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
What 3 classes of bronchodilators are used to treat recurrent airway obstruction?
- beta-2 adrenergic agonists: Clenbuterol, Terbutaline sulfate, Fenoterol, Albuterol, Pirbuterol, Salmeterol
- methylxanthines: theophylline, pentoxifylline
- anticholinergics: Atropine, Ipratropium bromide
What mucolytic is used to treat recurrent airway obstruction?
acetylcystein
What are 3 possible metered dose inhalers used to treat recurrent airway obstruction?
- Aeromask
- Aerohippus
- Equine haler
What are 3 possible nebulizers used to treat recurrent airway obstruction?
- Jet/Ultrasonic/Mesh
- Nebul
- FlexiNeb - whole apparatus is on the horse
What is the Aservo Equihaler? What drug is found in it? How does it compare to other nebulizers and inhalers?
a device specifically adapted to the horse nostril that uses slower soft mist technology to deliver an inhaled corticosteroid
prodrug Ciclesonide becomes Des-Ciclesonide upon contact with airway epithelium —> less side effects!
drug already comes in the device with a 10-15 day treatment that cannot be switched or replaced
What is the recommended treatment schedule with the Aservo Equiphaler?
DAYS 1-5 = 8 puffs BID
DAYS 6-10 = 12 puffs SID
What are the 3 major characteristics of inflammatory airway disease (mild equine asthma)?
- poor performance, exercise intolerance, or coughing +/- excess tracheal mucus
- non-septic lower airway inflammation on BAL fluid cytology
- pulmonary dysfunction
In what horses is inflammatory airway disease (mild equine asthma) most common? What are possible triggers?
young performance/race horses
- bacteria
- virus (influenza)
- exercise-induced pulmonary hemorrhage
- environment
- inhaled gases/particles
- hypersensibility
How do clinical signs, radiography, and BALF cytology compare in severe and mild equine asthma?
SEVERE = increased RR and dyspnea; broncho-interstitial pattern, increased neutrophils (>15%)
MILD = normal RR and NO dyspnea, no changes, increased neutrophils, eosinophils, and mast cells
What are the 4 most common clinical signs associated with mild equine asthma? What is not seen?
- poor performance
- difficult recovery after exercise
- accumulation of mucus
- cough, nasal discharge (variable)
- dyspnea, systemic signs
- CBC or clinical pathological changes
How should BAL fluid cytology in a patient with mild equine asthma look? What is seen in healthy patients?
MEA = >10% neutrophils, >5% eosinophils, >5% mast cells
NORMAL = < 5% neutrophils, <1% eosinophils, <2% mast cells
What medical treatment is recommended for mild equine asthma?
- corticosteroids
- bronchodilators
- acetylcysteine (mucolytic)
- antibacterials for isolated infections
What additional medications have anti-inflammatory effects and are able to stabilize mast cells?
omega 3 fatty acids (DHA)
sodium cromoglycate
