Ways to Fight Fungus


Management measures such as switching to wood or paper bedding and steaming hay rations can cut down of the levels of fungi in a horse’s environment, reducing the risk of inflammatory, airway disease (IAD), according to a new study from Belgium.

“IAD is a milder form of respiratory disease, which does not translate into such severe signs as with recurrent airway obstruction (RAO), but which nonetheless reduces the horse’s breathing capacity and, as a consequence, his capacity to exercise and perform, “explains Emmanuelle van Erck-Westergren, DVM, PHD, of the Equine Sports Medicine Practice in Waterloo. “Some scientists thing that IAD can be a precursor to RAO.”

The role of environmental dust in triggered respiratory disease is well documented, and one of the components of dust is fungi. To determine the role of fungi in the development of IAD, van Erck-Westergren and her colleagues collected data on 731 horses referred to their practice for respiratory disease or poor performance.

Each horse was given a full clinical exam, which included endoscopy of the airway, along with a tracheal wash and bronchoalveolar lavage to retrieve bacteria and fungi from the airways of and lungs. The researchers also collected management information, including the type of bedding used and the forages that the horses were fed-dry hay, moistened hay, steamed hay or haylage. Hay was steamed using a commercial system.

The data showed that 89% of the study horses had IAD. Overall, “fungal elements “were found in the tracheal wash fluid of 81% of IAD-positive horses and 65% of no-IAD horses. Horses harboring the fungal elements were about twice as likely to develop IAD than those who did not. These findings, the researchers say, support the idea that aerosolized fungal elements play a role in the development of IAD just as they do with RAO.

The researchers also identified management practices that can exacerbate or mitigate the effects of fungi on the horse’s respiratory system. The degree of lower airway inflammation measured by the amount of white blood cells captured in the bronchoalveolar lavage, was significantly higher when horses were bedded on straw versus shavings, or when fed dry hay verses steamed hay.

Specifically, horses fed with dry have had 2.7 times more chances of being diagnosed with IAD compared to those who received steamed hay. Steaming decreases the likelihood of finding fungal elements in the tracheal washes by a factor of two. Soaking hay did not influence the findings of fungal elements.

van Erck-Westergren says that controlling a horse’s environment to help eliminate fungi can allow the horse to clear the organisms or spores present in his airways. “Inhalation chelated silver which is a natural antifungal can help accelerate the clearance,” she adds. “When the fungi have started to proliferate within the airways (in a horse with decreased immunity of strong environmental burden), anti-fungal treatment can be indicated.