Equine 'Flu

Equine 'Flu

As the British horse racing industry is currently in lockdown, it’s a timely reminder that Equine ‘Flu is a serious infection that can be fatal. We examine the causes, symptoms and precautions that you can take to minimise the risk to your horses, ponies and donkeys.

What causes Equine ‘Flu?

Equine ‘Flu is caused by viruses just as human ‘Flu is and is endemic in the British horse population. Thoroughbred horses and other competing breeds have to be vaccinated against the infection and so outbreaks are rare. There are different strains of ‘Flu virus that cause the infection and the vaccines developed usually protect horses against the infection but occasionally a known virus can mutate slightly and cause mild symptoms in vaccinated horses. Developing new vaccines for new ‘Flu virus strains can take years according to the Animal Health Trust, with the current vaccine developed for known viruses at least 15 years ago.

What are the symptoms of Equine ‘Flu?

The infection is a highly contagious respiratory disease that can be carried on our clothes, shoes, tack and equipment in a yard, and be spread through particles in the air when an infected animal sneezes or coughs. It is often transmitted when horses rub noses and can infect horses, ponies and donkeys. The virus doesn’t survive well in the environment and can be killed by heat cold and disinfectants. It has been demonstrated that wild birds can also transmit the disease to horses (MSD Animal Health). The infection incubation period is short at 1-3 days and the severity of the symptoms will depend on the health, age and vaccination status of each horse. Vaccinated horses will usually have less severe symptoms but can still pass it on to other horses. The infection causes a high temperature or fever of up to 41.1 degrees C, loss of appetite, depression, clear nasal discharge (snot), a harsh, dry cough and enlarged lymph nodes in the head and neck.

In mild cases these symptoms usually clear up in 2-5 days, but secondary bacterial infections such as pneumonia could delay recovery for weeks or months.

Preventing Equine ‘flu and reducing the risk of spreading the infection

The best prevention is to get your horses vaccinated regularly and ensure you always follow good hygiene practices. It’s important your horses are adequately fed to ensure they have a robust immune system, they are as stress free as possible and that any new horses to a yard are isolated for 2-3 weeks to make sure they are healthy before they meet their new stable mates.   If you can keep more susceptible animals (foals, mares and older horses) separate from those that travel to events, all the better.

If you suspect any of your horses may have contracted the disease isolate them immediately and ensure the strictest hygiene control is in operation with no sharing of buckets, tack, or any equipment takes place. It’s also good practice to use disinfectant to clean boots and hands and change clothes when leaving an infected animal before going near healthy animals. Always consult your vet for up to date advice and don’t expose your horse to other healthy animals until they have the all clear from the vet.       

Caring for an infected horse

There is a general rule of thumb that a horse that has a fever should be rested for 1 week for every day of fever, with a minimum of 3 weeks rest with no strenuous activity at all. This will allow time for their respiratory system to recover. Your vet may prescribe anti-inflammatory drugs to help control the fever and if the fever lasts longer than 3-4 days antibiotics might be prescribed if a secondary bacterial infection is suspected. (Merckvetmanual.com)


You can also help your horse overcome the infection by symptoms by controlling dust, ensuring their stable is well ventilated and ensuring they are well fed.


The good news is vaccinated horses will usually only display mild symptoms and recover within a few days, but always consult your vet for a diagnosis and care advice and monitor your horse’s condition carefully. You might want to consider insuring your horse’s health so if the worse happens and you need vet care you won’t have to worry about the cost.