Transcript:

[0:01]

Hi everyone, welcome back to Mad Barn Academy, and if this is your first time tuning in, then welcome! We hope to earn your subscription today. I'm Dr. Fran Row, one of the veterinary nutritionists here at Mad Barn, and our topic for today's video is going to be on equine asthma — also commonly referred to as heaves.

[0:19]

Asthma is a relatively common condition seen in horses, and with the changing of seasons upon us, some of you may be preparing for your horse's asthma to flare up this wintertime. That’s why I thought this would be a great topic to cover today. So let's get started.

[0:40]

Asthma has had many different names over the years as we've come to better understand and characterize the disease process in horses. You may have heard it referred to as heaves, recurrent airway obstruction, chronic obstructive pulmonary disease, and maybe even inflammatory airway disease. The most up-to-date terminology is equine asthma, so that’s what I’ll be using throughout the rest of this video.

[1:09]

Asthma is a chronic, non-infectious, inflammatory airway disease in horses. The disease process is actually very similar to asthma in humans, and just like in humans, it's triggered by exposure to environmental allergens. When these allergens are inhaled into the lungs, the immune system overreacts in response, leading to inflammation, narrowing of the small airways (called bronchoconstriction), smooth muscle contraction (bronchospasm), and mucus accumulation.

[1:50]

Ultimately, all of this leads to what we refer to as chronic obstruction of the airways, resulting in respiratory difficulty. Here’s a visual of what’s happening in the lungs with a disease process like asthma. This is actually a human model, but the process is still the same, and I thought it was a great illustration showing the different elements of inflammation and narrowing.

[2:24]

On the left-hand side of the diagram, we see a normal airway. The smooth muscle around the airways is relaxed, allowing them to be open and dilated. There’s no evidence of inflammation or mucus. In the asthmatic airway, we start to see those elements that come with an overreactive immune response: bronchospasm, inflammation inside the airways, bronchoconstriction due to narrowing, and mucus accumulation. This makes it very hard for airflow to pass through — almost like breathing through a coffee straw compared to a regular straw.

[3:39]

Asthma most commonly develops during mid-age, between about 9 and 12 years old, although it can certainly develop earlier or later. While all breeds of horses can be affected, we now understand there is a genetic component. Foals born to one or both parents with asthma are more likely to develop it themselves.

[4:14]

For many horses, clinical signs of asthma tend to occur seasonally. We generally recognize two forms based on season: barn-associated asthma (occurring most often in winter and spring) and pasture-associated asthma (occurring in summer and fall). Horses with barn-associated asthma tend to react to allergens like molds and dust, with symptoms worsening in winter when they are indoors. Horses with pasture-associated asthma react more to plant and tree pollens, with symptoms worsening in summer when pollen counts are high.

[5:13]

Some horses remain asthmatic year-round, reacting to allergens in all seasons. Just like in people, it really depends on the individual.

[5:30]

Here are some of the most common clinical signs of equine asthma, which are fairly consistent between barn-associated and pasture-associated types, and can range in severity. You might notice increased respiratory effort or rate, even at rest. Horses may have flaring nostrils and more abdominal effort or push when breathing. This can lead to a “heave line” — a distinct line along the abdomen from overworked abdominal muscles pushing air in and out of the lungs.

[6:34]

Other signs include coughing (sometimes with mucus), wheezing or harsh breath sounds, exercise intolerance, lethargy, dullness, and even weight loss in more severe cases. Some horses appear normal at rest but cough or tire quickly during work. Severe cases can deteriorate into life-threatening respiratory distress, especially if the horse exerts itself or becomes stressed. Signs include bluish gums (cyanosis), collapse, and in rare cases, death.

[8:14]

When diagnosing asthma in horses, many cases can be identified based on history and physical exam alone. Your veterinarian will first want to determine if the respiratory disease is infectious (and possibly contagious) or non-infectious like asthma. They’ll ask about potential exposure to infectious agents — for example, if your horse travels, competes, interacts with new horses, or if a new horse has arrived on the farm. They’ll also check vaccination status, especially for respiratory illnesses like influenza and rhinopneumonitis.

[9:09]

Your vet will want a timeline of signs — when they began, if they recur seasonally, and whether they’ve worsened. With asthma, usually only one horse on the property is affected (although others may also be asthmatic), as opposed to an infectious outbreak where many horses become ill in a short time.

[9:48]

On physical exam, your vet is looking for those same clinical signs that we discussed two slides back, but they’re also going to perform a full physical — listening to the heart, the lungs, taking a rectal temperature, etc. When auscultating the lungs of an asthmatic horse, we’re expecting to hear abnormal lung sounds like harshness, crackles, or wheezes, and we expect those abnormal sounds to be present throughout the entire lung field and on both sides of the horse.

[10:19]

Lastly, your vet will confirm whether or not there’s a fever present. With non-infectious disease like asthma, the horse should not be febrile — so if they are, that might indicate we’re dealing with some type of infectious disease process.

[10:37]

Your vet may recommend additional diagnostics if your horse is very mild in symptoms, doesn’t quite “read the book,” or if you’re looking to confirm or rule out other issues. These will be case-dependent and at the discretion of the veterinarian, but might include bloodwork, upper airway endoscopy, a bronchoalveolar lavage, and potentially thoracic ultrasound.

[11:07]

Unfortunately, asthma is not a curable disease, but it is a manageable one. Treatment strategies are centered around proper management to reduce disease severity, and the use of medications when necessary to help control the disease. Environmental modification is the number one most important management factor for horses with asthma — we have to reduce the horse’s exposure to the offending allergens to be successful in controlling the disease. In the coming slides, we’ll talk about what some of those environmental changes look like.

[11:50]

Dietary support is also an important facet of management, as this provides the body with the building blocks it needs to support a normal immune response and lung health. Lastly, there are medications that can be prescribed to help improve respiratory function in asthmatic horses. It’s important to remember that while medications may seem like a quick fix, they will be less effective unless paired with other management strategies. Medications are certainly necessary for some horses at certain times of year, but the goal should be to use them when needed and not as a substitute for environmental modification.

[12:41]

Let’s go into more detail about management strategies for asthmatic horses, starting with environmental modification. I’ve broken these recommendations into four main categories. For horses with barn-associated asthma, it’s recommended they be housed outside 24/7, 365 days a year. Of course, if there’s severe inclement weather and they need to come in temporarily, do your best to minimize the time indoors and focus on making the barn environment more suitable. Be aware that an asthmatic horse might have a flare-up if kept inside for an extended period.

[13:30]

Conversely, horses with pasture-associated asthma should minimize time spent on summer pasture when allergen load is highest. This might mean increasing stalled time or using a dry lot during allergy season.

[13:48]

Regardless of type, when horses are indoors, it’s important to make the barn as suitable as possible to minimize allergen exposure and dust. Some recommendations include maximizing ventilation — keeping barn doors and windows open, even when it’s cold, and possibly moving the horse to a better-ventilated stall near a door. Remove the asthmatic horse from the barn during chores to avoid exposure to dust stirred up during cleaning, and don’t bring them back until the air has settled.

[14:37]

Bed horses on low-allergen materials like paper or cardboard, avoiding straw and dusty shavings. Avoid stalling horses under a hay loft, and remove them from the barn when hay is being moved or dropped for feeding. When feeding hay, avoid round bales, as they tend to be more contaminated with allergens like endotoxins, molds, and dust. Feed from a hay net or feeder so the horse cannot bury its nose into the hay, and consider wetting the hay before feeding — steaming or spraying may be enough, but soaking for longer is also fine.

[15:46]

For exercise, try to avoid having these horses breathe in dust and debris. Time rides when the arena has been watered or is less crowded. For barn-associated asthma, maximize riding outdoors and avoid poorly ventilated indoor arenas. For pasture-associated asthma, minimize outdoor exercise during allergy season, especially near or on pasture.

[16:21]

Now, dietary support: good nutrition ensures the horse is receiving the building blocks needed for overall health, immune function, and lung function. Start with a balanced vitamin and mineral intake as the foundation. We also recommend omega-3 supplementation, particularly EPA and DHA, which research has shown can help alleviate symptoms of equine asthma by providing anti-inflammatory support. Maintain asthmatic horses at an ideal body weight, as obesity in humans has been linked to worse disease control and increased reliance on medications — we assume the same is true for horses.

[17:24]

The last facet is medication. The two primary medications prescribed to asthmatic horses are steroids (powerful anti-inflammatories) and bronchodilators (which open constricted airways). For short-term use, these may be given orally. For severe or long-term cases, an inhaler may be recommended, delivering medication directly into the lungs after being nebulized or aerosolized into a fine mist. This method reduces the risk of systemic side effects and is especially helpful for horses that are poor candidates for systemic steroids.

[18:40]

Inhalers and nebulizers can be expensive and require training to acclimate the horse to the sounds and sensation, but they can be very effective for long-term management and are worth considering for severe cases.

[19:15]

Here are the references for today. Thanks so much for listening! Don’t forget to like and subscribe, and explore the other videos on our channel — we have new content coming out all the time. Check the description below for supplemental materials with more information about asthma and other respiratory diseases, as well as articles on nebulizer use and strategies to improve barn air quality. Until next time!