Topic 62 - Equine influenza (WHITE) Flashcards
Definition of equine influenza
An acute, highly contagious disease causing fever and respiratory signs
Occurrence of equine influenza
Worldwide, but NOT in New Zealand and Iceland
Causative agent of equine influenza
Otrhomyxovirus, Influenzavirus A
Influenza serotype causing equine influenza
H3N8
H7N7 is extinct
Which proteins are the serotypes of influensa made up of?
NA = Neuraminidase
HA = haemagglutinin
What is the function of HA?
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.
What is the function of NA?
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
How does the NA and HA determine serotypes of the influenza, how is it done?
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
How many types does the NA and HA have, that can cause influensa types?
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
Explain how a re-assortment of segments work
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
Route of infection in case of equine influneza
Airborne
Oral infections, by contaminated drinking water
Also by nose-to-nose contact
How is equine influneza virus shed?
Shed through excretes, especially respiratory fluids ⭢ nasal discharge
Is equine influneza contagious?
Very, only need 1 meter contact
Pathogenesis of equine influneza
- Infection of respiratory mucosa
- Replication in epithelial cells of mucus membranes
- There is a tracheal and bronchial mucosa damage, which induce inflammation.
- Due to the virus replication we see nasal discharge at the beginning, after some time we have a Viremia
- There is a strong interferon response and we see general signs such as: Fever, depression, muscle pain
Days of incubation for equine influneza
1-3 days
