Common Equine Respiratory Diseases
Causes
Equine respiratory disease complex (ERDC) is very common among horses. The
stress of hard exercise or transportation, plus exposure to new surroundings and animals, makes
the horse vulnerable to viral infection and secondary bacterial invasion by
Streptococcus zooepidemicus. Streptococcus species are probably the most common
organisms isolated from foals with pneumonia or pulmonary abscesses.
Pneumonia, an inflammation of the lungs, can be caused by viruses (equine viral arteritis,
equine viral rhinopneumonitis) or bacteria. Often, viral pneumonia weakens a horse, allowing
secondary invasion by bacteria.
Symptoms and Diagnosis
Heavy nasal discharge and a fever as high as 107 degrees F (42 degrees C)
are the chief clinical findings. Frequently there is a cough, and sometimes respiratory rates
are increased. An affected horse is usually depressed and refuses to eat. S. zooepidemicus
produces toxins that can injure the airways, leading to pneumonia and abscess formation.
Veterinarians most often make a diagnosis based on clinical experience. Your veterinarian
will most likely want to know the history of the horse and conduct a complete examination
before prescribing a course of treatment.
Management
Successful management of equine respiratory disease depends on a program
of prevention and control:
- Vaccines are available for equine influenza, rhinopneumonitis and strangles. They don't
always prevent infection, but the duration and severity of illness are usually reduced in
horses that have received regular vaccinations. Consult your veterinarian to determine what's
best for your horse.
- Providing a dust- and ammonia-free stable environment for horses with respiratory disease
is very important to reduce irritation and complications of disease.
- Appropriate antibiotic therapy can control bacterial infections.
- The value of enforced rest cannot be overemphasized. Viral infections cause the death and
shedding of respiratory epithelium, a membranous cellular tissue that lines the airways and
produces secretions that protect the underlying cells. Even after the horse appears to have
recovered, three more weeks of rest are required to allow the epithelium to regenerate. Exercising
a horse too early, before it can fully clear inhaled particles from the respiratory tract,
leaves it susceptible to secondary infections.
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