Does Treating Equine Asthma Help Soft Palate Problems?

Researchers recently reported that dorsal displacement of the soft palate (DDSP) in horses could be a result of asthma.^* Testing and treating horses for asthma rather than focusing on the soft palate exclusively, particularly in cases of poor performance, could serve as a reasonable alternative to surgery.

Current treatment recommendations for asthma include: (1) limiting the horse’s exposure to aeroallergens by maximizing turnout and minimizing time in a stall; (2) administering appropriate medications such as bronchodilators and corticosteroid anti-inflammatory drugs; and (3) offering a high-quality marine-derived omega-3 supplement.

“Together, these management strategies can reduce inflammation, bronchospasm, and mucus accumulation in the lower airways in horses with asthma,” explained Catherine Whitehouse, M.S., a Kentucky Equine Research advisor. These same clinical signs are believed by researchers to contribute to upper airway alterations, such as DDSP, possibly by increasing the negative pressure in the nasopharynx.

This link between asthma and DDSP was demonstrated using 57 horses with a history of asthma actively competing at the national level. All horses included in the study underwent resting endoscopy in which a small fiberoptic camera was passed through the horse’s nostril and nasopharynx into the trachea. Samples of mucus and inflammatory cells were collected during routine tracheal and bronchoalveolar washes. Horses with severe asthma and evidence of DDSP on resting endoscopy were also evaluated using overground endoscopy (performed while exercising). Four horses were removed from the study, leaving 53 horses for data analysis.

“In total, 42% of the horses were diagnosed with mild to moderate asthma, and 58% horses were diagnosed with severe asthma. These horses were competing at high levels, showing that their asthma could be managed sufficiently to maintain performance,” Whitehouse noted.

In total, 82% of the horses with mild or moderate asthma and 94% of the horses with severe asthma had DDSP. Further, all of the horses with severe asthma evaluated via overground endoscopy had DDSP.

The theory that asthma results in DDSP contradicts previous thoughts on DDSP. Usually, DDSP is attributable to respiratory infections, structural abnormalities (e.g., epiglottic cysts or chondritis), or muscle weakness of the laryngeal or surrounding muscles, most notably the thyrohyoid muscle. In this study, each of these potential causes was ruled out, making asthma a reasonable cause for the observed DDSP. As such, surgery may not be indicated for all, and perhaps many, cases of DDSP.

“This study highlights the importance of airway management, which can include dietary alterations to minimize feeding dry hay, dust control in both housing and riding areas, and increasing the amount of anti-inflammatory omega-3 fatty acids fed,” advised Whitehouse. “EO-3, is a palatable, potent marine-derived oil rich in omega-3 fatty acids that is easily top-dressed on feed.”

^*Joó, K., Á. Povázsai, Z. Nyerges-Bohák, O. Szenci, and O. Kutasi. 2021. Asthmatic disease as an underlying cause of dorsal displacement of the soft palate in horses. Journal of Equine Veterinary Science 96:103308.