Equine Asthma
What is Equine Asthma?
Over the years, Equine Asthma has had many names, including respiratory allergies, Heaves, Chronic Obstructive Pulmonary Disease (COPD) and Inflammatory Airway Disease (IAD). In the latest consensus, researchers have decided that Equine Asthma is the best terminology to describe the condition of chronic respiratory inflammation, and then qualify it as mild or severe depending on the signs observed and test results. Regardless of the name it is given, Equine Asthma is inflammation of the bronchi and air sacs (alveoli) of the lungs causing restrictive breathing, coughing and exercise intolerance or poor performance.
The condition is believed to be triggered by dust, pollen, fungi or other allergens which start an inflammatory cascade in the lungs. Left untreated, the airways swell and the air sacs can fill with fluid and debris, preventing the horse from breathing efficiently. In advanced cases, research has now confirmed scarring of the lungs, indicating an irreversible, chronic lung disease.
Although Equine Asthma is triggered by allergens and stabled horses are more at risk, allergens can also be present in paddocks leading to “pasture-associated” equine asthma.
What are the clinical signs of Equine Asthma?
Earliest signs of asthma typically occur when the horse is exerting himself, and is needing to breathe deeply. In racehorses, slower race times, longer recoveries and even bleeding from the lungs can be observed. Similarly, in other disciplines, the same exercise intolerance can be seen as poor performance, less energy, mistakes or tiring more easily. Coughing or mild clear nasal discharge may be seen at the beginning or end of work, especially in indoors or dusty arenas. At rest, horses may be heard to cough while eating from their hay, as they bury their nose or inhale the dust when hay is shaken.
As the condition progresses, coughing can be heard at rest, nostril flaring and even abdominal breathing will be noticed. These all indicate that the horse has maximized its respiratory effort, without the physical exertion that would warrant it. These cases are considered to be in respiratory distress, although they may “seem fine” otherwise. When difficulty breathing or coughing is noticed at rest, the asthma is considered to be severe.
How is Equine Asthma diagnosed?
Asthma is suspected based on clinical signs of increased respiratory effort or recovery from work, and coughing. A confirmation and severity assessment requires a lung wash (bronchoalveolar lavage, BAL), endoscopy, and sometimes blood work.
A bronchoalveolar lavage, or BAL, involves infusing a small amount of sterile saline into the lungs and collecting it back to see what kind of immune cells are in the area. The types of cells present may suggest how well the horse will respond to treatment or if an infectious component is present. The BAL will also identify excess mucus, bacteria, plant debris, and pollen.
Endoscopy is also recommended, especially in athletes who may have milder signs of asthma or concurrent mechanical issues such as a dorsal displacement of the soft palate which can contribute to poor performance. Endoscopy will assess the mucus content and quality, inflammation in the throat and trachea, and adds to the prognostication of asthma.
Routine blood analysis may be beneficial to determine if a secondary infection is complicating the respiratory condition observed, or if there are other ailments that may be contributing to the poor performance in your horse.
How do you treat or control Equine Asthma?
Just as environmental allergens generally cause the asthma, the environment must also be controlled in order to manage asthma. Medications are used to calm the airways but the inciting cause must be removed in order to truly “cure” the inflammation.
Environmental management involves reducing dust by turning horses out as much as possible, improving airflow in the barns, removing horses from barns during cleaning and bedding or feeding, or wetting down arenas or barns. A big source of dust and allergens comes from hay: baled hay tends to remain moist in the center allowing fungi to grow, and then aerosolize as the bale is broken open or as the horse buries his nose while he eats. For this reason, large round bales or oversized square bales should be avoided and loose hay is preferred. Although nibble nets may reduce wastage, horses may shake the net, dispersing large amounts of dust. If dusty hay cannot be avoided, wetting or steaming the hay reduces allergens significantly. In severe asthmatic cases, hay is avoided entirely in favor of soaked feeds and hay cubes.
Treatment for Equine Asthma is reliant on corticosteroids, either given orally or inhaled. However, without proper environmental management, response to corticosteroid will decline and the respiratory distress will progress. Treatments are started at a high dose to calm the immune system and then tapered down once clinical signs resolve. In chronic cases, repeating the BAL is recommended to monitor the response to therapy and guide future treatment.
In addition to corticosteroids, bronchodilators are used to help open the airways and improve breathing. These are symptomatic treatments only therefore are used during acute respiratory distress and not meant for long term daily treatment.
What supportive therapies are available to manage Equine Asthma?
Adjunctive treatments may reduce fibrosis and decrease inflammation, slowing progression of asthma.
A comprehensive nutritional assessment may detect sources of systemic inflammation due to excessive sugars, allergens in processed feeds or imbalances in Omega 3-6-9 ratios. Resolution of systemic inflammation is important for minimizing ongoing inflammation in the lung tissue and will help overall resolution of clinical symptoms. Nutritional assessment will also ensure that sufficient protein is available for ongoing repair processes too.
Supplements can aid in improving lung function and in supporting overall immune competency as well. Products such as Lung Flush followed by RespiFree® (Omega Alpha) once the initial medical treatment is completed as well as the addition of probiotics and herbal immune supports, including Immune Plus (Omega Alpha) may be indicated in some cases. Other anti-inflammatory supplements include Anti-Flam (Omega Alpha), turmeric, cayenne, Vitamin C, Vitamin E, and balanced sources of omega rich fatty acids supplements which may also be recommend in conjunction with other rehabilitation activities.
Manual therapies can support optimum mechanical functionality of the thoracic cavity, ensuring no restrictions associated with expanding the chest cavity, supporting optimal lymph and blood flow to the region. Chiropractic care or manual adjustments, cranial sacral therapy, massage, myofascial release, Laser and even kinesiology taping can all exert positive effects supporting lung health and the mechanics of breathing.
Exercises to build core and offering postural supports will further facilitate physical aspects of respiration and directed re-breathing exercises, for example, increase tidal volume and may decrease the formation of fibrosis.
How do you prevent Equine Asthma or is it genetic?
There does appear to be a parental influence on whether your horse will develop asthma, therefore horses with known parentage suffering from asthma should be managed more aggressively prior to the onset of clinical signs to prevent the progression or development of the disease.
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