gases and atmospheric pollutants (ozone), and/or persistent
respiratory viral infections. Chronic IAD often develops
after overt viral respiratory tract infection and may result
from inability of the immune system to fully eliminate
viruses or bacteria from small airways.
Exercise-induced pulmonary hemorrhage (EIPH) occurs
in the majority of racehorses and is observed sporadically
in many other sports that require strenuous exercise for
short periods of time. The incidence of EIPH in racehorses
is high but the cause and treatment are controversial.
Horseman and track veterinarians generally believe that
EIPH adversely affects performance, and one investigation
demonstrated positive correlation between poor finishing
position and endoscopic identification of blood in the
airway. Conflicting data regarding the impact of EIPH on
race performance may reflect the difficulty in defining
performance and individual performance potential.
Rapid acceleration to high-intensity exercise results in
equally rapid increases in pulmonary arterial and capillary
pressures. Pulmonary capillary pressures are suspected to
exceed the capacity of the pulmonary system to maintain
vascular integrity resulting in “stress failure” of capillaries
and hemorrhage from the pulmonary vascular system.
Some investigators believe that EIPH occurs secondary to
IAD which may result in proliferation of vessels originating
from the bronchial circulation. This region of new blood
vessel formation may be fragile and more prone to rupture
during maximal exercise.
Identification of the ideal therapeutic agent for EIPH that
will eliminate pulmonary hemorrhage without impairing
race performance will not occur until the cause of the
disease is understood. Given the universal nature of this
disease in horses that maintain a high level of performance,
a single agent is unlikely to completely eliminate the
problem in horses that perform high-intensity exercise.
Chronic obstructive pulmonary disease (COPD)
is a chronic, recurrent allergic respiratory disease in
horses exacerbated by exposure to molds in hay and
straw. Obstruction to airflow in small airways results
from bronchoconstriction, excessive mucus production,
and cellular debris. Clinical manifestations of COPD
range in severity from exercise intolerance to labored
breathing at rest. Chronic obstructive pulmonary disease
is uncommon in young racehorses; however low-grade
COPD is an important cause of exercise intolerance and
poor performance in middle-aged horses.
The single most important principle for treatment of
COPD is environmental management directed toward
minimizing antigen exposure. Molds present in hay and
straw are the most common source of antigen; therefore,
affected horses are often successfully maintained in a
pasture environment. If this is unsuccessful or infeasible,
medical management may be necessary. Standard treatment
regimens include anti-inflammatory therapy, bronchodilator
therapy, and broad-spectrum antibiotics. Nonsteroidal anti-
inflammatory drugs and antihistamines are ineffective in
controlling the clinical signs of COPD.
Dr. Craig Sweatt • Dr. Tom Hutchins • Dr. Stacy McLeod
8283 FM 920 • Weatherford, Texas • 817-458-3355
Small Animal •Equine •Livestock •Ambulatory Services
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