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Flaviviridae Flashcards

(80 cards)

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1
Q

Faviviridae virion properties

A
  • spherical
  • 40-60 nm diameter
  • icosahedral symmetry
  • lipid envelope
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2
Q

What is the genome type of flaviviridae?

A

Single stranded, positive sense RNA

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3
Q

What gives the virus high susceptibility in the environment?

A

Envelope

- naked viruses are more hardy in the environment

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4
Q

Positive sense RNA

A

Single strand RNA which encodes mRNA and protein

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5
Q

What are the 3 genera of flaviviridae?

A
  • pestivirus (bovine viral diarrhea virus)
  • flavivirus (yellow fever virus)
  • hepacivirus (hepatitis C virus)
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6
Q

What are 4 species of pestivirus with animal health significance?

A
  • bovine viral diarrhea virus 1
  • bovine viral diarrhea virus 2
  • classic swine fever virus
  • border disease virus
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7
Q

Bovine viral diarrhea virus has ______ distribution

A

Worldwide

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8
Q

What are the 2 biotypes of viruses?

A
  • cytopathic

- noncytopathic

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9
Q

Which biotypes are virulent in cattle?

A

Both biotypes

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10
Q

Only _______ strains induce persistent infection

A

Non-cytopathic

- non-cytopathic can mutate to cytopathic

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11
Q

What clinical disease results from bovine viral diarrhea virus?

A

Mucosal

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12
Q

Why are cytopathic biotypes not persistent?

A

They destroy the cell (and their environment) upon infectivity

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13
Q

Transmission and persistence strategies of BVD

A
  • induction of persistently infected (PI) hosts that shed and transmit BVDV efficiently
  • suppression of host’s immune system
  • transmission by various direct and indirect routes
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14
Q

BVDV transmission

A
  • direct contact and aerosols
  • blood and secretions
  • meat products
  • mechanic vectors
  • in utero infection!
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15
Q

What is the main determinant of fetal response?

A

TIming of infection!

  • embryonic death: 0-50 days after conception
  • fetal abortion/mummification: 50-100 days
  • congenital defects: 100-150 days
  • normal: 150-200 days
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16
Q

Immunocompetent

A

150-200 days after conception

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17
Q

Tolerance/persistent infection

A

Occurs when infection in utero between 80-125 days of pregnancy

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18
Q

Immune tolerance

A

Immune system is not responding because infection is too early for the immune system to recognize the foreign antigen

  • aka: state of unresponsiveness for an antigen
  • lymphocytes will not respond to an antigen if they meet that antigen early in fetal life
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19
Q

BVDV infection in susceptible immunocompetent nonpregnant cattle causes:

A
  • subclinical infection
  • bovine viral diarrhea
  • infection in neonatal calves
  • venereal infections
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20
Q

Subclinical infections causes _____ infections in adult cattle

A

70-90%

  • mild fever and leukopenia
  • development of neutralizing antibodies
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21
Q

Bovine viral diarrhea is produced by ______

A

Both biotypes

  • infect cattle 6 months - 2 years old
  • depression, ocular discharge, oral erosions, ulcerations
  • diarrhea with high morbidity and low to moderate mortality
  • lesions in coronary band and interdigital cleft
  • decrease in milk production
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22
Q

Infection in neonatal calves

A

Rarely seen in calves younger than 6 months

- severe enteritis, sometimes fatal

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23
Q

Venereal infections

A

Semen in infected bulls contains virus (transient)

- semen quality may decrease (motility and morphologic abnormalities)

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24
Q

Seronegative cows inseminated with infective semen

A

Fail to conceive until they develop an immune response

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25
Mucosal disease occurs with:
2 biotypes of BVDV present - persistent infection with non-cytopathogenic virus - clinical signs similar to BVD but more severe - fever anorexia, profuse watery diarrhea, nasal discharge, erosive or ulcerative stomatitis, dehydration emaciation and death
26
Mucosal disease superinfection occurs with:
Cytopathogenic virus
27
Lesions
Acute BVD: erosive/ulcerative lesions in mouth, esophagus, forestomachs, abomasum and intestine - discoloration of mucosal folds (hyperemia and hemorrhage) - necrosis of lymphoid tissue (Peyer patches)
28
In utero infection may induce _________
Hypoplasia cerebellar
29
What are the rule outs for BVDV?
- rinderpest - foot and mouth disease - vesicular stomatitis
30
Laboratory testing
- viral isolation - viral antigen detection - RT-PCR - ELISA - ear notches
31
What laboratory test detects most persistently infected animals?
RT-PCR off an ear notch
32
Classic swine fever transmission
Main route of infection is oronasal by direct or indirect contact with infected pigs - indirect via contaminated feed
33
Classic swine fever severity depends on:
- age of the animal | - virulence of the virus
34
Classic swine fever signs
- acute infection: fever, depression, anorexia, conjunctivitis - neurological signs: staggering gait paresis, lethargic, circling, tremors, convulsions
35
What are the 3 forms of classic swine fever?
- peracute: kills young swine with no clinical signs - subacute - chronic: always fatal
36
____ and ______ forms by strains of moderate virulence
Subacute and chronic
37
Classic swine fever is a ______ virus that can replicate in any cell type
Pantropic
38
Typical skin hemorrhages of classic swine fever
Ears, tail, abdomen and the inner side of the limbs | - appear from second or third weeks after infection until death
39
Classic swine fever pathogenesis
Most common route by ingestion - replication leads to hemorrhages and leucopenia - disseminated intravascular coagulation, thrombosis
40
Primary viral replication occurs in ______
Tonsils - goes systemically from here - collect a tonsil specimen to detect and diagnose CSF
41
Secondary replication occurs in _______
Endothelial cells, lymphoid organs, bone marrow
42
CSF virus causes severe leukopenia and ________
Immunosuppression - dysfunction of immune system - antibodies may be temporarily detected in serum, but they are not able to eliminate the virus from the host
43
Lesions in the 3 forms of CSF
- peracute: may be no gross changes - acute: generalized submucosal and subserosal petechial hemorrhages, congestion and infarction in spleen, liver, bone marrow, lungs - subacute + chronic: necrotic ulceration of mucosa and LI - chronic: exhaustion of lymphoid system, atrophy of thymus and germinal center
44
________ is also a lesion of CSF
Non suppurative encephalitis
45
Prenatal infections
Infection in early pregnancy may result in abortions and stillbirths, mummification and malformations - infections between 50-70 days of pregnancy can lead to birth of persistently viremic piglets - piglets shed large amounts of virus!!
46
Rule outs of CSF
- African swine fever - erysipelas - porcine reproductive and respiratory syndrome - post weaning multisystemic wasting syndrome - salmonella - pasteurella
47
Recommended actions if CSF is suspected
Report immediately upon diagnosis or suspicion!!
48
CSF samples for lab testing
Should be sent under secure conditions and to authorized labs to prevent spread of disease - blood or tissue samples from acute cases for virus isolation, antigen detection or nucleic acid detection - tonsils, maxillary, submandibular and mesenteric lymph nodes, spleen, kidneys, distal part of ileum
49
Genus Flavivirus
Some viruses are arthropod-borne zoonotic pathogens - mosquito-borne encephalitides complex - tick borne virus complex
50
Arbovirus
Viruses transmitted to vertebrate hosts by blood sucking arthropod vectors
51
Flaviviruses with animal and human significance
- West Nile virus - japanese encephalitis virus - louping ill virus - zika virus
52
West Nile Virus is a member of the ______
Japanese encephalitis virus group
53
WNV is serologically related to ______
St Louis encephalitis and Japanese encephalitis virus
54
WNV
Endemic in Africa, Asia Southern Europe and North America | - transmission of virus among wild birds by infected mosquitoes
55
What are important reservoirs for WNV?
Passerines | - jay, finches, grackles, sparrows, crows
56
Principal mosquito vectors in the USA
- Culex pipiens | - Culex restvans
57
WNV has been isolated from over ______
300 species of birds
58
What are the 2 groups of WNV birds?
- asymptomatic: carriers - susceptible: crows, jays, magpies, house finches - --> develop neurological disease
59
WNV correlates with decline of ________
North American bird population
60
Since 1999, US has suffered a decrease of _______
Crow population
61
WNV avian infection
Range from subclinical to fatal with variability among species - neurological signs common
62
WNV lesions
- necrosis and enlargement of spleen and liver - myocardial degeneration - pancreatitis
63
WNV disease has been reported in _____ and _____
Ducks and geese (poultry)
64
_____, ______, and ______ are incompetent reservoirs
Psittaciformes, galliformes, columbiformes
65
What is an important factor in disease transmission of WNV?
Viremia | - minimal possibility of transmitting virus from bird to mosquito unless high viremia is present
66
In WNV, the mosquito becomes a ______
Biological vector, because it is also infected
67
Mammals are considered to be _______ carriers for WNV
Dead-end | - viremia and viral load in blood are not sufficient to transmit WNV back to the mosquito, ending the transmission cycle
68
What other animal species have been reported to show signs of WNV infection?
Horses | - also: goats, sheep, dog, wolf, alpaca, alligator, squirrels, crocodile, llama, cattle, seal, cat
69
Mammal infection with WNV
Most mammals are do not play a role in enzootic transmission - horses: depression, abnormal gait, ataxia, muscle tremors, recumbency - dogs and cats: no illness! - humans: neuroinvasive or non-neuroinvasive form (similar to flu)
70
West Nile Virus vaccine is available for ______
Horses
71
Rule outs for WNV in horses
- eastern equine encephalitis - venezuelan equine encephalitis - St. Louis equine encephalitis - equine herpesvirus - equine protozoal myeloencephalitis
72
WNV diagnosis
- RT-PCR | - IgM capure ELISA (acute infection)
73
Japanese encephalitis
Infects swine, horses, dogs, chickens, ducks, reptile, humans - important disease for travelers - fewer than 1 case/year in US citizens traveling to Asia
74
Japanese encephalitis symptoms
- horses: encephalitis - swine: subclinical with abortions stillbirth, and aspermia - humans: leading cause of encephalitis in Asia, diarrhea, headache, myalgia, paralysis, seizures, vomiting
75
Japanese encephalitis vector
Culex tritaeniorhynchus
76
Louping ill virus
Important in sheep - seen in Europe - neurological signs, hopping (louping) gait, nonsuppurative meningitis and encephalomyelitis
77
Louping ill virus vector
Tick borne - Ixodes ricinus - Rhipicephalus appendiculatus - humans infected via tick bites or by contact with the virus in tissues or lab cultures
78
Flavivirus in humans
- Yellow fever - St. Louis encephalitis - Dengue - Zika virus
79
Zika virus is a member of the ________
Spondweni virus group - primarily through the bite of an infected Aedes mosquito - illness is mild (symptoms last days to a week) - fever, rash, joint pain, conjuctivitis, muscle pain, headaches
80
Zika virus in Brazil
Reports of microcephaly and poor pregnancy outcomes in mothers who were infected with Zika virus while pregnant

Infectious Agents 2 (29 decks)

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