Effective breathing is important for sporthorses to be at their best, but equine asthma can hinder horses’ performance in the show ring and affect their quality of life. “Equine asthma is a chronic respiratory disease in adult horses,” says Cricket Russillo, DVM, of High Performance Equine based in northern Virginia and Wellington, Florida. Studies have found that mild to moderate forms of equine asthma, known as inflammatory airway disease, may affect 68-80% of horses. Additionally, 14-17% of horses may be affected by the severe form of the disease, referred to as recurrent airway disease or heaves.

An Overview of Equine Asthma

With equine asthma, there is chain reaction in the airways due to an inflammatory response. When a horse is affected by the disease, Russillo explains that allergens trigger inflammatory cells to infiltrate the lungs and release different proteins and signaling molecules, such as proteases and cytokines. She adds that proteases are enzymes that break down proteins, causing damage to tissues, while cytokines are molecules that communicate cell to cell, furthering the inflammatory response.

“Those products end up leading downstream effects that increases the inflammation and damage to both the airway and the lung and result in the clinical signs,” Russillo says. “If you think of a dish sponge, the lungs are kind of spongy. There is lots of surface area there that is meant to allow optimum oxygen exchange across the airway for absorption. When you get thickening because of inflammation or excess mucus, that makes that oxygen exchange much, much harder.”

Clinical Signs of Equine Asthma

Clinical signs of equine asthma include:

• mild to severe coughing,
• nasal discharge,
• increased respiratory effort (increased respiratory rate and/or noticeable use of abdominal muscles at rest),
• and decreased performance/exercise intolerance.

Russillo regularly sees equine asthma affecting sporthorses, noting that is common across the United States and not specific to a certain region. “When you look at poor performance, it’s musculoskeletal problems and then it’s asthma,” she says. “Respiratory disease is going to be the number two reason why we have performance loss.”

Genetics and environmental allergens, such as dust, fungi and mold, may contribute to the development of the disease. Russillo finds that some horses are more affected by the disease at certain times of the year. “Some horses are more affected in the wintertime because we lose ventilation, the barn doors get closed, the windows get closed and there’s increased allergens in the environment,” she says. “And some horses are worse during the summer because they’re more stimulated by the pollens and the allergens that are in the air at that time.”

Treating Equine Asthma

Equine asthma treatment focuses on decreasing and controlling airway inflammation. Russillo explains that treatment plans are multimodal, meaning more than one drug or more than one change are implemented to effectively manage the disease. She notes that management and environmental changes are a key part of any treatment plan. Russillo says that management changes can include wetting, soaking or steaming hay; not feeding round bales; and increasing ventilation by moving the affected horse to an end stall or using a fan during the summer months. Also, a study found that switching to a low-dust feed and supplementing the diet with omega-3 fatty acids decreased clinical signs of the disease versus switching only to a low-dust feed. Russillo notes that marine-sourced omega-3 fatty acids are more beneficial than vegetable-sourced omega-3 fatty acids for horses with equine asthma.

The other portion of the equine asthma treatment plan is pharmaceutical management. Corticosteroids are common treatments for the disease, and they are administered systemically (affecting the body as a whole) or inhaled. Horses are able to inhale corticosteroids using an aerosol chamber inhaler (similar to a human inhaler) or a nebulizer. Russillo notes that corticosteroids are effective at suppressing inflammation but not tolerated well by all horses.

Bronchodilators are another drug commonly used to treat equine asthma. Russillo explains bronchodilators open the airways thus reducing coughing and helping clear excess mucus. She adds these drugs are often prescribed with corticosteroids, creating a “one-two punch” with treating the disease. Other drug treatment options are mast cell stabilizers, which decrease airway inflammation, and mucolytics, which break down mucus. While several treatment options exist, researchers are continually looking for ways to improve the quality of life for horses affected with the disease.

An Innovative Treatment Option

A molecule called alpha-2 macroglobulin, an orthobiologic normally used for managing orthopedic conditions, has been looked at for its ability to help manage equine asthma. An orthobiologic is a substance found naturally in the body, that, when used in higher concentrations than are typically found in the blood, may help speed the healing process. When delivered with a nebulizer, α2M has demonstrated benefits for horses with asthma in a preliminary study. The promising nature of this study led to a pilot study further exploring α2M as an equine asthma treatment option.

In the pilot study, horses received six nebulizer treatments of Alpha2EQ®, an α2M product developed by Astaria Global, at 48-hour intervals. Thirty of the 34 horses, or 88.2%, had successful results in the pilot study. Horses showed improvement beyond the study timeframe, with up to six months of decreased clinical signs of equine asthma. Additionally, horses who showed a return of clinical signs of the disease were maintained with one nebulization once every four weeks.

A Larger Study

The positive results led to a larger study that began January 2024 to take a further look at the benefits of α2M. Dan Dreyfuss, DVM, MA, summarized the work to this point by saying, “As with all initial studies there are limitations to these pilot studies, but we are very encouraged by the results, and the results from hundreds of subsequent horses nebulized with α2M. The hope is that this product will provide veterinarians with a new means of managing equine asthma—a non-corticosteroid anti-inflammatory option.”

Russillo sees Alpha2EQ® as an intriguing equine asthma treatment option. “[Alpha-2 macroglobulin] is an immune modulator, cytokine inhibitor, protease inhibitor. When you suspend it through the nebulization process and deliver it down into the lung tissue, it then acts in that environment to do all those things that reduces the inflammation,” she says. “So far, the effects that we’re seeing in the pilot studies have shown that it’s very well tolerated. There are not side effects from using it [via nebulization], and it seems to be really effective for controlling equine asthma.”

This article is brought to you by Astaria Global.