COPD in Horses

Chronic obstructive pulmonary disease (COPD) is also known as recurrent airway obstruction (RAO) or Heaves.  It is a problem that can be treated, but, once a horse has it, never cured.

With my mare, it began slowly, a cough when we would pick up the trot, then nothing more that day.  An occasional cough when she was in her stall.  Then it became several coughs while trotting, often bringing us back to the walk until she cleared her throat.  I blamed it on the cold, dry weather, added some oil to her feed, and soaked her hay in the barn at night.  The hay was a little dusty, but not moldy.

It seemed to do the trick; she stopped coughing and we could go back to full work.  About a month later however, she was coughing on a trail ride, couldn’t trot, and was coughing while standing still in her paddock.  I noticed that she, Indy, and several other horses in the barn weren’t finishing their hay.  Upon closer inspection I saw that we had gotten in a batch of hay that was not only dusty, but had mold spores in it as well.

Do you know what moldy hay looks like?  This is a drastic example; it may not be this obvious.  Smell it, feel it, shake it out.  If it makes you cough, don’t feed it!  Mold cannot be soaked out of hay – your best bet is to throw out the entire bale.

I of course was furious, as now my horse has a lifelong issue and will require more work to maintain on my end.  I decided to explore more into this affliction so I can best manage her.

COPD can manifest itself in numerous ways in the horse.  It most commonly shows as a cough which is caused by the horse trying to expel mucus through narrowed airways.  The narrowing can be caused by inflammation (due to irritation from allergens),  tightening of surrounding muscle, and thickening of the tissue surrounding the airway.  When the cells in the lungs are exposed to allergens, such as fungal spores, mold, and dust, the body responds by producing cells that thicken the tissue and produce mucus – the body’s defense mechanism.  Extra effort is required for the horse to bring their regular volume of air through these thickened, narrow passageways.  The more the horse is exposed to the allergen, the more sensitive the lungs become, the more difficult it is to breath.  This shows up as an increased respiratory rate (above the normal 8-12 breaths per minute) and a longer recovery after exercising.

Mucus forms not just in the lower airway, but throughout the upper airway as well.

In addition to the cough, horses may also develop nasal discharge.  The discharge comes from increased airway secretions – the body’s attempt to heal itself.  These secretions can also cause further obstruction of the airway.

The term heaves came from the increased respiratory efforts required by the horse, simply put, labored breathing.  These horses will often have a “tucked up” appearance, with a line of abdominal muscles called the “heave line”.  This is caused by the increased effort by the abdominal muscles to force the air out of the lunges during expiration.  When listening with a stethoscope, one will often hear wheezing when the horse breathes.

Abdominal muscles creating a “heave line”

An extreme complication of heaves is a bacterial infection (such as pneumonia) resulting from bacteria becoming trapped in the airway.

Diagnosis of this condition is based mostly on history.  Your vet will want to know when your horse has coughed and any discharge they have been having.  A physical exam may include a re-breather test, where a bag is placed over the horses nose for a brief period to increase their respiratory rate.  The vet will listen with a stethoscope for any abnormal breath sounds.  This may also induce coughing from your horse.

A Bronchoalveolar lavage (BAL) is another test that can be done, which would show whether or not there is inflammation in the lower airways and rule out infection.  This test is not usually necessary to diagnose COPD, but rather used to rule out other issues.

If your horse is displaying any of these symptoms, no matter how minimal, it is best to take action now before it gets any worse.  In my next blog post, I’ll talk about prevention and maintenance.


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