A highly contagious, viral disease of the respiratory system caused by different strains of influenza virus. A horse contracts the virus either by contact with an infected horse or indirectly by contaminated air/environment. Infected horses incubate the virus for only 1-3 days before developing symptoms, which is why outbreaks of influenza spread so rapidly.


• An increased temperature up to 41 degrees C (106 degrees F) for 1-3 days
• A harsh dry cough of sudden onset that persists for 2-3 weeks or more
• Clear nasal discharge progressing to thick yellow discharge
• Lethargy and loss of appetite

Treatment & Biosecurity 


Outbreaks of influenza are most common when large numbers of young horses are brought together in stressful conditions e.g. transporting together, sales or shows. Biosecurity measures needs to be strictly followed in these circumstances. Since the infecting strain of the virus tends to vary, vaccine manufacturers are constantly updating their vaccines to ensure full protection.


The disease can develop into life-threatening bronchitis or pneumonia. Often when horses recover from influenza they can be left in a debilitated state making them more susceptible to secondary infections. Lethargy and loss of appetite can last weeks to months, impacting the horse’s performance