Equine Respiratory Diseases Quiz

Equine Lower Respiratory Tract Disorders

• Learning Objectives:
  • Develop understanding of common conditions affecting the lower respiratory tract of the horse.
  • Describe diagnostic modalities used to investigate respiratory conditions in horses and understand their benefits.
  • Outline diagnosis, treatment, and control of infectious respiratory disease in horses.

Signs of Airway Disease in Horses

• Cough
• Nasal discharge
• Abnormal breathing patterns/sounds

Abnormal Breathing Patterns in Horses

• Normal:
  • Respiration in resting adult horses is slow (8-16 breaths/min).
  • Minimal chest and abdominal wall movement.
  • Costo-abdominal movement (slight movement of costal arch followed by slight end-expiratory abdominal lift).
  • Slight movement of the nostrils.
• Abnormal:
  • Increased rate and depth.
  • Changed breathing pattern.
  • Abnormal sounds associated with breathing.
  • Note: Ponies may have slightly higher resting respiratory rates (upto 20 breaths/min).

Expiratory Dyspnea

• Exaggeration of biphasic expiratory phase.
• Increased incorporation of abdominal muscles.
• Obvious biphasic or double expiratory lift ('heave').
• Typical for small airway obstruction.
• Associated with stertorous or stridorous noise during inspiration.

Inspiratory Dyspnea

• Indicative of upper airway obstruction.
• May occur with severe restrictive lung diseases (e.g pneumonia, interstitial disease, pneumothorax, rib fracture).
• Usually with tachypnoea.
• Suggestive of severe upper or lower airway obstruction, diffuse pulmonary disease or pleural disease.

Combined Inspiratory & Expiratory Dyspnea

• Suggestive of severe upper or lower airway obstruction, diffuse pulmonary disease or pleural disease.
• Associated with rapid, shallow breathing.

Understanding Abnormal Auscultation Sounds - Clinical Implications

• Normal lung sounds: Vary depending on body condition and depth of breathing.
  • Can be accentuated in fat horses by using re-breathing bag.
  • Most intense over the distal cervical trachea and carina.
  • May be difficult to perceive at the lung periphery.
• Abnormal lung sounds:
  • Increased audibility of normal breath sounds occur with hyperventilation and in consolidated areas.
  • Suggests lower airway disease (e.g inflamed airways).
  • Reduced audibility in obese horses.
  • Absence of sounds in ventral thorax (may be bilateral) suggests pleural effusion.
  • Absence of sounds in dorsal thorax suggests pneumothorax.
• Adventitious sounds: Crackles, wheezes and pleural friction sounds.

Equine Lower Respiratory Tract Disorders - Classification

• Classification of Equine Respiratory Disease: Infectious vs Non-infectious (contagious/non-contagious). Infectious further subdivided into Bacterial, Viral and Parasitic. Non-infectious further subdivided into inflammatory, airway disease, neoplasia and other.
• Includes detailed information differentiating between upper and lower respiratory tract disorders based on symptoms.

Diseases of the Airways

• Asthma (Mild/Severe, also IAD, Inflammatory Airway Disease, RAO, Recurrent Airway Obstruction)
• Infectious airway diseases (specific examples not listed)

Diseases of the Lung Tissues

• Pneumonia, Bacterial, Sterile (Chronic Interstitial Inflammatory Infiltrates/pneumonitis), Equine Multinodular Pulmonary Fibrosis, Neoplasia, Other (e.g, Exercise-Induced Pulmonary Haemorrhage, Congestive Heart Failure)

Equine Asthma

• Severe Equine Asthma (SEA): includes Equine Pasture Asthma.
• Mild/Moderate Equine Asthma (MEA): characterised by a poor performance condition commonly found in young horses.

Mild Equine Asthma (MEA)

• Clinical picture: Common in young performance horses, any age - young > older, subacute-chronic presentation, poor performance, intermittent cough (often only 38% of cases).
• Causation: Poor ventilation, dusty hay/bedding, NH3/H2S, infectious agents.

Severe Equine Asthma (SEA)

• Clinical Picture: Common in mature horses and ponies, typically older, subacute-chronic presentation, audible abdominal effort/nostril flaring, coughing, 'wheezes and crackles".
• Causation: Poor ventilation, dusty hay/straw bedding (moulds), NH3/H2S, seasonal environmental allergens (e.g pasture asthma)

Severe Equine Asthma - Pathophysiology

• Airway hyperresponsiveness, inflammation, airway wall thickening, increased mucus production, bronchospasm, and airway remodeling.
• Main characteristic is reversible airway obstruction.

Thoracic Neoplasia (Primary and Metastatic Tumours)

• Primary Tumours: Granular cell tumor (myoblastoma) is the most common primary lung tumour. Average age of horses affected is 13 yrs but affected racehorses can be younger.
• Metastatic Tumours: media-stinal lymphoma which commonly affects mature to elderly horses, as well as other types of metastatic tumours such as Hemangiosarcoma, Adenocarcinoma, Melanoma and Squamous cell carcinoma.

Exercise-Induced Pulmonary Haemorrhage (EIPH)

• Clinical picture: Bleeding from the caudodorsal lung lobes during exercise.
• Consequences: Depends on many risk factors, Intensity, duration, fitness, harder tracks (faster), cooler temperatures.
• Horses less likely to bleed if they are: Fitter, lighter, healthy, non-inflamed airways, no respiratory obstructions (upper or lower), normal cardiac output.
• Prevalence: Epistaxis, Tracheal endoscopy, repeated endoscopy, bronchoalveolar lavage.

Congestive Heart Failure

• Clinical picture: Mitral insufficiency, rare, tachycardia, severe left-sided systolic murmur; pulmonary oedema, white frothy nasal discharge.
• Treatment: might respond to digoxin/furosemide in short-term, benazepril.

Diagnostic Approaches for Lower Tract Respiratory Disorders in Horses

• Multifaceted Approach: History/signalment, clinical signs, blood tests, endoscopy findings, airway cytology, airway microbiology.

Clinical Examination

• General: Rectal temperature (normal vs abnormal), nasal discharge (assessment of quality, quantity), lymph nodes, laryngeal squeezing, lung sounds (auscultation - crackles, wheezes, silence), rebreathing bag, coughing, heart.

Clinical Differentiation of Airway Diseases

• Tables present a comparison of characteristics (age, time, fever, cough, nasal discharge, heaving/nostril flare) for infectious airway diseases, MEA, and SEA.

Haematology/Acute Phase Proteins

• Normal versus abnormal results for horses with suspected respiratory issues, such as neutrophilia or SAA.

Visual Assessment of Airway – Endoscopy

• Examination of the airway using endoscopy, grades for the severity of mucus present.

TW vs BAL - Diagnostic Value

• Comparison of tracheal wash versus bronchoalveolar lavage for use in diagnosis of respiratory disease. Detailed data of performance in use.

TW and BAL Cytology in Disease

• Table showing cytological findings in TW and BAL for different conditions (infectious airway disease, MEA, SEA).

References (Page Numbers 42-43)

• List of references provided for further study.