Equine Influenza Virus


Caused by equine influenza virus. It affects horses, donkeys, mules and zebras and although rarely fatal deaths have been reported in horses and especially donkeys.


1) Non-vaccinated animals
High temperature within 1-3 days of infection may last for 7-10 days.
Harsh dry cough develops which persists for 2-3 weeks.
Horses are depressed and off feed.
Watery nasal discharge which may become thick pus discharge with time.
Normally there is a rapid spread of disease within an unvaccinated group.

2) Vaccinated Horses
Clinical signs become modified and difficult to distinguish from other respiratory viruses.
Mild short lived temperature.
Occasional cough and watery nasal discharge may be the only signs.
Laboratory tests are required to confirm the diagnosis.


Requires naso-pharyngeal (nasal swabs) for laboratory analysis. Blood samples taken during the early (acute) and late (convalescent) stage of the disease can provide retrospective diagnosis.


1) Rapid diagnosis and restriction of movement.


Most equestrian bodies advise following the vaccination protocol laid down by the Horseracing Regulatory Authority:

Primary vaccination course of 3
1st Vaccination
2nd Vaccination after 21 - 92 days
3rd Vaccination after 150 - 215 days
Booster vaccinations
Then annual boosters within 365 days

N.B. - The FEI require an influenza vaccination within 6 months of the last vaccination.


No direct treatment.
Rest and bandaging if temperature is high.
1 week off for every day of significant temperature over (102.5).

If a secondary bacterial infection develops antibiotic therapy may be required.

Scott Dunn’s Equine Clinic is part of CVS (UK) Limited, a company which owns over 300 veterinary practices in the UK. Company Registration Number 03777473. Registered Office CVS House, Owen Road, Diss, Norfolk, IP22 4ER