Equine LRT Disorders Flashcards
- Main thing to look for on endoscopy of LRT?
- Other things to assess for on endoscopy.
- Mucus.
- Blood.
Sensitivity of trachea.
Structural abnormalities.
FB.
Thickening of the carina (blunting = oedema and remodelling).
- How does mucus accumulation occur?
- Mucus when disease present.
- Imbalance of secretion and clearance.
- Composition change - thickened so airway obstruction.
Colour and opacity changes.
- How can cytology of TW and BAL samples indicate severity of disease?
- Why is cytology on TW samples more difficult?
- Based on proportions of inflammatory cells.
- some labs give percentages of the cells that are present.
- other labs will give categories and estimates of numbers for TW e.g. +, ++, +++, -. - Cells more likely degenerate and trapped in mucus.
- Normal cells in TW cytology.
- What about TW cytology in disease?
- Epithelial cells.
Macrophages.
<20% neutrophils.
<1% eosinophils.
<1% mast cells. - Neutrophilia.
Occasionally eosinophilia and mast cell response.
- BAL cytology normal findings.
- Most common inflammatory response in horses.
- Macrophages (~60%; 40-80).
Lymphocytes (~35%; 20-50).
Neutrophils (<5%).
Mast cells (<2%).
Eosinophils (<1%). - Neutrophilia - irrespective of if infectious or non-infectious.
TW culture.
Normal bacterial flora of conducting airways.
True infection - pure growth of single organism.
Impaired mucociliary clearance.
- inflammatory/allergic.
Contamination during the procedure.
- e.g. pseudomonas due to poor cleaning of endoscope.
- What is equine asthma.
- Umbrella term.
LRT disease resulting from airway inflammation.
Resulting from small airway obstruction caused by an immune-mediated hypersensitivity to inhaled particles in more severe cases.
Most common non-infectious respiratory disease.
Most common cause of coughing in adult stabled horses.
Equine asthma pathogenesis.
Airway inflammation leads to airway obstruction due to:
- Bronchospasm (smooth muscle contraction).
- Mucus accumulation.
- Airway wall changes cased by oedema, inflammation and remodelling (severe and chronic). .
- Prevalence of mild to moderate equine asthma.
- Mild to moderate equine asthma age of horses affected.
- Severe equine asthma age of horses affected?
- Prevalence of severe equine asthma.
- > 70%.
- Any age.
- Middle aged-older (av. 9yo onset).
- 10-15%.
Mild to moderate asthma clinical signs.
Often subtle.
Poor performance/lack of energy.
Prolonged recovery from exercise.
Cough (~30%).
Nasal discharge (serous-mucoid - most commonly just post exercise).
No increased respiratory effort.
Not systemically ill, not off-colour.
Severe equine asthma clinical signs.
Chronic presentation more common than acute.
Coughing.
Tachypnoea/dyspnoea.
Exercise intolerance.
Nasal discharge.
Nostril flaring.
Heave line (increased abdominal expiratory effort).
- What is heard on auscultation of horses presenting w/ asthma?
- What can be done to make respiratory auscultation easier?
- Abnormal breath sounds e.g. expiratory wheezes, crackles.
- Rebreathing bag - makes auscultation more sensitive as makes horse breathe much more deeply.
- DO NOT USE IN ACUTELY DYSPNOEIC!
Dx of equine asthma.
CE.
Not w/ blood tests.
Endoscopy - increased tracheal mucus.
- blunting of carina in severe cases.
TW/BAL - neutrophilic inflammation (increases w/ severity of disease)
– DO NOT PERFORM IN ACUTELY DYSPNOEIC PATIENTS.
– less commonly mixed inflammatory response (eosinophils, mast cells).
Trial treat bronchodilator - IV Buscopan, Clenbuterol or atropine.
Mild to moderate equine asthma Tx.
Aim to decrease environmental dust and control airway inflammation.
- Environmental management.
- Corticosteroids – control inflammation.
- Advantages of inhalation and nebuliser therapy.
- Disadvantages of inhalation and nebuliser therapy.
- High local conc. in airways.
Rapid onset action.
Reduced total dosage.
Decrease risk of side effects.
Reduced detection time in competition horses. - Poor access to restricted airway.
- may be more advantageous to start w/ oral meds and transfer to inhaled once condition more stable.
Lack of patient/owner compliance.
Tx of acute severe asthma?
Remove from stable.
Administer bronchodilator for immediate relief of airway obstruction:
- IV Buscopan.
- IV Clenbuterol (side effects sweating, tachycardia).
- IV atropine (side effect ileus).
Corticosteroids - reduce inflammation:
- IV dexamethasone (care - laminitis).
- What is the more common indication for use of Buscopan?
- Colic.
Tx of chronic severe asthma?
Environmental management to reduce allergen exposure.
Corticosteroids reduce inflammation:
Prevent tolerance to B2.
- e.g. oral prednisolone.
- e.g. inhaled cicelsonide, fluticasone.
- side effect laminitis.
Bronchodilators relieves obstruction:
- B2 agonists.
- oral Clenbuterol (Ventipulmin).
- inhaled/nebulised salbutamol/salmeterol/clenbuterol.
- not used alone, adjunct only.
Mucus clearance drugs:
- e.g. Bisolvon (bromhexine), dembrexine (sputolosin), clenbuterol (ventipulmin).
- inhaled saline and inhaled acetylcisteine used in performance horses.
- little evidence but mucus production will resolve w/ improvements in airway inflammation – down-regulation of goblet cells.
Environmental risk factors for equine asthma.
Stabling v field - stabling normal horse will cause airway inflammation.
Reduced ventilation e.g. closing barn doors increases dust by 25-30%.
Mucking out - 19x respirable particles.
Mucking out next door - 9x respirable particles.
Hay net - 6x respirable particles compared to feeding from floor.
Environmental management.
Turn out where possible.
Minimise dust in stable by:
- change stable – away from hay store, minimal foot traffic.
- low-dust bedding.
- optimise ventilation.
- remove horse from stable to muck out or sweep.
- Thorough clean – remove all dust and cobwebs and power hose floor to decrease ammonia.
- hose down yard/alleys.
- manage adjacent stables the same.
Feeding asthmatic horses.
Dry hay the worst.
Soaked/steamed hay good as long as fed when wet.
Steamed better than soaked as bacteria/mould increases w/ soaking.
Haylage is good.
- SPAOPD stand for?
- What is SPAOPD.
- When does SPAOPD occur?
- Tx?
- Summer pasture associated obstructive pulmonary disease.
- Similar to severe asthma but trigger is pasture environment.
- likely due to hypersensitivity to environmental allergens like pollen/mould. - Late spring to early summer.
- As for asthma except horse should be removed from pasture.
- EIPH stand for?
- % horses found to have blood in trachea after racing.
- Origin?
- Exercise induced pulmonary haemorrhage.
- 75%.
- Haemorrhage originates from caudo-dorsal lung lobes.
- EIPH main aetiology.
- Other contributing factors to EIPH?
- Stress failure of pulmonary capillaries.
- high pulmonary intracapillary pressure and negative inspiratory pressures w/in airways leads to rupture of the capillary wall. - Poss. association between lower airway inflammation and EIPH.
Upper airway obstruction (e.g. RLN) may exacerbate EIPH.
Associated w/ AF.
EIPH clinical signs.
Epistaxis.
Reduced exercise tolerance (probably due to volume of haemorrhage).
Prolonged post-exercise recovery.
EIPH Dx.
Endoscopy - blood in trachea.
TW/BAL - RBCs and haemosiderin-laden in less obvious cases.
Thoracic radiographs - caudo-dorsal lung field opacity (not used often clinically).
EIPH Tx.
Eliminate any potential underlying cause (asthma, URT obstruction, AF).
Attempt to reduce severity.
USA not UK - frusemide (Lasix).
Nasal dilator strips (UK eventing, not racing).
Immunomodulators - airway inflammation.
Bacterial pneumonia/pleuropneumonia in horses.
Needs a predisposing event that suppresses pulmonary immunity - very rarely primary disease.
Bacterial pathogens invade LRT - mixed infections common.
Predisposing events for bacterial pneumonia/pleuropneumonia.
Inhalation of feed material
- e.g. choke/dysphagia.
Airway FB.
GA.
Stress/long distance travel (shipping fever) - restricted from lowering head so reduced mucociliary clearance.
Post viral infection.
Penetrating trauma.
Bacterial pneumonia/pleural pneumonia clinical signs.
Fever, depression, lethargy, cough, nasal discharge.
Pleural effusion.
- Pleural pain (pleurodynia, endotoxaemia.
– Rapid shallow breathing.
–> Severity dept. on vol pleural effusion and extent of pulmonary consolidation.
—> Lack of breath sounds ventrally and abnormal sounds dorsally on auscultation.
Bacterial (pleuro)pneumonia Dx.
Blood sample: High WBC and fibrinogen.
Bacterial culture of pleural fluid and TW/BAL samples.
Thoracic US.
Thoracic radiography.
Thoracocentesis.
Bacterial (pleuro)pneumonia Tx.
Broad spectrum ABX.
Supportive care - NSAIDs, fluid therapy, nutritional support.
Thoracocentesis and drainage.
