Most horses and foals will develop mild to moderate respiratory infections at some point in their life. Often horses and foals that are stressed, have other viral infections, are on poor feed or have parasite infestations are more likely to develop respiratory infections as the body is just not able to fight off the virus or bacteria that causes the problem.
Many diseases such as the equine herpes viruses strains 1 and 4, equine influenza or the horse flu, and equine viral arteritis that are viral infections will cause upper respiratory problems in horses. The symptoms of these viral infections typically range from discharge from the nasal passage, coughing, going off feed, lack of energy, problems in breathing to more serious conditions such as collapse and even death in severe cases. Viruses can often be vaccinated against, but it will not always prevent all the symptoms. In most horses the symptoms will be greatly reduced as will the length of the viral infection since the body already has antibodies built up to combat the virus. In some horses, particularly Arabians, there are some immunosuppressing genetic conditions that will prevent the foals from developing normal immune systems, leading to fatal results.
Just like people, horses can get upper respiratory infections from other horses. Horse that are shown, trailered or stabled with other horses are more likely to have the viral infections or even bacterial infections than horses that are kept on the same pasture in a controlled area with familiar, vaccinated horses.
Bacterial infections that result in respiratory infections are usually secondary in nature and develop as a complication or further problem from a viral infection. Bacterial infections are noted by a thick discharge from the nose, elevated fever that will often last for long periods of time, depression, lack of appetite and unwillingness to exercise. The horse may cough up material known as a wet or productive cough, but may also develop a hacking, dry cough. In some cases the secondary infection leaves lasting damage to the lungs, trachea and upper respiratory tract.
Strangles is also a bacterial infection of the respiratory tract that is very serious. The horse will have a heavy discharge of mucous material coupled with inflammation of the membranes of the nose and throat. Often the lymph nodes become so inflamed they rupture, producing a very thick, white discharge. Young horses under five years of age are most prone to this highly contagious infection and several horses in one herd may have the infection at the same time. Typically the abscesses that are causing the breathing obstruction or swelling will break on their own, if not they can be lanced. Antibiotics will help speed the process but horses can still die because of the condition of the complications that can occur with the disease.
Respiratory infections in horses can be minimized by vaccinations, feeding good quality dry hay or feed that is free from dust and mold, and limiting your horses contact to any horse that appears unhealthy, has a nasal discharge or cough.
If you suspect an upper respiratory infection contact your vet to determine the cause, then use the appropriate therapy and treatment to minimize any complications or long term problems that can occur.