Equine asthma can affect horses of any age, breed, or discipline, making it harder for them to breathe properly and limiting their performance. The FDA has approved treatments such as inhaled ciclesonide for treating severe equine asthma, but these drugs’ efficacy in moderate cases is less clear.

Macarena Sanz, DVM, PhD, Dipl. ACVIM-LA, now an associate professor of equine medicine at Iowa State University, in Ames, along with her collaborators examined the potential benefits of inhaled ciclesonide for moderate equine asthma. The study, conducted while Sanz was at Washington State University (WSU), in Pullman, involved researchers from WSU, other Washington clinicians, and the University of Calgary, in Canada. Sanz and the team shared their findings in the Proceedings for the 2024 American Association of Equine Practitioners Convention, held Dec. 7-11, in Orlando, Florida.

Studying Ciclesonide in Horses With Asthma

Sanz and the research team studied 21 young racehorses confirmed to have moderate asthma over 10 days. They split the horses into two groups—one treated via an inhaler system with ciclesonide (12 horses) and a placebo group that use the inhaler without ciclesonide (9 horses). They blinded the researchers, trainers, owners, and grooms to the treatments.

The researchers performed a tracheal endoscopy on Day 0 and Day 10 and scored the  mucous present, bronchoalveolar lavage (BALF) cytology (looking at the cells under a microscope), and polymerase chain reaction (PCR) testing of BALF cell cytokines (cell-signaling proteins). They also asked the owners, trainers, and grooms to assess and score the horses’ respiratory signs daily.

In the horses treated with ciclesonide, the researchers noted improvement in the percentage of inflammatory cells and cytokines in the BAL F on Day 10. The owners, trainers, and grooms also noted a daily improvement in these horses’ clinical signs. “The treatment improved clinical signs, cough in particular, and decreased the percentage of mast cells in their bronchoalveolar lavage fluid, consistent with less inflammation,” said Sanz.

Clinical Applications and Future Ciclesonide Research

“We showed that treatment with inhaled ciclesonide can benefit young racehorses with moderate asthma,” said Sanz. Based on the team’s findings and because the inhaler system used in the study has been discontinued, Sanz said she and her fellow researchers believe veterinarians and researchers should evaluate the efficacy of ciclesonide administered through other available nebulizer systems.

“We showed a positive effect in young racehorses, but our study did not evaluate the duration of this response after the treatment discontinued,” said Sanz. She suggested following these horses for a longer period of time in future studies to evaluate the long-term efficacy of the drug.