Lecture 40: Diseases and Disorders of the Lower Respiratory Tract 1

severe equine asthma

naturally occurring respiratory disease characterized by periods of reversible airway obstruction caused by neutrophil accumulation, mucus production, and bronchospasm

SEA incidence

• 12% mature horses

• >50% horses with respiratory disease

SEA clinical signs

• cough, ± nasal discharge

• poor performance

• dyspnea

SEA diagnosis

• endoscopy

• BALF

what are the 2 forms of SEA?

recurrent airway obstruction and summer pasture associated obstructive pulmonary disease

recurrent airway obstruction

stabled horses, get better on pasture

summer associated obstructive pulmonary disease

pastured horses, stay sick on pasture

3 main events for SEA

• airway obstruction

• airway inflammation

• mucus accumulation

most frequent clinical signs for SEA

• cough with or without nasal discharge

• various degrees of expiratory dyspnea

• nasal flare and abdominal push

• normal or increased RR, exercise intolerance

clinical signs for severe cases of SEA

• exercise intolerance, weight loss

• hypertrophy of external oblique and rectus abdominis

• pulmonary hypertension

• may evolve to obvious wheezing and severe distress

SEA diagnosis

• history and PE → clinical scores and auscultation

• endoscopy → mucus accumulation, tracheal hyper-reactivity

• respiratory samples → TW and BALF

• BALF > 15% neutrophils

SEA diagnostic testing

• hematology and serum biochemistry → normal

• radiographs → limited value

• skin testing → limited value

• pulmonary function testing → advanced test

SEA treatment and prognosis

• environmental control

• medical treatment → systemic, local

• prognosis → affected horses will always be susceptible

SEA treatment

• environmental control = reduce dust

• options for bedding → low dust shavings, paper, cardboard

• options for hay → avoid hay (silage, pelleted), soaked, on the ground

• options for management → storage, cleaning

SEA corticosteroids

• systemic (laminitis risk) → dexamethasone, prednisolone

• inhaled → beclomethasone diproprionate, fluticasone propionate, ciclesonide

SEA bronchodilators

• beta2 adrenergic agonists → clenbuterol, terbutaline sulfate, etc

• methylxanthines

• anticholinergics → atropine, ipratropium bromide

SEA mucolytics

acetylcystein

aservo equihaler

• adapted to the horse

• soft mist technology

• prodrug ciclesonide

• severe asthma

• day 1-5: 8 puffs bid, day 6-10: 12 puffs sid

• 10-15 day treatment

mild equine asthma

• poor performance, exercise intolerance or coughing with or without excess tracheal mucus

• non-septic LRT inflammation detected on BALF cytology

• pulmonary dysfunction

heaves/SEA

• older horse

• increased RR, dyspnea

• broncho-interstitial pattern on radiographs

• increased % neutrophils on BALF cytology

• good response to environmental control

MEA

• all ages

• RR normal, no dyspnea

• no changes in radiographs

• increased neutro/eosino/mast cells on BALF cytology

• variable response to environmental control

MEA clinical signs

• poor performance

• difficult recovery after exercise

• accumulation of mucus

• cough, nasal discharge

• no dyspnea

• no systemic signs

• no CBC

• no clin path

MEA diagnosis

• history and PE

• tracheo-bronchial endoscopy → mucus, hyperreactivity

• BALF cytology

MEA treatment

• environmental control

• medical treatment → corticosteroids, bronchodilators, omega 3 fatty acids, sodium cromoglycate, acetylcystein, antibacterials