Flaviviridae

Question 1

Who were the first doctors to recognize Yellow Fever (a flavivirus) as a filterable agent?

Answer 1

Walter Reed and James Carroll

Question 2

What are the 3 genera of Flaviviridae

Answer 2

Flavivirus
Pestivirus
Hepacivirus

Question 3

What glycoproteins can be found on the envelope of flaviriuses?

Answer 3

E1 or E2

Question 4

Flaviviruses are ________ stranded, _______ sense RNA

Answer 4

Single stranded

positive sense

Question 5

T/F: Flavivirus RNA is infectious

Answer 5

TRUE

Question 6

Where in the cell does replication occur?

Answer 6

Cytoplasm

Question 7

Where are viral proteins transported to after synthesis?

Answer 7

Endoplasmic reticulum

This differs from other viruses that immediately send viral proteins out of the cell

Question 8

T/F: Release of flaviviruses from host cells causes cell lysis

Answer 8

FALSE (differs from other viruses)

this is why many times these viruses may be asymptomatic

Question 9

T/F: Heat, disinfectants, and lipid solvents inactivate flavivirueses

Answer 9

TRUE

***classical swine fever virus is the only exception - may withstand the heat of cooking

Question 10

Who are dead end hosts of West Nile Virus?

Answer 10

Horses and humans

Question 11

In who is the West Nile Virus maintained?

Answer 11

Mosquitoes and Birds

Question 12

T/F: Horses have high viremia when infected with WNV

Answer 12

FALSE

this is why they are a dead end host

Question 13

What are clinical signs in birds with WNV?

Answer 13

High viremia, widespread necrosis and hemorrhage of organs –> DEATH

Question 14

What is the prognosis for a horse with WNV showing neurological signs (ataxia, recumbence)?

Answer 14

POOR

Question 15

What clinical signs may you see in a horse with WNV?

Answer 15

HIGH FEVER, decreased appetite, depression, weakness, neuro signs

Question 16

When should samples be collected for dx testing of WNV in a horse and what sample will you collect?

Answer 16

Blood collection should happen within 5 days of clinical presentation of west nile virus

Question 17

What is the preferred dx test for WNV?

Answer 17

ELISA - looking for IgM

other - virus neutralization, RT-PCR, immunohistochemistry, virus isolation

Question 18

T/F: Horses who recover from WNV will have good immunity and not require the vaccine in the future

Answer 18

TRUE

Question 19

What genus does BVDV (Bovine viral diarrhea virus) belong to?

Answer 19

Pestivirus

Question 20

T/F: BVDV can infection sheep, goats, and swine

Answer 20

True

Cattle are the most important host affected by this virus

Question 21

What makes an outbreak of BVDV in a naïve herd different than a herd that has had previous exposure?

Answer 21

Higher morbidity and mortality in naïve herds

Easier to dx in naïve herds

Question 22

What are the MOT of BVDV?

Answer 22

Vertical -> embryo/fetus
Food contamination and artificial insemination

(virus is shed in nearly all secretions and excretions)

Question 23

What clinical signs do you see in a non-pregnant cow with BVDV?

Answer 23

*most common in young cows
Decreased milk production, biphasic fever, DHR,
**Nasal discharge and ulcerations on lips, muzzle, oral cavity

Question 24

What clinical signs do you see in a pregnant cow with BVDV?

Answer 24

Early pregnancy: embryonic death and resorption

Before immunological competence of fetus: “weak calf syndrome”, Birth deformities and retarded growth post birth, calves that survive will be SERONEGATIVE carriers

Late: may have immune response and eliminate virus

Question 25

What is the mechanism that occurs to a calf in utero that allows it to be born as a seronegative carrier of BVDV?

Answer 25

immunotolerance

Question 26

What is the mortality rate in calves with persistent BVDV infection?

Answer 26

50%

Question 27

What are 2 disease syndromes of BVDV?

Answer 27

Bovine viral diarrhea
Mucosal disease (comes after BVD - chronic)

Question 28

What are 2 BVDV types?

Answer 28

Cytopathic and non-cytopathic (usually persistent)

Question 29

What clinical signs will you notice in a cow with chronic mucosal disease due to BVDV?

Answer 29

*Skin ulcers and hyperkeratosis on head/neck/shoulders

will note necrosis at the crypts of enterocytes at necropsy

Question 30

What dx test(s) should be performed to dx BVDV?

Answer 30

Virus isolation
Immunohistochemistry with ear notch sample
Then confirm with RT-PCR

Question 31

What must be done before vaccinating a herd of cattle for BVDV?

Answer 31

Must perform screening and eliminate any carriers

Inactivated/attenuated and modified live vax available

Question 32

T/F: Classical swine fever is a reportable disease

Answer 32

TRUE!!!!

Question 33

T/F: Classical swine fever outbreaks occur periodically in the US

Answer 33

FALSE
Classical swine fever has been eradicated in:
North America, Australia, NZ, Ireland, UK

Question 34

What is the MOT of classical swine fever?

Answer 34

Oronasal route - direct contact/fomites

May be present in contaminated pork products

Question 35

What dz type is most common form of classical swine fever and what clinical signs will you see? (ex: peracture, acute, chronic)

Answer 35

ACUTE (mortality can reach 100%)

high fever, **hyperemia from ear tips –> progresses all over body (redness), anorexia, depression, DHR/vomiting, conjunctivitis, CNS signs

Question 36

What samples and tests should be collected/performed to dx classical swine fever?

Answer 36

Tissue samples should be collected and sent to a REFERENCE LAB for ELISA or RT-PCR

Question 37

How do you treat classical swine fever?

Answer 37

CULL

Question 38

T/F: There is no vaccine available for classical swine fever

Answer 38

FALSE

attenuated and live vaccines are available

Question 39

T/F: ticks can transmit west nile virus

Answer 39

TRUE