Equestrian topics

Equine Influenza

Hi! In this era of epidemics in humans and animals, who can forget the 2018/2019 outbreak of equine influenza in the UK?

I wanted to gather some information about the disease, so that the horse owners who read this blog are prepared next time. So, what is equine influenza (or horse flu or equine flu)?

Based on the definitions provided by the World Organisation for Animal Health, it is a “highly contagious though rarely fatal desease of horses, donkeys and mules and other equidae”.

Outbreaks of the disease have been recorded throughout history, severely affecting the economies that rely on horses as draft animals. Although most contemporary economies are not heavily reliant on equines, outbreaks of equine influenza impose a serious impact on the equestrian industry.

Equine influenza is an RNA virus with two main sub-types; H7N7 and H3N8. Both are type-A influenza viruses and are related to but differ from human and avian influenza viruses.


According to World Organisation for Animal Health and the American Association for Equine Practitioners, the symptoms of the equine flu include the following:

  • Temperature up to 41 Celcius
  • Nasal discharge
  • Harsh dry cough which may last up to six weeks
  • Depression
  • Loss of appetite
  • Weakness
  • Slightly enlarged retropharyngeal lymph nodes
  • The affected equines may also develop secondary infections, such as pneumonia
  • More severe cases may sometimes lead to permanent disabilities.

The incubation period of the virus is between three and five days. The average duration of the disease is ten to fifteen days, yet it can take a horse up to six months to return to its previous athletic commitments.


Image from pixabay.com

The most common way of transmission is through coughing and snorting of infected horses, which can spread the virus in a radius up to fifty yards.

Other ways of transmission include direct contact with the infected equine or its equipment (tack, brushes etc.).

Risk factors

A number of different factors can increase the risks of an equine getting infected with equine influenza:

  • Kind of equid: mules and donkeys face a higher risk in general
  • Age: young equines aged between one and five years old are more vulnerable to the disease than older horses and their cases are generally more severe than these of older equines
  • Place: areas where lots of horses gather, such as race tracks, showing grounds and veterinary hospitals
  • Immune system: weak immune system as a result of traveling, hospitalisation, training and showing

Public Health Risk

Experiments have shown that there is some low possibility of transmission of the horse flu to humans, but there have been no incidents of humans getting ill after exposure to the virus.

Yet it has been found that the strain H3N8 of the virus may infect canines.



It is advised for the infected equine to receive rest and supportive care.

Non-steroidal anti-inflammatory medication is provided if the temperature exceeds 41 Celcius.

In case of complications such as pneumonia or persistent fever, antibiotics can be administered.

The space around the infected horse needs to be disinfected too, which can be easily done with the use of disinfectants. As for the protection of humans who are in contact with the equine, alcohol hand sanitizers are effective.


Vaccination and yearly boost shots are the only known effective prevention of the disease. Nevertheless, as a 2019 report by Animal Health Trust showed, vaccination does not always guarantee full immunity against the virus.

So, that’s it for now. I hope this post is helpful.

Have you ever faced a case of equine flu? Feel free to share your experience with a comment!


  • American Association of Equine Practitioners (2017), “AAEP Infectious Disease Guidelines: Equine Influenza” , https://aaep.org/sites/default/files/Guidelines/EQUINE%20INFLUENZA_Final.pdf [20 November 2019)
  • Animal Health Trust (2019), “Equine Influenza Outbreaks Report in 2019”, https://www.aht.org.uk/wp-content/uploads/2019/04/Equiflunet-outbreaks-to-15-April-2019.pdf [Accessed: 8 March 2020]
  • The British Horse Society (2019), “UK Equine Influenza Outbreak”, https://www.bhs.org.uk/our-charity/press-centre/news/2019/february/equine-influenza [Accessed: 8 March 2020]
  • World Organisation for Animal Health (n.d), “General Disease Information Sheets: Equine Influenza”, https://www.oie.int/doc/ged/D14001.PDF [Accessed: 8 March 2020]

More Reading on Equine Influenza

  • American Association of Equine Practitioners (n.d.), “Equine Influenza”, https://aaep.org/guidelines/vaccination-guidelines/risk-based-vaccination-guidelines/equine-influenza
  • Singh, Raj K. et al. (2018), “A Comprehensive Review of Equine Influenza Virus: Etiology, Epidemiology, Pathobiology, Advances in Developing Diagnostics, Vaccines, and Control Strategies”, Frontiers in Microbiology, 9:1941, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6135912
  • World Organisation for Animal Health (2019), “OIE Expert Surveillance Panel on Equine Influenza Vaccine Composition, OIE Headquarters, 4 April 2019: Conclusions and Recommendations”, https://www.oie.int/en/scientific-expertise/specific-information-and-recommendations/equine-influenza

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