Diseases of the Respiratory System: Ch. 11

Overview of the Respiratory System in Small Animals

• Importance of understanding respiratory diseases in veterinary practice.

• Anatomy and physiology of the respiratory system:

  • Upper Respiratory Tract:

    • Nasal passages, pharynx, larynx, trachea.

    • Functions: Warming, humidifying, filtering air.

    • Defenses: Mucociliary escalator, nasal mucosa.

  • Lower Respiratory Tract:

    • Bronchi, bronchioles, alveoli.

    • Gas exchange and cellular defense mechanisms. Role of diaphragm and intercostal muscles in breathing.

Upper Respiratory Tract Diseases

• Canine Infectious Respiratory Disease Complex (CIRDC)

• Etiology: Bordetella bronchiseptica, Parainfluenza virus, etc.

• Clinical Signs: Coughing, nasal discharge, lethargy, fever.

• Pathophysiology: Inflammation of trachea and bronchi.

• Diagnosis: History, clinical signs, PCR, culture.

• Treatment: Antibiotics, antitussives, supportive care.

• Prevention: Vaccination, hygiene, isolation.

Kennel Cough

• The clinical signs of uncomplicated kennel cough are:

  • Dry hacking cough

  • Dry cough which leads to retching/vomiting

  • Sneezing

  • Eye and nasal discharge

• Once your dogdevelops the following signs they are at increased risk of developing pneumonia

  • Fatigue/lethargy

  • Loss of appetite

  • Fever 

  • Difficulty breathing

Feline Upper Respiratory Infection (URI)

• Common Causes: Feline herpesvirus (FHV), Feline calicivirus (FCV), Chlamydia Felis.

• Clinical Signs: Sneezing, nasal discharge, conjunctivitis, anorexia.

• Pathophysiology: Viral invasion of nasal and ocular mucosa.

• Diagnosis: PCR, viral cultures, clinical signs.

• Treatment: Supportive care, antivirals (e.g., famciclovir for FHV).Prevention: Vaccination, isolation.

Feline Calicivirus

1. URT Dz- highly contagious

2. Oral Ulcers: A common symptom is the development of painful ulcers on the tongue and lining of the mouth. 

3. Upper Respiratory Issues: Sneezing, runny nose and eyes, and sometimes drooling are also common. 

4. Lethargy and Lack of Appetite: Infected cats may become less active and lose their appetite. 

5. Fever: A rise in body temperature is a frequent sign of FCV infection. 

6. Lameness: In some cases, FCV can cause a "limping syndrome". 

7. Eye and Nose Discharge 

8. Inflammation of the Gums and Mouth

Lower Respiratory Tract Diseases

• Canine Chronic Bronchitis (CB)

• Common in: Older small breed dogs.

• Etiology: Chronic inflammation (environmental factors like smoke, allergens).

• Clinical Signs: Chronic cough, exercise intolerance, wheezing.

• Pathophysiology: Mucus production, airway remodeling, fibrosis.

• Diagnosis: Clinical signs, radiographs, bronchoscopy, cytology.

• Treatment: Bronchodilators, corticosteroids, weight management.

Feline Asthma

• Etiology: Often triggered by allergens, respiratory infections, or irritants.

• Clinical Signs: Coughing, wheezing, respiratory distress.

• Pathophysiology: Airway inflammation, bronchoconstriction, mucus production.

• Diagnosis: Clinical signs, radiographs, bronchoalveolar lavage.

• Treatment: Corticosteroids (oral or inhaled), bronchodilators, environmental management.

  • Steroids resolve issue by opening up airway quickly

Pneumonia in Small Animals

• Etiology: Bacterial, viral, fungal causes.

• Clinical Signs: Coughing, fever, dyspnea, tachypnea.

• Diagnosis: Thoracic radiographs, blood cultures, PCR.

  • Radiograph should be maily black where lungs are with the outine of the heart

• Treatment: Antimicrobials (based on culture and sensitivity), supportive care.

Pleural Effusion

• Fluid in the chest

• Causes: Heart failure, infections, neoplasia.

• Clinical Signs: Dyspnea, coughing, reduced lung sounds.

• Diagnosis: Thoracic radiographs, ultrasound, thoracocentesis.

• Treatment: Treat underlying cause (e.g., diuretics for heart failure, drainage).

Diagnostic Tools in Respiratory Pathology

• Clinical Examination: History taking, auscultation, and physical exam.

• Radiographs: Identifying pleural effusion, pneumonia, pulmonary edema.

• Endoscopy/Bronchoscopy: Direct airway visualization, biopsy collection.

• Blood Tests: CBC, chemistry, arterial blood gas analysis.

• Advanced Imaging: CT or MRI for detailed lung and airway visualization.

Treatment and Management Strategies

• Surgical options:

  • Tracheal stenting for tracheal collapse.

  • Pleural drainage for pleural effusion.

  • Lung lobectomy for neoplastic lesions or severe pneumonia.

• Pharmacological therapy:

  • Antibiotics, antivirals, antifungals.

  • Bronchodilators (e.g., terbutaline) for asthma/bronchitis.

  • Corticosteroids for inflammation control.

  • Antitussives for cough management (with caution).

Environmental and Supportive Care

• Humidified Air and Oxygen Therapy: Supportive care for respiratory distress.

• Allergen Control: Managing the home environment for asthma.

• Weight Management & Nutrition: Essential for overall health.

Feline Heartworm DZ.

• Not the same or as common as canine heartworm disease.

• One worm can kill a cat (Sudden death)

• Spread by mosquitoes

• Vomiting, cough, wt. Loss

PCR is not typically used in clinics due to the cost of running the test