Heaves, Chronic Obstructive Pulmonary Disease, Recurrent Airway Obstruction, Equine Asthma
Heaves is a common term used to describe allergic respiratory disease of mature to older horses. It is characterized by increased breathing efforts at rest and chronic coughing. Originally described over 40 years ago by German veterinarian H. Sasse, COPD was his term to describe horses with breathing difficulties similar to humans. Our research now demonstrates that horse COPD is more similar to human asthma conditions. Veterinarians prefer to use the term ROA rather than Heaves or COPD to describe the respiratory condition in horses because RAO implies the reversible nature of the disease once horses are turned out on grass pasture. Equine asthma is used to describe the state of airway hyperresponsiveness following inhalation of dust particle commonly found in barns. Such exposure is usually the result of feeding moldy hay. However, some horses will present identical signs while being on pasture during the summer in response to high levels of grass molds and tree pollen.
Often, feeding round bales at pasture is more likely to trigger equine asthma and is usually associated with more severe disease. The difference between moldy hay and good quality hay is that both hays have mold; however, moldy hay has higher numbers of mold. A genetic predisposition has also been shown in some breeds, such as Warmblood and Lipizzaner.
The goals of therapy are to avoid exposure to dust and to treat lung irritation. The more effective method to avoid dust is by keeping asthmatic horse outdoors all of the time and not feeding hay. Instead, grass, pelleted feeds or hay cubes may be used as a hay substitute. Horses that must be housed in a barn, should be given low-dust bedding and feed. Any level of dust, even low-level dust, may trigger an asthmatic attack in horses. Soaking hay or steaming hay will help reduce the dust level. Most horses will improve 1-2 weeks after being turned out to pasture with no access to hay but it may take 1-2 months for horses kept indoors to show the benefits from reduced dust levels. Horses that only improve partially after dust exposure has been reduced should benefit further from drug treatment.
Lung irritation may be reduced by treatment with corticosteroids and bronchodilators. Albuterol is effective if given through aerosol, but it may only last one hour. It is reported to be poorly absorbed if ingested. Clenbuterol in liquid form is effective but expensive. Antihistamines may help some asthmatic horses but many horses will become tolerant of the medication over time. Recently, Purdue University College of Veterinary Medicine discovered that horses with asthma that were fed a supplement rich in omega-3 fatty acids allowed horses to breathe better and stop coughing within two to four weeks.
TAKE HOME MESSAGE FOR HORSES SUSPECTED OF HAVING RAO/ASTHMA/HEAVES
First, you must reduce your horse’s level of dust. Limit his/her time in the barn and keep your horse outside as much as possible. Soak not wet or sprinkle water on the hay. Feed low dust grain or hay substitute. Avoid round bale feeding. Add Omega-3 Fatty Acids to your horse’s diet. Finally, call the veterinarian and have your horse examined. An accurate diagnosis of RAO and asthma must be established since there may be other equine respiratory diseases that exhibit similar symptoms of Heaves. Finally, veterinarians can prescribe proper medications to alleviate your horse’s asthmatic symptoms and improve his quality of life.
excerpts for this article were copied in part from Equine Disease Quarterly Newsletter Dept of Vet Science Gluck Research Center – U of KY Lexington, KY 40546-0099 Jan 2015 vol 24, No 1