Topic 62 - Equine influenza (WHITE)

Question 1

Definition of equine influenza

Answer 1

An acute, highly contagious disease causing fever and respiratory signs

Question 2

Occurrence of equine influenza

Answer 2

Worldwide, but NOT in New Zealand and Iceland

Question 3

Causative agent of equine influenza

Answer 3

Otrhomyxovirus, Influenzavirus A

Question 4

Influenza serotype causing equine influenza

Answer 4

H3N8
H7N7 is extinct

Question 5

Which proteins are the serotypes of influensa made up of?

Answer 5

NA = Neuraminidase
HA = haemagglutinin

Question 6

What is the function of HA?

Answer 6

It is the virus surface protein, the antireceptor.

The virus binds to the surface of the cell where we find siliac acid protein which is the receptor.

Question 7

What is the function of NA?

Answer 7

Its an enzyme.
It is responsible for the release of the virus from the cell.
the enzyme cuts the connection between virus particles and the cell membrane

Question 8

How does the NA and HA determine serotypes of the influenza, how is it done?

Answer 8

They are hypervariable genes, meaning that most of the mutations happens at the HA and NA genes.
There are serial point mutations, causing a antigenic drift which will make the seasonal influensas

Question 9

How many types does the NA and HA have, that can cause influensa types?

Answer 9

18 HA types
11 NA types

They combine freely.
The combinations are due to the segmented genome and if two different influensa viruses meet in the same cell, we get a segment re-assortment

Question 10

Explain how a re-assortment of segments work

Answer 10

1. 2 different influensa viruses meets in the cell
2. They replicate, making copies of the genome segments and at the end, the virus assemble happens ⭢ The segments get into the capsid mixed up
3. At the end of the virus replication, we have one original type virus. But due to the virus re-assortments, we also have two new types.
4. The host already have antibodies working for the original type, but they body do not recognise the new viruses and we get severe clinical signs ⭢ This is what we call the antigenic shift

Question 11

Route of infection in case of equine influneza

Answer 11

Airborne
Oral infections, by contaminated drinking water
Also by nose-to-nose contact

Question 12

How is equine influneza virus shed?

Answer 12

Shed through excretes, especially respiratory fluids ⭢ nasal discharge

Question 13

Is equine influneza contagious?

Answer 13

Very, only need 1 meter contact

Question 14

Pathogenesis of equine influneza

Answer 14

1. Infection of respiratory mucosa
2. Replication in epithelial cells of mucus membranes
3. There is a tracheal and bronchial mucosa damage, which induce inflammation.
4. Due to the virus replication we see nasal discharge at the beginning, after some time we have a Viremia
5. There is a strong interferon response and we see general signs such as: Fever, depression, muscle pain

Question 15

Days of incubation for equine influneza

Answer 15

1-3 days

Question 16

Clinical signs in case of equine influneza

Answer 16

High fever
Serous nasal discharge
Dry, unproductive cough
Depression
Weakness

With bacterial complications
Purulent nasal discharge
Pneumonia

Question 17

Can they recover from equine influneza?

Answer 17

Without complications they recover within few days and a complete recover is expected within 2-3 days

In comlicated cases:
Coughing for months
Permanent damages to the lungs
Death ⭢ mostly in donkeys

Question 18

Post mortem lesions in equine influneza

Answer 18

1. Inflammation in the respiratory tract
2. Oedema
3. Pneumonia signs
4. Histology: Necrosis of the cells and secondary bacterial superinfection causes lesions in the respiratory tract

Question 19

How to diagnose equine influneza

Answer 19

We do nasal swab!
RT-PCR is nr1 choice !!
Can do virus isolation, but it takes too long
We do Serology to identify if the animal is previously vaccinated or have been infected

Question 20

Differential diagnosis of equine influneza

Answer 20

Herpesvirus
Bacteria: Glanders

Question 21

Treament for equine influneza

Answer 21

Rest in dust-free environment
Give good quality feed and clean water
⭢ let the immune system work

Question 22

Control and prevention measures for equine influneza

Answer 22

1. New herds are quarantined
2. Immunisation - Vaccine
   If outbreak = Movement restrictions

Question 23

Type of vaccines use for equine influneza

Answer 23

Attenuated ⭢ Sprayed into the nasal cavity, inducing a IgA-type of local immunity
Inactivated

Question 24

When should foals, mares and racehorses be vaccinated against equine influenza?

Answer 24

Foals = from 6 months of age, then every year

Mares = 4-6 weeks before parturition

Race horses = Before racing season