Subtype II of Venezuelan equine encephalitis (VEE) complex

A

Everglades virus

35
Q

Subtype III of Venezuelan equine encephalitis (VEE) complex

A

Mucambo virus

36
Q

Subtype IV of Venezuelan equine encephalitis (VEE) complex

A

Pixuna virus

37
Q

The viruses (Everglades virus, Mucambo virus, Pixuna virus) are maintained in what cycles?

A

sylvatic cycles

38
Q

The viruses (Everglades virus, Mucambo virus, Pixuna virus) are maintained involving rodents such as spiny rats (Proechimys chrysaeolus) and mosquitoes of the Culex (Melanoconion) and Aedes (Ochlerotatus) taeniorhynchus subgenus

A

sylvatic cycles

39
Q

The viruses are maintained in sylvatic cycles involving the two organisms

A

✓ rodents such
as spiny rats
✓ mosquitoes

40
Q

SN of spiny rats

A

Proechimys chrysaeolus

41
Q

SN of Culex

A

Melanoconion

42
Q

SN and subgeus of Aedes

A

✓ Ochlerotatus
✓ taeniorhynchus

43
Q

is found principally in Atlantic
coastal areas of the USA, Canada, Michigan, the Caribbean Basin and South
America.

A

Eastern equine encephalitis virus (EEEV)

44
Q

Two distinct lineages of EEEV

A

✓ North American (pathogenic group I)
✓ South American (Groups IIA, IIB and III)

45
Q

Lineage of EEEV pathogenic group I

A

North American

46
Q

Lineage of EEEV under Groups IIA, IIB and III

A

South American

47
Q

The virus is maintained in cycles of infection involving passerine
birds and the irrigation ditch mosquito Culiseta melanura

A

Eastern equine encephalitis virus (EEEV)

48
Q

SN of irrigation ditch mosquito

A

Culiseta melanura

49
Q

Western equine encephalitis virus (WEEV) cycle of infection involves
_______

A

✓ mosquitoes, mainly Culex tarsalis
✓ wild birds

50
Q

cycle of infection involves
mosquitoes, mainly Culex tarsalis, and wild birds

A

Western equine encephalitis virus (WEEV)

51
Q

Western equine encephalitis virus (WEEV) cycle of infection involves
mosquitoes, mainly __________, and wild birds.

A

Culex tarsalis

52
Q

these animals are infected by WEEV incidentally and are dead-end hosts, developing
only low titres of virus in the blood.

A

Horses

53
Q

A related virus of WEEV, occurs in the eastern United
States and causes encephalitis in horses rarely.

A

Highlands J virus

54
Q

A related virus of WEEV, Highlands J virus, causes what?

A

encephalitis in horses rarely

55
Q

A related virus of WEEV, Highlands J virus, causes encephalitis rarely in what animals?

A

horses

56
Q

incubation period of Togaviruses

A

1-9 days

57
Q

clinical
signs of Togaviruses usually last for how many days?

A

4-9 days

58
Q

Replication of Togaviruses occurs where

A

✓ near the site of inoculation by a feeding mosquito
✓ local draining lymph nodes

59
Q

TOGAVIRUSES

Viraemia ranging from barely detectable to an exceedingly high titre
follows. This is accompanied by fever.

A
60
Q

In severe cases the Togavirus invades the _______
resulting in neuronal necrosis, perivascular cuffing and interstitial mononuclear inflammatory infiltration.

A

central nervous system

61
Q

In severe cases the Togaviruses invades the central nervous system
resulting in

A

✓ neuronal necrosis
✓ perivascular cuffing
✓ interstitial
mononuclear inflammatory infiltration (IMII)

62
Q

Clinically, the diseases caused by the three togaviruses are very similar

A
63
Q

The 3 togaviruses vary in severity from mild signs of fever and depression to a
fatal febrile encephalomyelitis.

A
64
Q

The case fatality rate is highest for EEE at ____%.

A

90%

65
Q

case fatality rate is ___% for
VEE

A

50–80%

66
Q

case fatality rate is ___% for WEE

A

20–40%

67
Q

The case fatality rate is highest for this togavirus at 90%

A

EEE

68
Q

Recovered horses (affected by togaviruses) are usually normal but a few may have residual
nervous signs.

A
69
Q

Laboratory work with these viruses (VEEV, EEEV, WEEV) should only be carried out by
________ in ________ following containment level ____
procedures.

A

immunized personnel
biosafety cabinets
level 3

70
Q

definitive diagnostic technique if togaviruses is

A

virus isolation (lab animal inoculation, embryo inoculation, cell culture)

71
Q

TOGAVIRUSES

Specimens to be collected:

A

✓ whole blood
✓ brain
tissue
✓ cerebrospinal fluid (CSF)

72
Q

TOGAVIRUSES

Specimens to be collected: whole blood during what stage?

A

pyrexic stage

73
Q

TOGAVIRUSES

Specimens to be collected for horses which died following
nervous disease

A

brain
tissue or CSF

74
Q

Diagnosis of Togaviruses

A

✓ RT-PCR
✓ Serology
• ELISA
• plaque reduction neutralization assay
• complement
fixation
• haemagglutination inhibition

(1) VMCB (13 decks)

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