WRANGLING ON THE RANGE #96
Does Your Horse Have HEAVES?
learn what can be done to manage this chronic lung
condition. BY BARB CRABBE, DVM
That nagging little cough at the beginning of your rides, and
that occasional runny nose ... could they mean your horse is
suffering from recurrent airway obstruction, or RAO?
Possibly. This condition, commonly known as heaves, is the most
prevalent lung disease seen in horses. It's chronic and can
threaten your horse's long-term health and performance. Although
heaves can't be cured, and severe cases are difficult to manage,
catching it early will help you manage it as well as possible,
and perhaps minimize its damage to your horse's lungs.
Here, I'll give you a checklist of symptoms to help you know when
to alert your veterinarian, so he or she can begin treatment at
the earliest possible point. I'll also help you assess the
disease's severity, explain the different stages of treatment,
and give you tips on how to prevent heaves in the first place.
Heaves is an allergic-based disease that compromises your horse's
ability to breathe, similar to the way asthma affects humans.
When your horse is exposed to allergy-producing substances in the
air, such as dust and pollens, cells in his lungs react by
releasing chemicals that cause air-passage linings to swell,
thicken, and produce mucus. When he breathes, air gets trapped
within these thickened passages. He then must use extra effort to
expel this trapped air.
The more your horse is exposed to allergens, the more sensitized
his lungs become. (The disease is most common among mature and
As the disease progresses, your horse's airways become ever
thicker. More mucus is produced. He begins to cough as he
struggles to exhale. Thick mucus appears in his nostrils, and he
begins to labor with every breath. Bacteria can become trapped in
his airways, leading to a bacterial infection (such as
pneumonia), a common complication in advanced cases of heaves.
If your horse has two or more of the following signs of the
disease, it's time to call your vet for a definitive diagnosis
and treatment plan.
INCREASED RESPIRATORY RATE
Why it happens: Your horse is having difficulty expelling air
through his thickened airways, so he breathes faster than normal
at rest in an effort to get enough oxygen. His respiratory rate
will also likely be elevated more than normal after exercise.
How to ID it: Count your horse's breaths per minute at rest by
watching his sides move in and out as he breathes. His normal
respiratory rate at rest should be between 8 and 16 breaths per
minute; if it's higher, suspect a problem.
INCREASED ABDOMINAL BREATHING EFFORT
Why it happens: Your horse is forced to use his abdominal muscles
to push air out of his lungs because his normal breathing muscles
aren't strong enough to do the now-bigger job. How to ID it: As
your horse breathes, watch for abnormal abdominal-muscle action
around the belly near the flank. (Compare what you see with the
breathing effort of other nearby horses.) Also note the
appearance of the muscles on the sides of his belly-do they seem
enlarged compared to those of other horses? This could be a heave
line, a horizontal run of muscle development caused by his extra
breathing effort. Look for it about threequarters of the way down
from his spine, toward his belly.
Why it happens: His lung tissues are irritated from airborne
allergens, and he's trying to expel mucus.
How to ID it: Heaves-related coughing typically occurs at the
beginning of exercise, plus during feeding and stallcleaning time
when dust is in the air. Coughing continuously throughout the day
might also indicate heaves.
(Note: A cough accompanied by a fever could be due to a bacterial
respiratory infection, but that doesn't necessarily rule out
heaves. Your horse could be feverish because he has a
heaves-related, fever-producing illness, or a completely separate
but concurrent disease that causes a fever.)
Why it happens: Lung cells produce mucus as part of the allergic
response that's associated with heaves. (How quickly they do so
depends on how quickly the disease is progressing.) Mucus that
builds up inside your horse's lungs eventually passes down the
airways and appears in his nose.
How to ID it: Watch for a thick, cloudy discharge that builds up
in your horse's nostrils. (Note: Although a gunky discharge can
occur simply as a result of inflammation from your horse's
heaves, it can also indicate the presence of a complicating
bacterial infection. Your vet might obtain a sample from your
horse's airway to determine whether the mucus consists only of
inflammatory cells, or if bacteria are also present.)
ABNORMAL LUNG SOUNDS
Why it happens: The effort to force air out through narrowed air
passages results in wheezing.
How to ID it: This is usually best left to your vet, who's
trained to recognize and distinguish breathing irregularities
using a stethoscope. If your horse's condition is quite severe,
however, you might be able to detect wheezing if you listen
carefully. If his case is less advanced, you might be able to
hear wheezing when he breathes hard during exercise.
(Note: Don't confuse lung sounds with throat sounds, such as
roaring, which can be caused by an obstruction or by paralysis of
Why it happens: Your horse is expending extra effort breathing,
plus his body could be depleted of oxygen.
How to ID it: Evaluate the muscle and fat layer covering his
ribs, spine, and hips. If the underlying skeletal structures
become more prominent, your horse is losing weight. (Tip: To
monitor your horse's weight, consider checking him monthly using
a weight tape.)
Treatments for Heaves
Once your vet has confirmed your suspicion that your horse has
heaves, plus determined whether the case is mild, moderate, or
severe (see "How Bad Is It?," opposite page), he or she will
recommend a treatment plan. To help you understand the available
options, I've outlined the typical treatments.
STAGE I TREATMENT: MILD HEAVES
You've caught the condition early and might even have a chance to
halt its progress. Treatment will consist simply of limiting your
horse's exposure to allergy-producing dust and other
particulates. (Note: Keep up these Stage I treatments a
even if your horse is also undergoing those in Stage 2 or 3.
These management measures are the most important actions can take
to protect his lungs.)
* Turn him out as much as possible. Being in open, ;s fresh-air
areas will limit his exposure to common barn dust 3r and other
airborne particles that can worsen his condition.
* Provide good ventilation inside. If your horse must
stay mostly in the barn, put him in a stall at the end of er. the
aisle where there's good airflow, and leave doors and windows
open as much as possible. When hauling, make sure the trailer is
well-ventilated and clean of bedding that might fly around
(rubber mats can provide needed cushioning).
* Feed him 'chest-high'. Placing feed on the ground ups your
horse's exposure to dust, while feeding from a hay bag or rack
placed above his withers can promote the inhalation of hay and
dust particles. A chest-high feeder avoids both these scenarios.
* Wet his hay. Sprinkling it liberally with water or even soaking
it just before feeding cuts down the dust.
* Consider pellets instead. If moistened hay fed at the correct
level doesn't bring improvements in your horse's condition,
consider feeding a pelleted forage ration, possibly moistened,
* Moisten his bedding. Spray a fine mist of water over the
surface of his stall every time you clean it (ideally once or
even twice daily). Avoid the dustiest beddings, such as wood
shavings. Shredded-paper beddings might be a good option.
* Don't 'clean around' him. Stall-cleaning stirs up particulates,
so remove your horse before cleaning his stall.
* Avoid dusty and/or indoor arenas. Ride outside or in
a well-watered arena. When trail riding, go in front to avoid
"eating the dust" of others.
STAGE 2 TREATMENT: MODERATE HEAVES
If your horse is showing moderate signs of heaves, or if there's
no improvement in his mild signs with Stage I treatments in
place, your vet could recommend one or more of the following
treatments. (Note: If you show, consult your association's
rulebook to determine whether any of the following substances are
* Oral corticosteroids. These will help control the inflammation
of the airways that occurs in response to allergy-producing
substances. This, in turn, reduces airway thickening and mucus
production. Two commonly used oral corticosteroids are
dexamethasone and prednisone.
Dexamethasone is the most potent and therefore the most
effective, but also has a higher risk of side effects, including
founder. Your vet might recommend it as an initial treatment to
get your horse's symptoms under control. Prednisone is less
potent but safer; it's more likely to be recommended for
long-term use, often after treatment's been started with
* Oral bronchodilators. These medications help relax the muscles
that cause your horse's air passages to spasm and close; this, in
turn, helps dilate and open airways to make breathing easier.
Clenbuterol is an effective oral bronchodilator.
* Expectorants. These break down and thin mucus, making it easier
for your horse to expel it from his lungs. This clears the way
for more normal breathing, plus helps eliminate bacteria that
could be trapped in the lungs.
There are a variety of over-the-counter expectorants, such as
Tri-Hist or Spec-Tuss, available from your feed store or
your vet. In more serious cases, your vet might prescribe
potassium iodide, a strong, highly effective expectorant. Make
sure your horse also has plenty of fresh, clean water, which
helps to loosen secretions naturally.
* Antibiotics. These might be needed if a bacterial infection is
complicating your horse's heaves. Ideally, your vet will collect
a sample from your horse's airways in order to target the
specific organism with the most appropriate antibiotic. (Tip:
Oral feed supplements marketed to help horses with respiratory
problems could also be beneficial. Ask your vet if he or she
would recommend one.)
STAGE 3 TREATMENT: SEVERE HEAVES
If your horse is showing signs of severe heaves and/or hasn't
improved with either Stage I or Stage 2 treatments, your vet
might recommend inhaled medications. You'll place a specially
designed mask (such as the Aeromask, by Trudell Medical
International) over your horse's nose several times a day to
deliver medication directly to his lungs for maximum effect. This
allows lower doses of drugs to be effective, thus lessening the
risks of side effects. (Note: Your vet might also recommend
expectorants and antibiotics, as in Stage 2 heaves.)
* Inhaled corticosteriods. Like their oral counterparts, these
medications help control inflammation and reduce airway
thickening and mucus production.
* Inhaled bronchodilators. Like their oral counterparts, these
drugs help open your horse's airways. Your vet will recommend
that you administer the bronchodilator first, then wait a period
of time for your horse's airways to open before administering the
corticosteroid. That way, the latter can reach as deeply into
your horse's lungs as possible for maximum effect.
To be continued from time to time