Flavivirus- West Nile

Question 1

What is an arbovirus?

Answer 1

An Arthropod-Borne Virus

Question 2

What kind of virus is a flavivirus?

Answer 2

Positive Sense, Single-Stranded

Question 3

How many polyproteins is a flavivirus?

Answer 3

One- cleaved by viral and host proteases
- releases mature polypeptide products v

Question 4

What does the outside of the flavivirus look like?

Answer 4

Icosahedral capsid
* Envelope inactivated by detergents, high temps etc.

Question 5

What are the 5 steps of flavivirus pathogenicity?

Answer 5

1. Mosquito bite (virus is injected into the skin and micro blood vessels)
2. Virus enters both the keratinocytes and APC’s
3. innate immune response
4. Enters local lymph nodes then goes on to enter the bloodstream
5. Crosses the BBB to enter the brain
6. another immune response- high levels of inflammation can be detected using histopathology

Question 6

What are the clinical signs of WNV in horses?

Answer 6

• The incubation period is around 9-11 days
• Pyrexia
• Nervous signs
• Depression
• Ataxia
• Flaccid lower lip
• Paralysis/ Suddem death

Question 7

What are the diagnostic tests for WNV?

Answer 7

• Serology/ Blood (ELISA’s, Plaque reduction neutralisation test)
• Molecular diagnosis (looking for the virus)
• RT-PCR
• Tissue samples
• Pen-flavivirus PCR
• Whole genome sequencing

Question 8

What does TBEV infect

Answer 8

• Wild rodents
• Large mammals such as sheep and goats
• humans are dead-end hosts

Question 9

Where is TBEV endemic?

Answer 9

• Northern china and japan

Question 10

What inactivates the flavivirus envelope?

Answer 10

It is inactivated by-
* Detergents and organic solvents
* Low and high pH, below 3 and above 10
* High temperature >70
* UV

Question 11

What animal species have high levels of WNV viraemia?

Answer 11

Birds and Mosquitos

Question 12

Name three differential diagnosis for WNV

Answer 12

• Eastern equine encephalomyelitis
• Venezualan equine encephalomyelitis
• Western equine encephalomyelitis

Question 13

What are the two serology tests you would do for WNV?

Answer 13

• ELISA’s (igM)
• Plaque Reduction Neutralisation test

Question 14

Name 4 important mosquito-borne flaviviruses with animal reservoirs

Answer 14

• St Louis Encephalitis
• Yellow Fever
• Dengue
• Japenese encephalitis

Question 15

Name three important points surrounding tick-borne flaviviruses

Answer 15

1. Similiar to mosquito-borne but with a different lifecycle
2. True vector-borne- virus replicates in the tick
3. High viraemia in host mammals
4. have wildlife reservoirs

Question 16

What helps maintain tick-borne encephalitis virus?

Answer 16

Maintained in a cycle involving hard ticks and wild vertebrate hosts

human vaccines are available

Question 17

What virus is highly related to TBEV?

Answer 17

louping ill virus

Question 18

What happens if a test result is WNV positive?

Answer 18

• Authorites will not cull horse or put in restrictions
• No compensation
• 30% mortality in clinically infected horses