The First Annual Frank Milne Lecture Awarded

The Frank Milne Lecture at this year's American Association of Equine Practitioners' convention was a first. It was designed to present what amounted to an A-to-Z informational session on a given subject. Chosen for this year was the lower airway of the horse. Selected to present the information was N. Edward Robinson, B. Vet Med., PhD, MRCVS, of Michigan State University (and a member of The Horse Editorial Advisory Board). Robinson is the Matilda R. Wilson Professor of Large Animal Clinical Sciences at the university.

The lecture series, which is to become an annual event, was named for Frank Milne, who for years edited the AAEP convention Proceedings book. He was the organization's first Canadian member, and he served as an AAEP president.

Robinson started by going back to the basics for an audience that packed the ballroom for the four-hour session. He discussed the tracheobronchial tree that delivers and distributes air within the lung, then went on to explain how inflammation in the airways of young horses begins to compromise the system. He discussed how severe airway obstruction in older animals is the result of repeated exposure to dusts, molds, and other contaminants.

"In addition to delivering air for gas exchange," Robinson said, "the tracheobronchial tree protects the lung from inhaled irritants such as dusts and pollutant gases, from antigens, and infectious agents. The defense mechanisms of the airways include cough, the mucociliary system, phagocytes, smooth muscle, and the bronchial circulation. These mechanisms prevent penetration of inhaled materials deeper into the lung and assist in the neutralization and elimination of such materials."

When the tracheobronchial tree suffers inflammation from infection, allergy, or environmental contamination, it is unable to carry out its assigned duties of gas exchange and protection. Acute bouts of inflammation, Robinson said, cause mucus secretion, airway wall thickening, and increased responsiveness of reflexes that initiate cough and bronchospasm. These continued attacks lead to changes in the mucosa and the smooth muscle to the point that the airway walls are thickened.

Prevention of inflammation through control of environment and feed was at the heart of Robinson's message.

"Improving air quality in the horse's environment is the most important step in the prevention and treatment of equine lower airway disease," he said. "This can be done in several ways—by removing point sources of dust, by instituting a low-dust management scheme, and by improving overall ventilation."

Ideally, he said, horses, especially those suffering from respiratory ailments, should be kept outdoors on pasture and should be fed dust-free hay when pasture is unavailable. Continuing in a dust-polluted environment, he indicated, results in inflammation in the lower airways of young horses that can lead to chronic obstructive pulmonary disease (COPD) as they grow older.

When airway obstruction must be treated, he said, bronchodilators can be effective because airway obstruction is primarily a result of bronchospasm, and bronchodilators can provide relief from respiratory distress. However, he emphasized, bronchodilators do not produce a cure; they merely provide symptomatic relief and do not attack the underlying problem of airway inflammation.

"When airway inflammation cannot be resolved by changes in management," he told the group, "anti-inflammatory therapy is needed. Corticosteroids are still the drug of choice. The treatment of human asthma has been revolutionized by the use of inhaled steroids. Asthmatics monitor their own lung function and adjust their steroid dose accordingly. A similar treatment modality should be our goal in veterinary medicine. The use of inhaled steroids for treatment of horses is becoming practical as convenient devices reach the market."

Robinson went into detail on the medications that are available today as well as the techniques and devices used to administer them.

About the Author

Tim Brockhoff

Tim Brockhoff was Staff Writer of The Horse:Your Guide to Equine Health Care from 1995 to 1999. His degree is in Agricultural Communications from the University of Kentucky, and his equine experience is with American Saddlebreds.

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