PONCHO'S STORY
~ A HORSE OUT OF BREATH ~
Poncho, a mature Quarter Horse bay gelding was admitted to the Louisiana State University School of Veterinary Medicine's Equine Clinic one year ago, with severe respiratory distress. He was wheezing with each breath and as a result, his nostrils were flared and he had a pronounced heave line. Poncho also had a fever and was depressed. According to Poncho's owner, Mr. Dale Blanchard, the horse had been losing weight for two months as his symptoms worsened.
Veterinarians Elizabeth Vint and Ann Chapman went to work to identify the causes of Poncho's distress. Lab work showed that the oxygen in his arterial blood was very low and the carbon dioxide was slightly increased, despite his great breathing effort. This indicated he was having difficulty ventilating. His weight loss was an apparent result of his unwillingness to eat or drink, since he was devoting all of his energy to getting air into his lungs.
In order to determine whether Poncho's problem was pulmonary, cardiac, related to another organ system, or a combination, Drs. Vint and Chapman recommended an ultrasonographic and radiographic examination of Poncho's chest and heart. However, because of the results of the clinical examination and blood work, Poncho was first administered intranasal oxygen in order to increase his blood oxygen level.
The radiographs revealed changes indicative of airway obstructive disease, like asthma, and no evidence of pneumonia or any other pulmonary disease. The ultrasonographic exam supported the radiographic findings and no cardiac abnormalities were present. So, the good news was that Poncho did not have a heart dysfunction, or a lung infection or a tumor. However, he still had real difficulty breathing. The remaining laboratory work suggested that there was no evidence of systemic infection and all the other organ functions appeared in order, except for the lungs.
A sample from the tracheal secretion was evaluated, which revealed a large number of inflammatory cells known as neutrophils, excessive mucus accumulation and absence of lung infection, confirming the tentative diagnosis of airway disease. Much like asthma, this is an allergic response of the airways which impair the delivery and removal of air into and from the lungs.
The wheezing and labored breathing were due to the obstruction of air flow into the lungs because of the airway inflammation and bronchospasm (constriction of the airway walls). Poncho was given inhaled bronchodilators (albuterol and ipatropium) to relax the airways, improve pulmonary clearance (albuterol) and provide better air movement in and out the lungs. He was also given a systemic anti-inflammatory corticosteroid (dexamethasone) to relieve the inflammation and decrease airway obstruction.
Dr. Vint asked Mr. Blanchard many questions in order to determine which environmental conditions Poncho was exposed to at home in an attempt to identify what might have triggered this severe airway allergy. Mr. Blanchard recalled that Poncho started showing signs of labored breathing while in pasture. Poncho was diagnosed with summer-pasture-associated heaves. Because this is an allergic condition of the airways, just like in human asthma, decreasing exposure to environmental particles that trigger the airway allergic response is critical for improvement of airway function. Poncho was placed in an environment with very little dust (a box stall in a well ventilated area bedded with good quality wood shavings and minimal dust) and he was fed a complete pelleted diet (which means the fiber content is greater than 25%). No hay was given to him.
Scientific investigations performed by LSU Equine Health Studies Program scientists, including Drs. Ralph E. Beadle, Thomas E. Seahorn, Lais R. Costa and their co-workers has indicated that summer-pasture-associated heaves is a seasonal airway disease that appears to be initiated by exposure to certain particulate matter such as mold spores and grass pollens. In addition, removal of the horse from the insulting environment is crucial for clinical recovery. Research by Dr. Costa has shown that mold spores and grass pollens can induce inflammatory cells to produce mediators of inflammation and activate neutrophils, which seem to perpetuate the disease.
Research in several other institutions, including Kansas State University, Tufts University and Michigan State University, have indicated the successful treatment of clinical exacerbation of equine recurrent airway disease with inhaled administration of bronchodilators, such as those given to Poncho.
By the second day of hospitalization, Poncho's breathing was much improved and he again became interested in feed and water. He continued to improve clinically and within two days no longer needed the supplemental oxygen. Within a few days, the dose of anti-inflammatory corticosteroid was gradually decreased until finally it was discontinued. Poncho was discharged with recommendations to minimize exposure to respirable dust particles (such as mold spores and pollens) and to prevent the recurrence of the clinical exacerbation during the late spring to mid fall by maintaining Poncho in a box stall away from the pasture.
This year, Mr. Blanchard reported that Poncho again started to show signs of heaves (coughing and slight increase in respiratory effort). Poncho was removed from pasture and kept in a low-dust environment. The farm veterinarian was called and Poncho responded very quickly to treatment with bronchodilator and anti- inflammatory medication, only having to be medicated for a couple of days. The early recognition and treatment of the problem and the early and aggressive management changes have prevented Poncho from progressing to another episode of severe respiratory distress.
Poncho and many other horses have benefited from the knowledge gained through clinical experience and basic and applied scientific investigation in horses and from the knowledge applied from research in human asthma.
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