What to Do When Your Horse is Exposed to Heavy Smoke
by R. Paul Schwab, DVM
Last summer was devastating for much of the west because of forest fires. Not only did the fires destroy acres of forest, farmland, and homes but they also impaired air quality hundreds of miles away which affected every breathing creature. Humans have the option of wearing facemasks and going inside to filter impure air; horses don’t have this luxury.
A horse’s respiratory system is designed to handle most of what the environment throws at it. The lungs are protected by a long defense system starting with the nose. The inside of the nasal cavity is filled with a labyrinth of mucosa covered thin bones that filter air as the horse inhales. Allergens and particles are mostly removed before they enter the lower airway. The trachea (windpipe) also has an elaborate defense mechanism; it is coated with mucus that traps particles which are then pushed back up toward the throat by tiny hair-like cilia that line its walls. The horse can then cough up the mucus with the trapped material. Any pathogens that make it down into the lungs are hopefully destroyed by white blood cells.
This system works incredibly well for the majority of horses. Just think about what a horse deals with everyday: dry hay, dusty areas, closed in trailers, dirty stalls, and long weekends at fairgrounds and rodeos. It’s when these defenses are overwhelmed that problems begin. For any disease there is the balance of an individual animal’s health/immune system, the environment that the animal lives in, and the amount of exposure to a pathogen or allergen. When this balance is tipped in one particular direction disease results. For example, a healthy horse in a dusty trailer on a long trip across the country is more likely to get respiratory issues like shipping fever because of the poor environment and stress of the long journey. The environment and health status of the horse is changed so that the balance favors the disease or pathogen.
Smoke inhalation is no different. The smoke is an inhaled toxin to the horse’s immune system. It can handle some smoke for a certain amount of time. Healthy horses with a good immune system and clean environment will likely do better than those with pre-existing issues. Horses that will be particularly sensitive to the effects of poor air quality from smoke will be those that have Equine Recurrent Airway Obstruction (this is what we used to call COPD or “heaves”). These horses are very sensitive to poor air quality and will need to be monitored closely. Young horses and geriatric horses may be more sensitive as well because of the developing and the waning immune system, respectively.
Clinical signs of chronic smoke inhalation are similar to any other respiratory problem. Horses may have coughing, increased respiratory rate, labored breathing, depression, and/or fever. Cases after acute heavy exposure can have severe airway fluid build-up and thermal damage to the lining of the respiratory tract. Some of the more serious cases can develop secondary pneumonia days later. Treatment of smoke inhalation is directed and providing clean air and supplemental oxygen if practical. Drugs to decrease the inflammation are used as well as bronchodilators to help open up the airways so the horse can move air easier. If treatment is initiated early, and damage to the lungs is minimal, prognosis is good.
Because we can’t control the outside air until the smoke subsides, prevention of disease involves keeping this balance of environment/animal/pathogen in check. Unless you have a barn with an elaborate air filtration system, the air quality inside is probably still worse than outside. Smoke in the air outside is probably better than smoke + hay + ammonia + sawdust + poor air flow on the inside. If the horse is stabled inside pay extra attention to keeping the environment clean and dust-free. Consider wetting down the bedding and hay. On days when the air quality is particularly bad you should avoid working your horse so that it isn’t taking frequent deep breaths. People who have horses in narrow valleys that tend to hold more smoke may consider moving their horses to other locations.
Finally, healthy horses tend to fight disease better than unhealthy horses. Good nutrition, parasite control, and other preventive measures will help to insure that your horse can handle whatever Mother Nature throws at it.
Published November 2012