In this episode of the Disease Du Jour podcast, Beau Whitaker, DVM, CERP, joined us to discuss equine asthma and exercise-induced pulmonary hemorrhage (EIPH), including clinical signs, risk factors, and treatment and management options.
What Is Equine Asthma?
Whitaker described the two main categories of equine asthma:
- Severe equine asthma, also known as heaves, is the more serious form, where horses exhibit clear breathing difficulties at rest, including labored breathing, flaring nostrils, rib cage movement, and sometimes audible respiratory sounds. This condition is caused by a strong immune response to environmental dust, mold, or other airborne irritants, leading to bronchoconstriction. In extreme cases, it can be life-threatening.
- Mild to moderate equine asthma is the less severe form. Horses often appear normal at rest but might show signs of respiratory distress during exercise, such as coughing, difficulty recovering after exertion, or becoming winded more quickly than usual. These horses experience less bronchoconstriction and mucus production.
“They’re almost different diseases in some ways,” said Whitaker.
Risk Factors for Equine Asthma
Whitaker explained two main triggers for equine asthma: summer pasture and dusty barns. Where he practices in Texas, he sees more cases in the spring and summer. In colder climates, cases might be more prevalent in the winter when horses spend more time indoors. Round bales are another risk factor, as they usually contain a lot of dust.
Whitaker said equine asthma is especially common in barrel horses, likely because these horses stir up so much dust while they’re running and breathing hard. They also spend a lot of time in the trailer traveling to rodeos, which increases their dust exposure.
Diagnosing Equine Asthma
Whitaker said severe equine asthma is usually obvious; these horses are visibly struggling to breathe and displaying exaggerated rib cage movement. He said it’s important to rule out infectious causes like pneumonia, but advanced diagnostic procedures aren’t usually necessary.
For mild to moderate equine asthma, Whitaker typically starts with endoscopy of the upper airway. “There’s a high correlation between mild to moderate asthma and mucus in the trachea,” he said.
The most definitive way to diagnose the condition is via bronchoalveolar lavage (BAL), which involves injecting sterile saline into the lungs, drawing it back out, and performing cytology to analyze the types of cells present. Whitaker said performing a BAL is helpful even if you already know the horse has asthma because it can help you target your treatment more effectively based on the causative cell types.
Treatment and Management Strategies for Equine Asthma
Whitaker said the first step in managing equine asthma is assessing the horse’s feed and environment, “because that’s probably where you can make the largest improvement.” Round bales should be removed. Wetting or steaming the hay is often beneficial. Owners should also take steps to minimize dust in the horse’s grain. Whitaker said marine-derived omega-3 fatty acid supplements have been shown to be effective in some studies.
Medical therapies will depend on the asthma’s severity. Whitaker said corticosteroid therapy will likely be most effective, at least initially. If horses are going to require ongoing maintenance, Whitaker encourages clients to get a nebulizer so they can direct treatment into the lungs. Often, he puts a bronchodilator in the nebulizer to help open the airways. Sometimes, he uses a combination of a corticosteroid or bronchodilator and a mast cell stabilizer.
More recently, some effective nonpharmaceutical treatments have emerged, including inhaled orthobiologics. Whitaker sometimes uses a combination of regenerative and pharmaceutical therapies. Over the past couple of years, he has been researching shock wave therapy for horses’ lungs, which has also been shown to be effective in treating asthma.
Equine Asthma Prognosis
Whitaker said horses with severe equine asthma usually need to retire from performance careers, although some might be able to continue in light work. Horses with mild to moderate asthma can typically continue performing at a high level with the right management practices.
What Is EIPH?
Exercise-induced pulmonary hemorrhage (EIPH) is a condition where blood enters the lungs during intense exercise due to high cardiovascular and respiratory pressures. It primarily affects racehorses and other performance horses that exert themselves at high speeds.
EIPH occurs due to the extreme pressures generated in a horse’s body during intense exercise. When a horse runs, it breathes in large amounts of air (about four gallons per second), and its heart beats at an extremely high rate (around four beats per second). This creates a push-and-pull effect on the delicate alveoli in the lungs, creating fissures and allowing blood to enter the lungs.
Whitaker said asthma can contribute to EIPH and make the condition worse, but EIPH does not appear to contribute to asthma.
Clinical Signs of EIPH
The most common clinical sign of EIPH is epistaxis, but most horses with the condition don’t bleed from the nose. Whitaker commonly sees the condition in barrel horses. He said these horses often display subtle clinical signs, such as pulling up after running the third barrel, coughing at the end of the run, or becoming apprehensive about entering the arena. “That’s a common symptom we see, is the horses starting to refuse to go in the alleyway because they’re expecting that bleeding, and they don’t want to go run because it’s uncomfortable to them,” he said.
Diagnosing EIPH
Diagnosing EIPH might involve scoping the trachea within a day of the horse’s run. Blood in the trachea is diagnostic, but Whitaker said a good percentage of horses don’t bleed into the trachea and only have blood in the lungs.
“A study was performed where they scoped the horses and did BALs, and the BALs were a much more sensitive diagnostic tool for diagnosing EIPH,” said Whitaker. He said you will know immediately upon performing the BAL if the horse has EIPH because the saline will be red when you pull it back out of the lungs.
Treatment and Management Strategies for EIPH
Whitaker said furosemide is the most common treatment for EIPH, which might not be legal depending on the sport. Nasal flare strips can also be effective in opening the airways and decreasing EIPH. There are some other products on the market that owners often use, but “the only two things that have really been shown to be effective from a research standpoint are furosemide and the nasal strips,” he said.
The condition is progressive; each time the horse bleeds it creates fibrosis in the lungs. Therefore, some horses with EIPH must retire from high-exertion careers. However, Whitaker has had some success in managing horses that have both EIPH and asthma. “They’re about to retire and we treated their asthma, and they were able to continue,” he said, noting the horses without asthma are more difficult to treat.
About Dr. Beau Whitaker
Beau Whitaker, DVM, CERP, is a partner at Brazos Valley Equine Hospital, in Salado, Texas. He was raised on a family farm in Tennessee before acquiring a B.S. in Animal Science from Oklahoma State University. After a gap year spent training horses, he attended and graduated from Texas A&M University College of Veterinary Medicine in 2005. Upon graduation, he completed an internship at Arizona Equine Hospital and then worked as a veterinarian at the 6666 Ranch in Guthrie, Texas, before moving to Salado, where he has practiced since 2007. Whitaker is a Certified Equine Rehabilitation Practitioner and focuses his work in the areas of sports medicine, regenerative therapies, and clinical research. He has participated in multiple clinical research trials for equine therapeutics and performs equine product development research. He regularly speaks at conferences and contributes to publications. In 2022, he was named the AAEP Good Hands Veterinarian of the Year and PATH International Veterinarian of the Year for his work with therapeutic riding centers.
Related Reading
- Managing Severe Equine Asthma
- Impacts of Wildfire Smoke Exposure on Horses’ Lower Airways
- Electrical Impedance Tomography: A Promising Imaging Modality
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