Respiratory Diseases

Exercise Induced Pulmonary Hemorrhage (EIPH)

A 'bleeder' is a horse that has shown signs of bleeding from the lungs after exercise. Some horses may have blood that comes out of the nostrils (called epistaxis), but most will not. This condition is known as Exercise Induced Pulmonary Hemorrhage (EIPH), and is most commonly diagnosed by the presence of blood in the airways after exercise using an endoscope or a bronchoalveolar lavage. 

EIPH is not yet fully understood, but currently the most widely accepted theory is that during exercise, blood pressure in the lungs can increase to such a high level that small capillaries burst, and blood ends up in the lungs. Approximately half an hour after strenuous exercise, this blood can usually then be seen in the trachea (windpipe). 

We do not yet know why it happens, but in some cases it may be influenced by lung inflammation and in others by obstruction to airflow in the throat. The obstructions in the throat area can happen sometimes only during exercise or be permanent (for example ‘roarers”). In horses that do not show signs of lung inflammation nor throat obstruction or cardiac problems, it is unclear why EIPH occurs. 

Only about 5% of horses with EIPH will have blood that comes out of the nostrils. Therefore, there may be many horses that have EIPH without an owner knowing.

There are two common ways to diagnose EIPH: 

  1. Endoscopy of the trachea (windpipe) 30 minutes after exercise: An endoscopy uses a long tube with a camera on the end that goes into the horse's nostril, looks into the back of the throat and down the wind pipe (trachea). It is a very quick procedure that most horses tolerate well, and does not require sedation to be performed. The trachea is visibly assessed to see if blood is present. The endoscopy should be performed between 30 and 60 minutes after strenuous exercise. 
  2. Bronchoalveolar lavage (BAL): A bronchoalveolar lavage is more invasive and is performed under sedation. The endoscope is very long (3 meters) and goes much deeper into the lungs where it then flushes sterile fluid (same as for IV fluids) in. This fluid is collected and analyzed microscopically to see if any red blood cells are present, which can indicate bleeding in that area of the lung. 

In addition to be a health (and potentially welfare/ public perception) issue, EIPH is a performance limiting disease, so some horses may show poor performance. EIPH has been more closely studied in racehorses in Australia, where several studies found that those racehorses with EIPH were slower and finished significantly further behind the winning horse than horses that did not have EIPH. 

Some owners have also reported other signs such as coughing or behavioral changes, but there are many horses with EIPH that show no clinical signs at all. Each horse is different, and clinical signs can also vary with the severity of the disease. 

There is currently no cure for EIPH, but there are some prevention treatment options to help reduce the severity and incidence. 

Furosemide (Lasix): This drug is a diuretic, meaning it acts on the kidneys to increase urine production and urination. This dehydrates the horse and the goal is to decrease blood pressure. The decrease in blood pressure is due to the decrease in blood volume. Lasix is somewhat controversial, as horses may lose a significant amount of electrolytes and are also not supposed to drink any water for several hours before their race. Some horses respond well and will show a decrease in the severity of EIPH while using Lasix, but some horses will not respond to the drug at all. 

Nasal Strips: Nasal strips may help some horses that have a low severity of EIPH. Nasal strips work to increase the amount of air flow through the nostrils by a small percentage. There is weak evidence showing that they will help horses with EIPH.  

Bronchodilators (Ventipulmin, Clenbuterol): Bronchodilators work by dilating the smallest airways in the lungs, which decreases resistance and increases air flow. There is very little evidence to show that they are an effective treatment for EIPH.

Corticosteroids (Dexamethasone): Corticosteroids are anti-inflammatories. These may help if the horse shows signs of lung inflammation. During the inflammation response there is increased blood flow to the inflamed area with new, weaker blood vessels being formed. During exercise these blood vessels rupture more easily than existing blood vessels which may lead to an increase in blood seen in the trachea. 

By conducting studies, we are trying to quantify the prevalence of EIPH in barrel racing horses and also continue to raise awareness about what it is and what effects it may have on a horse's health. 

At the end of the summer we will be conducting a further study for horses that have been diagnosed with EIPH. This study will test a new drug that has been shown effective to prevent EIPH in racehorses. It is an exciting drug that acts only on the lungs and has shown no adverse side effects, making it much more attractive than other drugs currently being used to treat EIPH. More information will be sent out later this summer to those owners with horses that have been diagnosed with EIPH. 


Inflammatory Airway Disease

Inflammatory Airway Disease (IAD) is a non-infectious disease of the lower respiratory tract. IAD is triggered by dust, allergens or other endotoxins that cause an immune response when inhaled. Typically, horses with IAD have no clinical signs at rest however respiratory signs will be noticed during exercise. Horses may exhibit any or all of the following: exercise intolerance, cough, increased respiratory secretions and mucus. IAD is a non-septic disease, therefore fever and other signs of infection are absent.  

Horses exposed to high levels of environmental dust, organic molds and other endotoxins appear to be the most susceptible to developing IAD. There may also be a genetic component as some horses are more susceptible to bacteria, viruses and other inhaled environmental pollutants than others.  Horses usually have no history specific to IAD and it can affect them at any age.

Horses develop an immune response that shows up as an inflammation of the lungs and can have a mucous blockage of the bronchioles. Horses kept inside on straw beddings are exposed to larger amounts of dust than those bedded on wood shavings or kept on pasture, as are those who are fed hay rather than pelleted feed.

The effect of IAD on performance depends on the severity of the disease and the level of exertion. If a horse is not removed from the environment or treated properly, IAD may have an adverse effect on performance, however unless there is severe airflow obstruction or persistent coughing, IAD is less likely to cause exercise intolerance in horses working at lower intensities.

The ACVIM Consensus Paper (2007) states that to confirm a diagnosis of IAD horses must have no evidence of systemic signs of infection (fever) and they must not exhibit any respiratory clinical signs at rest. During exercise they will have at least one of the following: poor performance, exercise intolerance, or coughing, with or without excess tracheal mucus. They must also show evidence of lower airway inflammation.

Bronchoalveolar lavage fluid (BAL) cytology is the most common tool used to assess inflammation and sample cells of the lower airway. Horses are given a sedative and an endoscope or a small tube is passed through the nostrils into the lower airway until it wedges into a small bronchus in the lung. Saline solution is washed over the lung tissue and cells are recovered by aspirating the fluid from the airways.  To confirm a diagnosis of IAD the sample must have an elevated number of neutraphils (>5%) and/or mast cells (>2%) and/or eosinophils (>0.1%).

Watch Video: A trip inside a horse's lung

Pulmonary function and airway hyper-responsiveness tests may also be used for research diagnostic purposes however they are not practical for use in the field. Another simple way to determine whether or not a horse has IAD is to perform the hay challenge, in which moldy hay is shook over the horses nose. Horses with IAD will not be affected and will therefore test negatively. If clinical signs are manifested following the hay challenge (testing positively) horses may have recurrent airway obstruction (RAO).

IAD is best avoided by decreasing environmental dust (see below).

Medical therapy usually focuses on the use of corticosteroids and bronchodilators to effectively control airway inflammation and relieve airflow obstruction. Bronchodilators should only be used when the air quality of the environment is good. Non-steroidal anti-inflammatory drugs (NSAIDS) and antihistamine drugs are ineffective for IAD. Horses with IAD generally have a good prognosis for returning to previous levels of activity and performance when medical therapy is prescribed and environmental changes are made.

Read more about Dr. Léguillette's research on IAD here.


Recurrent Airway Disease (RAO)

Recurrent airway obstruction (also known as RAO or heaves) is a non-septic allergic respiratory disease causing severe airway inflammation and obstruction. Horses with RAO are affected when organic dusts are inhaled causing bronchospasm and mucus accumulation. It is comparable to asthma in people.

RAO is characterized by a chronic cough and abnormal breathing sounds, accumulation of mucus in the tracheobroncial tree, nasal discharge, dyspnea and exercise intolerance. To be diagnosed with RAO clinical signs and labored breathing must be present at rest. A horse experiencing an acute episode may also have an increased respiratory rate and an anxious and agitated appearance. There will also be an apparent use of its abdominal muscles to assist with expiration. Horses with chronic heaves will begin to display the characteristic heave line due to the hypertrophy of their external oblique muscles.

Watch Video: Horse with RAO

Horses that experience RAO are hypersensitive to inhaled organic molds and endotoxins. Genetics may contribute to a horse’s susceptibility of the disease. Clinical signs can be triggered sometimes in a matter of minutes when exposed to a dusty or moldy environment. Removing horses from the environment often helps reverse the clinical signs.

Exercise intolerance is dependent on the level of exertion and the severity of the disease however if the horse is not treated properly or removed from the environment, symptoms may increase until the horse is in severe respiratory distress. RAO is a chronic disease therefore the earlier RAO is recognized, diagnosed and treated, the better the outcome.

Horses with RAO will have recurrent or seasonal clinical signs that include labored breathing at rest. They may also have a cough and mucoid to purulent discharge. BAL cytology is important for diagnostic purposes and for monitoring the response to therapy. Horses with RAO present with marked neutraphils (>20%) and will test positive to the moldy hay challenge.

Medical therapy consisting of corticosteroids and bronchodilators is used to control the inflammation of the airways and relieve airway obstruction by relaxing the smooth muscle. Medical therapy will help most horses become free of clinical symptoms however medication alone will not reverse the effects; life-long environmental changes are also necessary for successful management the disease. Exposure to allergens often results in flare-ups therefore its very important that horses with RAO are kept in low dust environments.

Aerosol medication is best delivered to horses using an Aerohippus Aerosol Chamber. For more information you can visit their website here.

Watch Video: Using the Equine AeroHippus

FEED

  • Round bales: Avoid self-feeding round bales as these contain a lot more dust and horses are more likely to bury their heads and breath in dust particles and possibly mold spores as they eat. If horses are being fed from a round bale, break it apart and spread it out. Try to feed only as much as they need at one time.
  • Hay Flakes: Microscopic molds cannot be seen however can often be smelled. Open up hay flakes and smell them before you feed them. Do not feed hay that smells or appears moldy.
  • Soaking hay: Some horses may need to have their hay soaked before eating it. Soaking for 15 to 20 minutes is considered best practice however this is not always ideal or practical, especially during winter months. Hay steamers are a great solution and more information can be found at www.happyhorseproducts.ca.
  • Pelleted feed: Consider switching to hay cubes mixed with alfalfa pellets

BEDDING

  • Avoid straw bedding, sawdust and other fine wood shavings, as these are very high in dust. Mold grows easily in straw and are invisible to the eye. Coarser wood shavings, cardboard or paper shavings are preferred.

OTHER

  • Ventilation: Proper ventilation is essential for removal of airbone particles.
  • Turnout: Keep horses outside on pasture as much as you can as the expsosure to dust is dramatically lower outside than in the stable. Be mindful of outdoor dust, especially if you are close to a gravel road or during crop harvesting times.
  • Cleaning: Avoid mucking, sweeping and completing other barn chores (dusting, cobwebs, moving hay/straw) while horses are in the barn. This is when dust particles in the air are at the highest. Hosing down alley ways before sweeping will help keep dust from rising.

Read more about RAO here (PDF article by Dr. Léguillette).

If you think your horse may have IAD or RAO check out: the BAL Consulation page for more information.