We are a Royal College of Veterinary Surgeons (RCVS) approved equine hospital.
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Equine Influenza, 'flu', is caused by an influenza virus similar to the ones that effect people (but horses cannot be infected by human influenza or vice versa). Viruses are tiny infectious particles that can produce disease, although they can only replicate inside another cell. All influenza viruses undergo frequent genetic changes to produce different strains, which make it tricky and expensive to produce up-to-date commercial vaccines against the current strain. As a result, the vaccines that are available may not provide full protection against any new strain of the virus, however, vaccinated horses are much less severely affected by the disease, so vaccination is extremely worthwhile.
Equine flu is highly contagious and is acquired mainly by the inhalation of the virus, via aerosols, from other infected horses or via virus-containing droplets in the horse's environment. In short, affected horse's coughing and spluttering will spread the virus.
Indirect spread is also possible via feed or water buckets, or grooms / handlers / nurses / vets or anyone who has contact with an affected horse. Unlike strangles and some other infections, the flu virus does not linger nor survive for long outside the horse.
Once a horse has breathed in the virus, it invades the lining epithelium of the airway, which becomes swollen and inflamed producing a very sore throat and a nasty cough. The virus replicates mainly in the upper respiratory tract and the viral damage causes the surface membranes lining the airways to ulcerate. Clinical signs are due to this local tissue damage and the whole body's inflammatory and immune response to the infection. The damage of the surface layers of tissue in the repiratory tract can disrupt the clearance of mucus and other debris from the airways. In turn these damaged areas end up being invaded by bacteria and further infections ensue.
Antibiotics have no effect against a virus, but they can be useful to control secondary bacterial invasion. This is a particular risk in foals that can succumb to a fatal pneumonia.
Clinical signs of equine flu in horses are variable, but include the following:
Equine flu in general has a has a fairly short incubation period, with clinical signs usually appearing within 1-5 days after exposure. It is generally a self-limiting disease resolving within 3-6 weeks, provided that horses are well managed. Horses may also experience persistent poor performance syndromes after the initial acute phase of infection.
All horses with respiratory infections should be given complete rest. Ideally, they should not recommence any strenuous exercise until two weeks after the signs have gone. Frequently the advice is given that they should have a week off for every day that they have had a fever (raised temperature), but many riders will find that their horses are below par for longer, in the same way the people can feel run down after flu.
Good stable ventilation and management is essential. Exposure to dust and spores should be minimized as horses with respiratory infections are susceptible to developing further airway inflammation. If hay is fed, it should be of good quality and soaked. If weather conditions permit, affected horses benefit from being turned out into a small paddock for at least part of the day once their temperatures have returned to normal. This is especially important in the recovery stages.
Some of the new antioxidant feed supplements on the market to help respiratory function, may well be of benefit, as well as some other medications to help breathing. It is best to consult your own vet for the appropriate treatment of individual cases.
An accurate diagnosis can be made by:
As soon as a horse shows any suspect signs, strict hygiene and isolation procedures should be applied. Any horses that have been in contact with the affected horse should be carefully monitored and ideally should not attend shows or any other competitions as they may be incubating the disease. Exposure to the virus combined with the stress of travelling will make infection more likely.
The disease is spread by inhalation of virus released into the atmosphere as an aerosol by coughing and blowing, essentially one horse coughing over another. For this reason equine flu is highly contagious within a group of horses.
If you suspect your horse has equine influenza you should contact your vet. Steps can then be taken to stop the spread of the disease. One of the most crucial is identifying the infection accurately; if you know what you are dealing with, then you can control it.
Equine flu is difficult to control, especially in horses that are frequently transported and mixed extensively. Outbreaks are most common when young, susceptable horses are brought together at sales, shows or for training. Regular vaccination is the key to the prevention and control of outbreaks of equine influenza and is compulsory under British Horseracing Authority (BHA) and International Equestrian Federation (FEI) rules in the UK.
Various equestrian regulatory bodies have slightly different rules regarding vaccination. Please chesck with your own regulatory body to ensure that your horse's fly vaccinations comply. Broadly speaking the regulations are:
To compete, horses require booster vaccinations not more than 365 days from their last vaccination. Horses must not have been vaccinated less than 7 days before a competition. Horses competing under FEI rules must have received a booster vaccination not more than 6 months + 21 days prior to competing.
Please check that all vaccinations are up to date. In the face of a local outbreak, it may be advisable to give a booster to any horse that has not been vaccinated in the previous 6 months. Maximum immunity is not reached until about 2 weeks after the vaccination.
If you have any questions or concerns, please speak to one of the vets at BELL EQUINE on 01622 813700.
During the course of the 2018-19 equine influenza outbreak, we had many questions about equine influenza vaccines. Influenza does occur from time to time every year, and is most commonly reported in unvaccinated horses.
The detection of influenza in a small number of vaccinated horses led some people to question whether vaccination is worthwhile.
Following expert advice, we believe that vaccination is essential to controlling equine flu and is particularly important during an outbreak. All horses’ immune systems respond slightly differently to the flu vaccine and flu can vary a little from strain to strain, so predicting the exact response to an infection can be difficult but vaccination remains by far the most important way of controlling this disease
Experience from recent outbreaks shows that even in situations where vaccine protection is not 100% the vaccines are still helpful by reducing the severity of the symptoms, reducing the time that the horse is ill for and reducing spread of disease.
Spread of flu through unvaccinated groups of horses is often rapid, horses generally have more severe symptoms and take longer to recover. In rare cases it can be fatal.
Vaccination works by mimicking the effects of infection using dead/deactivated virus or parts of the virus. The horse’s own immune system then comes to recognise the virus and is primed and ready if it meets a real flu virus. The vaccines are produced and updated using expert scientific guidance to cover the strains of flu that they think our horses are most likely to be exposed to.
By boosting vaccination the immune system remains primed. The frequency of boosters will be determined by the level of risk the horse is exposed to. At present we advise vaccination for all unvaccinated horses and booster vaccination for any horse that has not had a vaccination within the last 6 months. Please feel free to call the clinic should you wish to discuss your horse’s vaccinations and individual situation.
The outbreak of equine ‘flu in North Kent in early 2019 follows the outbreak of cases in the later part of 2018 and 2019, which caused the British Racing Authority (BHA) to cancel racing across the UK on 7th February 2019 for the first time in 18 years. BBC Sport posted an article regarding this decision which you can read HERE.
The Animal Health Trust (AHT) informs us on the most recent outbreaks of equine influenza. They regularly update their dedicated equine ‘flu page EQUIFLUNET with the most up to date information as it comes through.
The British Equestrian Federation (BEF) also has a very useful GUIDE on biosecurity and Q&A on equine flu.
We would like to take this opportunity to encourage everyone to be vigilant to minimise further disease spread and to protect your horse from the disease in the future. Please ensure that all horses are up to date with their vaccinations and have any lapsed or unvaccinated horses vaccinated as soon as possible. While annual vaccination should protect the majority of horses for at least one year, we recommend a booster vaccination if your horse has not received a vaccination in the last 6 months, especially for certain at risk individuals.
Please discuss your horse’s individual risk with your vet and be on the lookout for clinical signs of fever and signs of respiratory disease (nasal discharge, coughing and fast breathing).
Do not hesitate to contact us on 01622 813700 if you have any questions or concerns. Our vets will be happy to help.
We advise that the frequency of vaccination should depend on the risk to the horse. All horses should be vaccinated at least yearly. Horses at higher risk, in particular those that mix for competition or are stabled on yards with frequent new arrivals should receive boosters every 6 months.
PLEASE NOTE THAT SOME COMPETITION BODIES HAVE UPDATED THEIR VACCINATION RULES TO REQUIRE HORSES TO HAVE HAD A VACCINATION WITHIN THE LAST 6 MONTHS. PLEASE CHECK VACCINATION RULES IF YOU INTEND TO COMPETE
for example:
British eventing: please click HERE to go to their website.
The Pony Club: please click HERE to go to their website.
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