oxygen flow to the body and therefore overall performance and quality of life. Invaders into the nasal passages that can trigger an inflammatory response include dust, mold spores, fungi, endotoxin from bacteria, cold air, exercise, stress, anxiety, mite debris, noxious gases such as ammonia from urine and other allergens including smoke-filled air, as Nevita experienced. Barn life can be a hotbed of asthma triggers. “Along the way, distinctions have been drawn between those horses that develop difficulty breathing at rest (heaves, RAO, severe equine asthma) and those that do not (IAD, mild equine asthma). While leading to confusion for the horse owner, the changing terminology actually reflects improve- ments in veterinary knowledge,” wrote Drs. Kathleen Ivester and Laurent Couetil of Purdue University College of Veteri- nary Medicine in an April blog for Haygain. “Respiratory diseases are a matter of progression and
degree,” says Dr. Chiapetta. Asthma appears as one of several respiratory disorders including inflammatory air disease (IAD), recurrent airways obstruction (RAO) and chronic obstructive pulmonary disease (COPD/heaves), usually occur- ring from an allergic reaction to inhaled particles. For example, with IAD, as described earlier, the airways
are thickened, narrowed and lined with mucus and white blood cells. Oxygen movement out of the lungs into the blood stream is reduced. Over time, the inflammatory fluid carries fibrinogen, the substance “that forms when you have a wound and helps with healing, but is also what forms into a scar,” explains Dr. Chiapetta. “With chronic airway disease, over time you get scar tissue forming in the lung. Everything else before the laying down of scar tissue is easier to heal. But if it continues for a long time and scarring develops, you have a chronic effect or COPD/RAO.” “Then the lungs aren’t as elastic and oxygen doesn’t
diffuse into the bloodstream as well. The pulmonary alveoli membrane between the alveoli and capillaries is very thin— 1/100th the thickness of human hair. Although fragile, it is also very efficient for movement of O2 and CO2. However, when you get a layer of scar tissue, inflammatory fluids and pus, the oxygen can’t jump onto the blood cells that carry the blood through the capillaries to oxygenate the body. When the oxygen uptake is blocked, the horse’s body has to work harder to take in air,” he continues. On a horse with COPD, you may see the heave line running obliquely down along the abdomen toward the back of the elbow since the horse has actually built up stron- ger abdominal muscles because of exerting greater effort to push air in and out. “Oftentimes, with the COPD horse, when pollen or virus goes away, horses may breathe easier for a while, but flare ups reoccur when re-exposed to an irritant and the horse will start breathing heavy again. Some horses with severe COPD may be constantly breathing heavy,” Dr. Chiapetta adds. COPD and RAO are most prevalent during high anti- gen times of the year, spring and summer, and less preva- lent during fall and winter. “Unfortunately, the condition is
recurrent and with each flare-up, it continues to damage the lung tissue,” says Dr. Tom Schell, veterinarian, founder of Nouvelle Research and author of Seeing the Whole Horse. “In my opinion, race and competition horses are under a tremendous amount of physical and mental strain, which can contribute to inflammation levels. Those horses affected by COPD are generally systemically inflamed. We are just seeing the evidence manifested in the respiratory diseases.”
SYMPTOMS AND TREATMENTS Symptoms of respiratory disease include reduced perfor- mance, fatigue, chronic cough, shallow coughing when eating and wheezing during exercise. In searching for a diagnosis, “audible noises clue us in
on narrowed airways and mucus accumulations,” explains Dr. Schell, “since we can’t ask a horse to take a deep breath nor to breathe faster on command in order to hear air movement or lack of air movement. We will often place a bag or palpation sleeve over the nose to increase CO2 levels and force them to take a deep breath or two when we remove it.” Bloodwork is also vital in these cases to determine the
presence of secondary inflections that are fairly common due to mucous accumulation, narrow airways and reduced ability to fully ventilate the lungs. For a complete diagno- sis in advanced cases, the veterinarian can sample cells for laboratory analysis by bronchoalveolar lavage, transtracheal washes, endoscopic exams, x-rays of sinus cavities, allergy testing and lung ultrasounds. “It is not uncommon to find specific types of white blood
cells such as mast cells or eosinophils, associated with allergic responses. If there are infections, we often see higher counts of neutrophills, a type of white blood cell associated with infection. We may also find organisms, including bacterial and fungal, which may be primary invaders of secondary in nature,” Dr. Schell continues. The asthma may resolve spontaneously or respond to a wide range of treatments. The goal for all the conditions is
The young filly Nevita had to be treated for asthma twice a day using this equine nebulizer.
Warmbloods Today 31
Courtesy Marsha Busekist
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