Inflammatory Airway Disease in Performance Horses
Dr. Melissa Mazan
When did you first notice a problem?
One thing that you might notice is that your horse has more difficulties on hot, humid days than on clear, cool days. Often the problems are seasonal as well. This is similar to people with asthma or other chronic respiratory diseases. When the health bulletins on the radio start warning people with respiratory diseases to stay inside and to use air conditioning, you may notice that your horse has difficulty breathing as well.
Some horses with IAD simply have mild signs of exercise intolerance. A jumper may start knocking down rails, or may not make the times that he used to do easily. Dressage horses often show a reluctance to come into a frame. Horses have enormous respiratory reserves, however, and dressage horses, hunters, and lower level jumpers don't work at peak aerobic levels despite being highly trained athletes. This is why they usually are diagnosed when they are at a more advanced stage of disease, showing classic signs of IAD as we noted earlier.
Horses who work at peak exercise, such as racehorses, polo ponies, or high level event horses, usually show signs at an earlier stage of disease. Racehorses may be a tenth of a second slower than previously – this doesn't sound like much, but it translates into being 2-3 lengths behind a horse that they could previously have beaten. Oftentimes, racehorses are described as having 'hit the wall' at the 3/4 mark. A high goal polo pony might not be able to ride off his opponent when he is nearing the end of a chukker. These signs may be subtle, and it is not immediately obvious that the culprit is the respiratory system.
History. Your veterinarian will start with a careful medical history. Questions that are important include:
What signs and symptoms did you notice?
How is your horse stabled?
Is the housing new or old?
Is there good ventilation?
Has your horse moved recently?
Does your horse live adjacent to an indoor arena?
Where is the hay stored?
Is the hay overhead or in a separate building?
What does your horse eat?
Has the hay source changed?
Is the hay of good quality?
When are your horse's symptoms the worst?
Do you notice a problem more in the winter or summer?
Do any other horses in the barn have the same symptoms?
Has your horse had a respiratory virus in the last 3 to 6 months?
Has your horse been treated for this problem before?
If so, has he had a good response to any treatments?
Your veterinarian will conduct a thorough clinical examination, which should include the following:
Breathing assessment. Your veterinarian will visually assess your horse's breathing while he is resting to look for any abnormal expiratory effort, increase in respiratory rate, or evidence of difficulty breathing. She will listen to your horse's respiratory system, from the trachea to the lungs, using a stethoscope. She should hear normal respiratory noises, but if your horse has a more advanced stage of IAD, she may hear musical sounds, especially on expiration, called wheezes.
Your veterinarian will palpate your horse's larynx in order to see if she can elicit a cough and will probably want to assess your horse's respiratory system after exercise, as well. Oftentimes, your veterinarian will use a rebreathing bag to assess your horse's ability to take a deep breath.
Temperature. In order to make sure that your horse doesn't have an infectious respiratory disease, your veterinarian will take your horse's temperature.
Blood tests. She may also choose to do blood tests to look for any signs of infection.
Endoscopic exam. Your veterinarian may choose to look at your horse's trachea using an endoscope – horses with IAD often have an excessive amount of mucous in their airways. You don't always see this externally, because horses are quite adept at coughing up this mucous and then swallowing it.