How to Diagnose Heaves in Horses

Three Parts:Recognizing Breathing-Related Symptoms of HeavesObserving Other Heave SymptomsGetting a Veterinary Diagnosis

Heaves is a respiratory problem that commonly affects adult horses.[1] It occurs when a horse breathes in particles from the environment, called allergens, that cause an allergic reaction in the respiratory tract. This allergic reaction narrows and obstructs a horse’s airways, making it harder for the horse to breathe.[2] Heaves can range from mild to severe. Mild heaves can become severe, so it is important to recognize heaves as soon as possible so a horse can receive proper treatment.[3]

Part 1
Recognizing Breathing-Related Symptoms of Heaves

  1. Image titled Diagnose Heaves in Horses Step 1
    Watch your horse breathe. Normal breathing for a horse is quiet and doesn’t require much effort. Horses with heaves, though, will have trouble breathing, particularly during exhalation. Your horse will have trouble getting air out of his lungs, so his exhalation will be prolonged and difficult. The extra effort to exhale will require him to use his abdominal muscles, causing those muscles to get larger.[4][5]
    • A horse’s normal breathing rate is 8 to 12 breaths per minute. If your horse has heaves, his breathing rate may be as high as 36 to 40 breaths per minute.[6] Count your horse’s breaths for a minute to determine his breathing rate.
    • Your horse may have trouble breathing even when he is at rest.[7]
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    Locate a heave line on your horse. A heave line, which runs along the bottom edge of a horse’s rib cage, is a telltale symptom of heaves in horses. It forms when the abdominal muscles get larger from the continued effort to exhale.[8] Don’t look for the heave line on your horse right away—it will take some time before his abdominal muscles enlarge enough to form the line.
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    Listen to your horse breathe. As you watch you watch your horse breathe, listen to his breathing sounds. With a severe case of heaves, your horse will wheeze when he breathes.[9] If he has mild case of heaves, he may not make any noise when he breathes.[10]
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    Observe your horse’s coughing. Within the lungs, the airway inflammation caused by heaves produces mucus.[11] This mucus can block the airways, causing your horse to cough to get the mucus out. Early on in the disease, the cough will be occasional, such as during feeding or exercising. It may or may not produce mucus.[12]
    • The cough with a severe case of heaves is very deep and produces pus-like mucus.[13]
    • Your horse's cough may become chronic.[14]
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    Look at your horse’s nose. With all of the extra mucus in your horse’s airways, he may develop nasal discharge, which could look thick and ropy.[15] In addition to discharge, your horse’s nostrils may flare when he breathes because of the increased breathing effort.[16]
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    Watch for ‘asthma attacks.’ Heaves in horses is similar to asthma in humans. If a heaves-prone horse is stabled indoors, he may have exaggerated responses to environmental allergens.[17] These responses can look like human asthma attacks, in which your horse would have sudden fits of troubled breathing.[18]

Part 2
Observing Other Heave Symptoms

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    Determine if your horse is exercising less than usual. Horses are very athletic animals. A horse with heaves, though, will have decreased athletic performance. If your horse has a mild case of heaves, he will not be able to exercise as much as he used to, and will take longer than usual to recover after exercise.[19] You may need to spend more time cooling him down after exercise.
    • An inability to exercise in horses is called exercise intolerance. This intolerance will vary according to the severity of heaves.
    • For some horses, the only sign of heaves is decreased athletic performance.[20]
    • If your horse cannot exercise, do not force him to. This would make it even harder for him to breathe.
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    Take note of a decreased appetite. As with other animals, horses need a proper diet to be healthy and maintain a good overall body condition. In severe cases of heaves, a horse can become unable to eat because of the struggle to breathe.[21] If your horse cannot eat, he will lose weight.[22]
    • At mealtimes, watch your horse to see if he is able to eat.
    • Your horse may also drink less water than usual.
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    Observe changes in your horse’s behavior. The struggle to breathe can make your horse anxious or agitated.[23] Neighing (a high-pitched sound) may indicate anxiety in your horse.[24] Quick and aggressive tail swishing can indicate agitation.[25]
    • Your horse may also paw or stamp at the ground with his hooves if he’s feeling uncomfortable.[26]

Part 3
Getting a Veterinary Diagnosis

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    Take your horse to your vet. Heaves requires a veterinary diagnosis.[27] Since a mild case of heaves can become more severe, an early diagnosis could help your horse receive treatment before heaves causes serious health consequences.
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    Provide a detailed history of your horse. Your vet will primarily use your horse’s history and a physical examination to diagnose heaves.[28] The more information you can give your vet about your horse, the better. Important details of your horse’s history include his overall health (e.g., current and previous diseases), diet, housing environment, and when you first started noticing his breathing problems.
    • Straw and hay contain allergens that commonly cause heaves in horses.[29] If you use straw or hay for your horse’s bedding, your vet will need to know.
    • Tell your vet if your horse’s heave symptoms get worse at certain times. For example, heave symptoms can get worse when a horse is stabled, or out to pasture during the warmer months.[30]
    • Cleaning the barn can release dust particles into the air that can worsen your horse’s heaves. Tell your vet often how you clean the barn.
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    Have your vet physically examine your horse. Your vet will perform a thorough physical examination of your horse. To listen to your horse breathe, your vet may place a bag over his muzzle. The bag would cause your horse to re-breathe carbon dioxide and make him breathe more deeply, allowing for louder breathing sounds.[31]
    • When listening to the breathing, your vet will hear wheezing, as well as rattling noises in the trachea.[32]
    • Your vet will also assess your horse’s overall body condition, especially if he has been unable to eat.
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    Allow your vet to collect a fluid sample. If your vet thinks your horse has mild to moderate heaves, then additional testing would be needed to provide more information about the extent of disease. A technique called bronchoalveolar lavage (BAL) is very useful for diagnosing heaves. BAL allows your vet to take a fluid sample from your horse’s lungs to analyze the inflammatory cells in the fluid.[33]
    • To perform BAL, your vet will sedate your horse and pass an endoscope or small tube through his nostrils down to his lungs. Your vet will then pass a saline solution down through the tube and pull it back up to collect the fluid sample.[34]
    • BAL is not recommended for horses who have severe breathing problems at rest.[35]
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    Discuss the need for chest x-rays and blood work. In many cases of heaves, x-rays and blood work are not necessary to make a diagnosis. In particular, blood work is usually normal with heaves.[36] Chest x-rays can help rule out other possible causes (e.g., pneumonia, tumors) of your horse’s breathing troubles.[37]


  • Heaves is a non-infectious disease, meaning that infectious agents (e.g., virus, bacteria) do not cause it.[38]
  • Heaves used to be known as chronic obstructive pulmonary disease. It is now known as recurrent airway obstruction.[39]
  • Dust, mold, hay and pollen are allergens that can cause heaves in horses.[40]
  • Heaves can occur in any sex and breed, and can be hereditary. Around 12% of adult horses have some degree of allergen-induced lung inflammation.[41]

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Categories: Horse Health