Diseases of the Lower Respiratory Tract Flashcards
What are the 2 forms of asthma in horses?
- SEVERE = recurrent airway obstruction (COPD, heaves)
- MILD = inflammatory airways disease
What is recurrent airway obstruction?
naturally occurring respiratory disease characterized by periods of reversible airway obstruction caused by NEUTROPHIL accumulation, mucus production, and bronchospasm
- severe equine asthma
- COPD
- heaves
What is the most common etiologies of recurrent airway obstruction?
mixture of inhaled dust and allergens
- BACTERIA: endotoxins, lipoteichoic acid, peptidoglycan, DNA, proteases, toxins
- MOLDS: allergens, glucans, proteases, mycotoxins
- FORAGE MITES: allergens, proteases
- PLANT DEBRIS
- INORGANIC DUST COMPONENTS
- NOXIOUS GASES: ammonia, hydrogen sulfide, methane
In what horses is recurrent airway obstruction most common?
middle-aged horses housed in dusty barns
- no breed
What are the most common clinical signs associated with recurrent airway obstruction?
- chronic cough +/- mucoid nasal discharge (bronchial hyperreactivity)
- poor performance
- expiratory dyspnea (flared nostrils, abdominal effort)
- heaves line
- normal or increased respiratory rate with exercise intolerance
In what 3 ways is recurrent airway obstruction diagnosed?
- auscultation = wheeze and crackles
- endoscopy shows increased mucus and induces tracheal hyperreactivity
- BAL fluid cytology rich in neutrophils (>15%)
Mild vs severe equine asthma:
What are the 2 forms of recurrent airway obstruction?
- recurrent airway obstruction - common in winters up north, where horses are stabled and get better when put out in pasture
- summer pasture associated obstructive pulmonary disease - common in the south where horses are allergic to pollen or something else in the environment and remain sick in the pasture
What are the 3 events that take place in recurrent airway obstruction? What does this result in?
- airway obstuction
- airway inflammation
- mucus accumulation
narrow airway causes an increased effort in expiration
What are 4 signs of severe cases of recurrent airway obstruction?
- exercise intolerance and weight loss
- hypertrophy of external oblique and rectus abdominus
- pulmonary hypertension
- obvious wheezing and severe distress
Why is additional diagnostics other than a physical exam, endoscopy, and BAL fluid cytology usually not necessary?
- hematology and serum biochemistry will be normal
- radiographs and skin testing for allergens have limited value
- pulmonary function testing is very advanced, with not much extra information given
What is the prognosis of recurrent airway obstruction like?
very controllable, but affected horses will always be susceptible
In what 4 ways can the environment be controlled to help treat recurrent airway obstruction?
- let horse out on pasture more often and while the barn is being cleaned
- use low dust shaving, paper, or cardboard for bedding
- use silage and pelleted feed over hay or soak it (lowers nutrition) and feed it on the ground
- keep hay stored away from affected horses
environmental change may be sufficient to resolve clinical signs, but is the most difficult to institute is horses remain in a barn
What 2 systemic corticosteroids are commonly used to treat recurrent airway obstruction? What risk is associated?
- Dexamethasone
- Prednisolone
start high and taper to lowest therapeutic dose
increased risk of Founder, or laminitis
What 3 inhaled corticosteroids are used to treat recurrent airway obstruction? How do they compare to systemic corticosteroids?
- beclomethasone diproprionate
- fluticasone propionate
- ciclesonide (specific for horses)
- less likely to develop side effects
- $$$
- typically used several times a day
