Equine Asthma, a term that encompasses various syndromes including Inflammatory airway disease (IAD) and Recurrent airway obstruction (RAO).
Inflammatory airway disease (IAD)
Characterized as exercise intolerance and intermittent cough in horses that are normal at rest
Inflammatory condition of the lower respiratory tract
Appear to be primarily noninfectious
Occurs in 22%–50% of athletic horses
Is a common cause of impaired performance and interruption of training
Recurrent airway obstruction (RAO)
Characterized as heaves, broken wind, and chronic airway reactivity Is a common respiratory disease
Unlike IAD, horses with RAO don’t breathe normally at rest
Usually suffer from a persistent cough
Airway obstruction episodes occur when a susceptible horse is exposed to common allergens
Unlike inflammatory airway disease, horses with RAO don’t breathe normally at rest and usually suffer from a persistent cough. Airway obstruction episodes occur when a susceptible horse is exposed to common allergens.
RAO symptoms include chronic cough, nasal discharge, and trouble breathing. The classic “heave line” that can appear along the bottom edge of the ribs (figure 2) occurs when the abdominal muscles become large from excess work. Severely affected horses may also exhibit weight loss, anorexia, and exercise intolerance.
Figure 2 (heave line)
There are two forms of RAO: The barn-associated type, often occurring in stalled horses fed hay and summer pasture-associated, seen more commonly in horses living on pasture in the Southeast.
Most evidence suggests RAO is the result of the lung’s hypersensitivity to inhaled antigens. The most common allergic triggers are mold, organic dust, and endotoxin in hay and straw.
Although relief medications will alleviate clinical RAO symptoms, the respiratory disease will return if the horse remains in the same environment once the medications are discontinued. Since bronchodilators have minimal to no anti-inflammatory activity, they should not generally be the sole treatment for RAO.
RAO is a chronic disease, requiring life-long management. Hyposensitization, alongside environmental and dietary management may help reduce the clinical symptoms of RAO.
Common mold & barn allergens
CLADOSPORIUM Grows on plants, leather, rubber, cloth, paper, & wood
ASPERGILLUS Found in soil, damp hay, grain, & fruit
PENICILLIUM Grows in soil, decaying vegetation, breads, fruit, & cheese *Not to be confused with an allergy to the medication Penicillin
ALTERNARIA Grows on textiles, soil, seeds, plants, & horizontal surfaces in water damaged buildings
SMUTS Found on corn, grasses, weeds, flowering plants, & other fungi; wind disseminated
CANDIDA ALBICANS Found in soil, organic debris, & in humans as an organism in the nasal cavity & feces
PHOMA Grows in damp/humid areas on paper products, soil, & dead plants
MUCOR Found in leaf litter, organic debris, & animal waste
HELMINTHOSPORIUM Parasite found on cereals, grasses, sugar cane, soil, & textiles