Equine influenza is a highly contagious and common disease. It is caused by a virus that infects the airways and lungs. This causes respiratory problems. Basically, influenza occurs in horses of all ages, but young and older horses are especially susceptible to it.
Some horses are infected without you noticing it, they show no symptoms. The horses that do suffer show typical symptoms such as fever, watery nasal discharge, dry cough, lethargy and poor appetite. The viral infection can result in a bacterial infection. The virus damages the horse’s mucous membranes, giving bacteria a chance to cause an infection. The horse will then have thicker nasal discharge and more of a gurgling cough. The horse may develop chronic respiratory problems from this. Typically, a horse will be sick for 2 to 10 days. Once there is a bacterial infection it will last longer.
As we already mentioned in the introduction, influenza is a highly contagious disease. It is mainly spread through direct contact with the nasal discharge, so contact between horses. It can also spread through indirect contact (through clothing, brushes, human contact) and through fluid particles in the air (through coughing, sneezing). The virus can spread rapidly, an entire barn can become infected in a few days. A horse is still contagious to other horses up to 5-6 days after infection. Therefore, it is important to isolate a sick horse and ensure proper hygiene to prevent further spreading.
A horse with influenza is ideally treated with an antipyretic and antibiotics for several days. In addition, it is wise to give the horse rest in an airy environment such as pasture or paddock. Most horses will recover fully, but in extreme cases chronic problems such as heaves may develop. For foals that have not received enough antibodies through the mother’s colostrum, there is a risk of death from influenza. Adult horses rarely die from this disease.
You can prevent influenza by vaccinating your horse against it. This vaccination offers protection against the symptoms but not against infection with the virus. This means that vaccinated horses can still be carriers of the virus and infect other horses. Therefore, it is important to vaccinate the entire barn at once. The primary course of vaccination for influenza consists of three vaccinations, with a period of 3 to 12 weeks in between. After that, a six-monthly or annual vaccination is required. In the Netherlands, an annual vaccination is sufficient, but for international competition, a six-monthly vaccination is required. Foals can be vaccinated from the age of 4 or 6 months, depending on the dam’s vaccination status. If the mare has not been vaccinated or has not been vaccinated regularly, it is wise to vaccinate the foal at 4 months. If the mother was vaccinated in the last 4 months of gestation, you can wait until the foal is six months old. A horse is fully protected against influenza two weeks after the primary course of vaccination.