heaves Flashcards
what is heaves (RAO)?
RAO used to be called COPD: Chronic Obstructive Pulmonary Disease
• Inflammatory and obstructive airway disease that afflicts older horses
• Initiated by inhalation of organic dusts: dusts associated with hay, bedding, etc
• Organic dusts: allergens, endotoxins, molds, other particles that can initiate lung inflammatory response
Horse responds with severe inflammatory process and also bronchoconstriction
• More prevalent in Northern Hemisphere: horses are stabled and fed hay
• Apparent genetic component: horses housed under same environmental circumstances: heaves in susceptible horses while not affecting stable mates
heaves disease process
When susceptible horses are moved from pasture to stable and fed hay, a massive influx of neutrophils that invade the airway lumen happens within 6 to 8 hours.
• Inflammatory mediators (IL, cytokines, leukotrienes) acting on cholinergic nerves are responsible for bronchospasm
• Increased mucus production and viscosity leads to mucus accumulation
• Airway wall thickening: edema (acute) and remodeling (chronic)
• Hyperresponsiveness
clinical signs of heaves
Airway obstruction occurs concomitantly with inflammatory process bronchospasm, mucus accumulation and airway wall thickening
• Inflammatory process is more important than bronchoconstriction and needs to be treated
marked respiratory distress
marked respiratory distress
Acute episode: flared nostrils, ↑ respiratory rate, use of abdominal muscles to assist expiration, anxious appearance
– Horse becomes intolerant to exercise
– Advanced stages: struggle to breathe is so intense
that horse is unable to eat and loses weight
– Use of abdominal muscles to assist expiration: heave lines
history of affected horses
7 years or older
– Cough: when dust levels are increased feeding time, cleaning barn, or exercise
– Prolonged recovery from exercise, nasal discharge, abdominal effort during breathing, exaggerated breathing pattern for the level of exercise
– Severe stages: respiratory distress at all times, specially if horse is stabled
diagnosis
based on history and typical clinical signs
what is RAO similar to?
summer-pasture associated obstructive pulmonary disease: warm and humid weather
management and prevention
Environmental Control –Corticosteroids to reduce inflammation
–Bronchodilators to relieve respiratory distress
environmental control
Reductionoreliminationofdustexposure
– Hay and bedding dust: number one to be eliminated. Due to hyperresponsiveness, a little contact with dust can trigger a heaves attack
– Keep horse outdoors year‐round: green pasture is the best. Provide pelleted diet if insufficient grass. Keep horse outside even during winter. Provide shelter (run‐in shed) and blanket. Do not bring horse in due to weather or for grooming
– If absolutely impossible to keep horse outside: soak hay, grass silage, pelleted feed, keep affected horse closer to the door, cardboard bedding (Ecobed) or processed wood shavings (Cleanbox)
anti-inflammatory drugs
NSAIDarecontraindicated:theydecreaseproduction of PGE2, a prostaglandin that inhibits inflammation and prevents bronchospasm
• Corticosteroids:preventpro‐inflammatoryprocess, prevent down‐regulation of β2‐adrenoceptors, increase appetite
• Dexamethasone:Graduallyreducedosetominimum necessary. Improvement in 3‐7 days
• BeclomethasoneandFluticasone:mustbegivenby use of Aeromask (the severity of obstruction prevents the deposition of inhaled steroids in lungs)
bronchodilators
usefulduringanacuteheaves attack (rescue medications)
– Do not treat inflammation
– Should be available to owners at all times
– Improve mucus clearance
– Clenbuterol (Ventipulmin)
– Albuterol, Pirbuterol and Salmeterol: inhalation, must be given by use of Aeromask
– Duration of effect: clenbuterol and salmeterol long acting (6‐8 hrs), albuterol and pirbuterol short acting (1‐2 hrs)
– Sideeffects:sweating,trembling,tachycardia, agitation. Mostly seen with systemic administrations, inexistent when drugs are given via inhalation
prognosis
Depends on stage of disease at which the diagnosis is made and the level of care provided to horse
• Prevention of recurrences of airway inflammation is essential: Rigorous continual prevention of exposure to organic dusts prognosis is excellent
• If total environmental change is impossible: rigorous treatment and prevention of inflammation by corticosteroids, and bronchodilators just prior to exercise
• Under these conditions: horse will be in remission and can still be useful in recreational activities, low to moderate work
• Very few horse owners are willing to undertake the rigorous measures necessary to maintain lung health
is there a cure for heaves
heavesisachronicillness:thereis no cure for heaves. The owner has to manage the environment of their horse to avoid recurrence of heave attacks
– Environmental changes: move horses to pasture with a run‐in shed
– Anti‐inflammatory treatment: corticosteroids
– Bronchodilators: during acute episode, or prior to exercise
