Exam 2: Flaviviridae

Question 1

What are the virion properties of Flaviviridae?

Answer 1

Virions are spherical
Diameter 40-60 nm (medium sized)
Inner core possible icosshedral symmetry
Lipid envelope
Genome: single stranded, positive sense RNA

Question 2

What are the 3 genera of flaviviridae?

Answer 2

Pestivirus (BVDV)
Flavivirus (yellow fever virus)
Hepacivirus (hepatitis C)

Question 3

What are the species of pestiviruses with animal health significance?

Answer 3

Bovine viral diarrhea virus 1
BVDV 2
Classic swine fever virus

Question 4

What are the 2 biotypes of virus with BVDV?

Answer 4

Cytopathic

Non-cytophatic

Question 5

Which biotype induces persistent infection with BVDV?

Answer 5

Non-cytophatic

Question 6

Which BVDV biotype is/are virulent in cattle?

Answer 6

Both cytopathic and non-cytopathic may be

Question 7

What are the transmission and persistence strategies of BVD?

Answer 7

Induction of persistently infected hosts that shed and transmit BVDV efficiently
Suppression of the host’s immune system
Transmission by various direct and indirect routes

Question 8

What is the most important method of transmission for BVDV?

Answer 8

In utero infection

Question 9

What is the main determinant of fetal response in transplacental infections?

Answer 9

Timing of infection during pregnancy

Question 10

Describe subclinical infections from BVDV in susceptible immunocompetent nonpregnant cattle

Answer 10

70 to 90% of infections in adult cattle
Mild fever and leukopenia
Development of neutralizing antibodies

Question 11

Describe BVDV infection in neonatal calves

Answer 11

Rarely seen in calves younger than 6 months

Severe enteritis, sometimes fatal

Question 12

Describe venereal infections from BVDV

Answer 12

Semen in infected bulls contains virus
Semen quality may decrease
Seronegative cows inseminated with infective semen fail to conceive until they develop an immune response

Question 13

What is immunological tolerance?

Answer 13

State of unresponsiveness for a particular antigen

Question 14

When does immunological tolerance occur with BVDV?

Answer 14

When infection in utero between 80 and 125 days of pregnancy

Question 15

Describe mucosal disease associated with BVDV

Answer 15

2 biotypes of BVDV are present
Persistent infection with non-cytopathogenic virus
Superinfection with a cytopathogenic virus
Clinical signs are similar to BVDV but more severe

Question 16

What are the lesions with BVD?

Answer 16

Acute: erosive or ulcerative lesions in mouth, esophagus, forestomachs, abomasum and intestine
Discoloration of mucosal folds
Necrosis of lymphoid tissue

Question 17

What is used to diagnose BVDV?

Answer 17

RT-PCR
ELISA
Ear notches

Question 18

What is the main route of classic swine fever infection?

Answer 18

Oronasasl by direct or indirect contact with infected pigs

Indirect by contaminated feed

Question 19

What does the severity of classic swine fever signs depend on?

Answer 19

Age of the animal and virulence of the virus

Question 20

Which form of classic swine fever is always fatal?

Answer 20

Chronic form

Question 21

What are the typical skin hemorrhages of classic swine fever?

Answer 21

Ears, tail, abdomen, and the inner side of the limbs

Question 22

Where does primary viral replication occur with classic swine fever?

Answer 22

Tonsils

Question 23

What does classic swine fever cause?

Answer 23

Severe leukopenia and immunosuppresion

Question 24

What is the major lesion caused by classic swine fever?

Answer 24

Infarction in the spleen

Question 25

Describe prenatal infections of classic swine fever

Answer 25

The piglets shed large amounts of virus

Question 26

What should be done classical swine fever is suspected?

Answer 26

It should be reported immediately

Question 27

Where should a sample come from when testing for classic swine fever?

Answer 27

Tonsils

Question 28

What can transmit Flavivirus?

Answer 28

Mosquito | Ticks

Question 29

What are viruses that fall in the Flavivirus genus?

Answer 29

West Nile Virus Japanese encephalitis virus Louping ill virus Zika virus

Question 30

What is West Nile Virus serologically related to?

Answer 30

St. Louis encephalitis

Question 31

What are important reservoirs of West Nile Virus?

Answer 31

Passerines

Question 32

What are the prinicpal vectors of West Nile Virus in the USA?

Answer 32

Culex pipiens | C. restvans

Question 33

What are the 2 groups of birds infected with West Nile Virus?

Answer 33

Asymptomatic (carriers) | Susceptible (develop neurological disease)

Question 34

What does West Nile VIrus correlate with in terms of the North American bird population?

Answer 34

The decline in the population

Question 35

What is the range of avian West Nile Virus infections?

Answer 35

Subclinical to fatal with variability among species

Question 36

What are the signs associated with West Nile Virus?

Answer 36

Neurological

Question 37

In poultry, what has West Nile Virus been mostly reported in?

Answer 37

Ducks and geese

Question 38

What is another major animal that West Nile Virus has been reported in?

Answer 38

Horses

Question 39

What must you rule out in horses before you can confirm West Nile Virus?

Answer 39

Eastern Equine Encephalitis

Question 40

What is Japanese encephalitis a concern for?

Answer 40

Travelers

Question 41

What is Louping ill virus important in?

Answer 41

Sheep

Question 42

What ticks transmit Louping ill virus?

Answer 42

Ixodes ricinus | Rhipicephalus appendiculatus

Question 43

What are the signs associated with Louping ill virus?

Answer 43

Neurological

Question 44

What are the flaviviruses in humans?

Answer 44

Yellow fever St. Louis encephalitis Denge Zika virus

Question 45

How is Zika virus transmitted?

Answer 45

Primarily though the bite of an infected Aedes species mosquito