Bronchitis in dogs encompasses both acute infectious tracheobronchitis (commonly known as kennel cough) and chronic bronchitis. These conditions represent significant categories of canine respiratory disease frequently tested on the NAVLE.
Overview and Clinical Importance
Bronchitis in dogs encompasses both acute infectious tracheobronchitis (commonly known as kennel cough) and chronic bronchitis. These conditions represent significant categories of canine respiratory disease frequently tested on the NAVLE. Understanding the distinction between infectious and non-infectious bronchitis, along with appropriate diagnostic and therapeutic approaches, is essential for clinical practice and board examination success.
Canine chronic bronchitis (CCB) is clinically defined as a cough present on most days for a minimum duration of 2 months, without evidence of other underlying diseases that cause cough. Infectious tracheobronchitis results from inflammation of the upper airways caused by viral and bacterial pathogens, commonly occurring in dogs with exposure to other dogs in kennels, shelters, or boarding facilities.
| Pathogen |
Type |
Clinical Significance |
| Bordetella bronchiseptica |
Gram-negative bacterium |
Primary pathogen; binds to and damages cilia within 3 hours |
| Canine parainfluenza virus |
Virus (Paramyxoviridae) |
Common co-infection; damages mucociliary escalator |
| Canine adenovirus-2 (CAV-2) |
Virus (Adenoviridae) |
Also protects against CAV-1 (hepatitis) |
| Canine influenza virus |
Virus (H3N8, H3N2) |
More severe; higher risk of pneumonia; fatality rate less than 10% |
| Mycoplasma species |
Bacteria (lacks cell wall) |
Contributes to pneumonia progression |
Etiology and Pathophysiology
Acute Infectious Tracheobronchitis (Kennel Cough)
Canine infectious respiratory disease complex (CIRDC) involves multiple pathogens that cause upper respiratory infection. The classic combination is infection with Bordetella bronchiseptica combined with viral agents.
Primary Causative Agents
High-YieldBordetella bronchiseptica can bind directly to respiratory cilia and disable them within 3 hours of contact. It also secretes substances that disable immune cells responsible for bacterial clearance. This makes co-infections common and explains why kennel cough rarely resolves with just antibacterial treatment.
Chronic Bronchitis
Chronic bronchitis results from long-term inflammatory damage to the lower airways. The exact cause is often undetermined, but contributing factors include inhaled irritants (cigarette smoke, air pollution), previous respiratory infections, and possible genetic predisposition to mucociliary clearance deficits.
Pathophysiological Changes
- Epithelial hypertrophy and squamous metaplasia
- Goblet cell hypertrophy with increased mucus production
- Submucosal gland hyperplasia
- Mucosal and submucosal inflammation, edema, and fibrosis
- Smooth muscle hypertrophy
- Ciliary dysfunction leading to impaired mucociliary escalator
NAVLE TipChronic bronchitis can progress to bronchiectasis (permanent airway dilation) and pulmonary hypertension (cor pulmonale). Visualization of bronchitic nodules or airway collapse during bronchoscopy indicates irreversibility of the disease process.
| Infectious Tracheobronchitis |
Chronic Bronchitis |
| Age: Any age; puppies at higher risk
Breed: Any breed
Risk factors:
• Boarding/kennel exposure
• Dog parks, shows, daycare
• Shelter environments
• Stress, overcrowding |
Age: Middle-aged to older (greater than 7 years)
Breed: Small breeds most common; Cocker Spaniels predisposed to bronchiectasis
Risk factors:
• Environmental tobacco smoke
• Air pollution, inhaled irritants
• Obesity
• Previous respiratory infections |
Signalment and Risk Factors
High-YieldOn the NAVLE, when you see an older, small-breed dog with a chronic cough and no systemic illness, think chronic bronchitis first. When you see a young dog with recent boarding history and acute cough, think infectious tracheobronchitis.
| Test |
Expected Findings |
Clinical Significance |
| CBC |
Often normal; may see neutrophilia with infection; eosinophilia suggests EBP or parasites |
Non-specific; helps rule out systemic infection |
| Thoracic Radiographs |
Bronchial pattern: "donuts" (end-on) and "tramlines" (longitudinal); peribronchial cuffing; hyperinflation |
Limited sensitivity (65%); helps rule out heart disease, masses, pneumonia |
| Bronchoscopy |
Hyperemic, irregular mucosa; increased/thick secretions; bronchiectasis; dynamic collapse |
Gold standard for visualization; identifies concurrent tracheobronchomalacia (50% of cases) |
| BAL Cytology |
Neutrophilic inflammation (greater than 8% neutrophils); increased mucus; Curschmann spirals |
Supports diagnosis; differentiates from EBP (eosinophilic); normal: 65-85% macrophages, less than 5-8% neutrophils/eosinophils/lymphocytes |
| BAL Culture |
Often negative or low growth; significant growth: greater than 1.7 x 10^3 CFU/mL |
Chronic bronchitis typically NOT associated with significant bacterial growth |
Clinical Signs
Infectious Tracheobronchitis
- Characteristic dry, high-pitched, "honking" cough
- Cough often followed by gagging or retching
- May cough up mucus
- Coughing exacerbated by activity or tracheal palpation
- Watery nasal discharge possible
- Usually otherwise bright, alert, and active (uncomplicated)
Complicated cases (progression to pneumonia) may show: fever, lethargy, anorexia, labored breathing, and productive cough. Puppies and immunocompromised dogs are at highest risk.
Chronic Bronchitis
- Daily cough for greater than 2 months
- Harsh, dry, non-productive cough (may become productive)
- Cough often ends with gagging or retching
- Exercise intolerance
- Cyanosis and exhaustion in severe cases
- Syncopal episodes possible (from severe coughing paroxysms)
- Otherwise systemically healthy (no fever, lethargy, or anorexia)
Physical Examination Findings
- Auscultation: Inspiratory and expiratory crackles (most consistent finding); wheezes may indicate bronchoconstriction
- Tracheal sensitivity: Positive tracheal pinch test (induces coughing)
- Heart rate: Normal to slightly decreased; sinus arrhythmia common
- Increased expiratory effort: Suggests intrathoracic airway disease
| Drug Class |
Drug |
Dose |
Notes |
| Antitussive |
Hydrocodone |
0.22 mg/kg PO q6-12h |
Contraindicated if pneumonia present |
| Antitussive |
Butorphanol |
0.5 mg/kg PO q6-12h |
Alternative antitussive |
| Antibiotic |
Doxycycline |
5 mg/kg PO q12h x 7-10 days |
First-line for Bordetella; bacteriostatic |
| Antibiotic |
Azithromycin |
5-10 mg/kg PO q24h x 5-7 days |
Good respiratory tissue penetration |
Diagnosis
Chronic bronchitis is largely a diagnosis of exclusion. Other causes of chronic cough must be ruled out including heart failure, heartworm disease, pneumonia, lung tumors, collapsing trachea, and interstitial lung diseases.
Diagnostic Workup
High-YieldNormal BAL cytology in dogs: approximately 80% macrophages, 7% lymphocytes, 5% neutrophils, 6% eosinophils. In chronic bronchitis, expect neutrophilic inflammation (greater than 8% neutrophils). In eosinophilic bronchopneumopathy (EBP), expect eosinophilic inflammation (greater than 10% eosinophils). Dogs with EBP are systemically unwell, unlike dogs with chronic bronchitis.
| Drug |
Initial Dose |
Maintenance |
Notes |
| Prednisone/Prednisolone |
0.5-1 mg/kg PO q12h x 1 week, then 0.5 mg/kg q12h x 1 week |
Taper to lowest effective dose; goal is alternate-day therapy |
First-line; most effective; watch for PU/PD, polyphagia |
| Fluticasone (Inhaled) |
110-220 mcg q12h via AeroDawg chamber |
Continue q12h; may adjust based on response |
Fewer systemic side effects; requires spacer chamber and training |
| Hydrocodone |
0.22 mg/kg PO q6-12h |
As needed for persistent cough |
Adjunct therapy; use sparingly |
Treatment
Infectious Tracheobronchitis (Kennel Cough)
Uncomplicated Cases
Most cases are self-limiting and resolve within 7-10 days with supportive care:
- Rest, warmth, and proper hygiene
- Use harness instead of collar to reduce tracheal pressure
- Cough suppressants for persistent non-productive cough
- Isolation from other dogs (contagious up to 8 weeks post-recovery)
Complicated Cases (Pneumonia)
- Hospitalization with IV fluids
- Oxygen supplementation if dyspneic
- Broad-spectrum antibiotics based on culture (cephalosporin + fluoroquinolone or aminoglycoside)
- Nebulization therapy
NAVLE TipNEVER give antitussives to a dog with pneumonia! Suppressing the cough prevents clearance of infectious material from the airways and can worsen the condition. Always confirm absence of pneumonia before prescribing cough suppressants.
Chronic Bronchitis
Corticosteroids are the mainstay of therapy for chronic bronchitis. The goal is to reduce airway inflammation, decrease mucus production, and control cough.
Environmental Management
- Eliminate exposure to cigarette smoke and irritants
- Weight management for obese patients
- Use harness instead of collar
- Avoid extreme temperature changes
- Humidification may help loosen secretions
High-YieldAntibiotics are NOT indicated for chronic bronchitis unless there is cytologic evidence of septic inflammation (intracellular bacteria). A positive culture alone does not indicate infection, as bacterial colonization (less than 1.7 x 10^3 CFU/mL) is common without clinical significance.
| Vaccine |
Route and Protocol |
Notes |
| Bordetella (Intranasal) |
One dose as early as 3-4 weeks; 4 days for immunity; annual or q6 months for high-risk |
Stimulates local mucosal immunity; preferred for rapid protection |
| Bordetella (Injectable) |
Two doses 2-4 weeks apart; booster annually |
Subunit vaccine; systemic immunity; may cause local reaction |
| DHPP (Core) |
Puppy series at 6-8 weeks, repeat q3-4 weeks until 16 weeks; booster at 1 year, then q3 years |
Includes distemper, adenovirus-2 (protects against CAV-1 and CAV-2), parainfluenza, parvovirus |
| Canine Influenza |
Two doses 2-4 weeks apart; annual booster |
Bivalent (H3N8/H3N2); recommended for high-risk dogs |
Prevention
Vaccination for Infectious Tracheobronchitis
NAVLE TipVaccination does not completely prevent infection but significantly reduces severity of disease and shedding duration. Intranasal Bordetella vaccine provides local immunity more rapidly (4 days) compared to injectable vaccines (2 weeks). The Bordetella vaccine is considered non-core but is highly recommended for at-risk dogs.
| Infectious Tracheobronchitis |
Chronic Bronchitis |
| Uncomplicated: Excellent; self-limiting in 7-10 days
Complicated: Guarded if pneumonia develops; can be life-threatening in puppies |
Guarded: Chronic progressive disease with relapsing course
Irreversible airway changes; lifelong management usually required
Goal: Reduce cough by greater than 50%
Can progress to bronchiectasis or cor pulmonale |
Prognosis
Memory Aids
"KENNEL" - Remember Kennel Cough Features
- Keeps coughing (dry, honking cough)
- Exposure history (boarding, shelter, dog park)
- No systemic illness (eating, drinking, active)
- Normally self-limiting (7-10 days)
- Ends with gagging or retching
- Likely Bordetella + viral co-infection
"CHRONIC" - Remember Chronic Bronchitis Features
- Cough daily for greater than 2 months
- Harsh, dry, non-productive cough
- Radiographs: bronchial pattern (donuts/tramlines)
- Older, small-breed dogs
- Neutrophilic inflammation on BAL
- Irreversible changes; lifelong management
- Corticosteroids are first-line treatment