Bronchitis in dogs

Overview

Acute and chronic bronchitis

Inflammation can start suddenly or persist. Concurrent tracheal inflammation is called tracheobronchitis. Chronic bronchitis requires at least two months of coughing by definition. Signs can warrant investigation before this threshold.

A UK referral study identified chronic bronchitis in 80 of 329 dogs with persistent cough, or 24.3%. Tracheal or bronchial collapse was more common at 30.7%. Infectious kennel cough spreads readily among closely housed dogs.

A Japanese study found chronic bronchitis in 142 dogs, or 34.1% of those referred for tracheal or bronchial disease. Conditions can coexist, such as chronic inflammation and bronchial collapse.

Causes

Inflammation, mucus and irritation

Chronic bronchitis involves persistent wall inflammation and excess mucus. Impaired mucus-clearing cilia can leave secretions in bronchi. Structural changes can sustain inflammation by disrupting mucus transport. Coughing helps remove mucus. Inflammation can occur without bacterial infection. Chemical fumes can irritate airways and cause tracheobronchitis. Inhaled foreign bodies can also predispose to bronchitis.

Infections and other cough causes

Viruses and bacteria can cause kennel cough. Canine parainfluenza is one associated virus. Several pathogens can coexist. Bordetella bronchiseptica can cause bacterial bronchitis. Lungworm can mimic chronic bronchitis. Crenosoma vulpis, the fox lungworm, has been identified in pet dogs. Other causes include lung tumours and eosinophilic lung disease.

Swallowing disorders can predispose to irritating material entering the lungs.

Risk factors

Middle-aged and older dogs are most commonly affected. Small dogs are frequently diagnosed, but large breeds can also develop disease. Median age in the Japanese referral study was 120 months. Toy Poodles had a diagnosis odds ratio of 2.37 in that population. Miniature Dachshunds were also overrepresented. In the UK persistent-cough study, weight did not predict chronic bronchitis after other investigated factors were considered.

Sudden weather or environmental changes can worsen chronic signs, particularly in older dogs. Crowding previously unexposed dogs increases infectious respiratory disease risk.

Typical symptoms

Repeated coughing is the main visible sign. Its sound does not always reveal mucus because dogs may swallow secretions.

• Coughing bouts after rest.
• Coughing when starting activity or walks.
• Worsening with environmental changes.
• Increased exercise fatigue with persistent cough.
• Wheezing or crackling breathing sounds.

Acute kennel cough can cause gagging after dry cough. Fever with tiredness or inappetence can suggest pneumonia. Purulent nasal discharge is one possible bacterial infection sign.

The worst acute tracheobronchitis signs can ease within two to three days despite weeks of coughing. Typical kennel cough usually improves during the first five days. Coughing blood with persistent cough warrants investigation of other diseases such as tumours.

Complications and consequences

Bronchiectasis and collapse

Persistent inflammation can accompany permanent bronchial dilation, or bronchiectasis. Bronchomalacia causes some bronchi to collapse during breathing. Mucus can plug dilated bronchi and obstruct airflow. Bacterial infection can accompany bronchiectasis.

Inflammation can spread into lung tissue as pneumonia. Severe chronic disease can impair blood oxygenation.

Bronchoscopy identified mucus plugs in 41 of 86 dogs with bronchiectasis, or 48%. Severe bronchomalacia was associated with shorter survival after accounting for age and pulmonary pressure. Follow-up identified pneumonia or other parenchymal inflammation in 25 of 71 bronchomalacia dogs, or 35.2%. A study from northern Europe of 47 chronically hypoxic dogs included 13 with chronic bronchitis.

Diagnosis at the vet

Examination and chest imaging

The vet listens over the trachea and chest. Chest X-rays seek changes explaining persistent cough. They also assess heart size and possible cardiac causes. Bronchial walls can appear thickened. X-rays can nevertheless be normal despite inflammatory cells in lavage. Comparing inhalation and exhalation views can reveal collapse. CT maps affected lung regions.

Endoscopy, lavage and bacterial findings

Bronchoscopy shows bronchial lining and abnormalities. A small brush can collect lining cells during it. Lavage assesses inflammatory cell types. Intracellular bacteria support active infection. Culture helps select antimicrobials. PCR can sometimes seek Bordetella or Mycoplasma in lavage. Mycoplasma detection can occasionally reflect oral contamination. Low growth without intracellular bacteria can reflect normal airway flora. Lavage and brush findings may differ.

Baermann faecal testing can seek fox lungworm. Arterial oxygen can be measured with suspected hypoxia. CT found bronchiectasis in all 34 selected dogs undergoing it in one study. X-rays showed it in 50 of 83 dogs, or 60%, in the same study.

Blood inflammatory markers

A study from northern Europe found median C-reactive protein, or CRP, of 13 mg/l in chronic bronchitis. Bacterial pneumonia had a median of 121 mg/l. Bacterial tracheobronchitis had a median of 23 mg/l in that inflammatory marker comparison. Raised CRP can therefore support suspected bacterial pneumonia alongside other findings. Another comparison from northern Europe found high-sensitivity CRP did not distinguish bacterial bronchitis from other chronic cough causes.

Treatment

Controlling persistent inflammation

Treatment depends on bacterial infection or another treatable underlying disease. Corticosteroids can reduce chronic bronchial inflammation. Inhaled fluticasone can treat persistent cough from inflammatory airway disease. Corticosteroids can increase drinking and urination. Appetite can also increase. Long-term use can have systemic adverse effects. Signs may recur if anti-inflammatory treatment stops.

A fluticasone study followed cough in 32 dogs. Among those undergoing bronchoscopy, 88% had both inflammatory disease and collapse. Mean quality-of-life symptom scores fell from 28.1 to 11.3. Cough severity improved within two weeks of follow-up. It did not disappear completely in every dog. Reduced coughing during chronic inflammation treatment does not necessarily mean structural recovery.

Bacterial infection and symptom relief

Antibiotics treat confirmed or strongly suspected bacterial infection. Medication can change according to susceptibility results. Some bacterial infections resolve after one antimicrobial course. Suspected recurrence may warrant sampling before another medication decision. Treating underlying inflammation can reduce secondary bacterial bronchitis recurrence. Fox lungworm requires an effective antiparasitic.

A cough suppressant may be considered for persistent dry cough. Need is assessed particularly carefully with bronchiectasis. Productive coughing clears secretions, so do not give suppressants on your own initiative. A small eight-dog study found reduced cough with maropitant. Lavage inflammatory cell proportions did not change significantly.

Prevention

Reducing smoke exposure avoids one irritant. Poor indoor air can increase mucosal irritation in dogs with existing disease. Kennel cough vaccines protect against some infectious causes. Vaccination does not replace investigation of persistent cough. Consider lung parasites particularly in imported or travelled dogs.

A small study of 20 dogs with respiratory disease identified cellular changes associated with air pollutants. Vaccinated dogs can still get kennel cough because several pathogens can coexist.

Read about dog vaccinations.

Important for dog owners

Record how often your dog coughs and how long each individual coughing bout lasts. Make a note of whether coughing is worst after rest or when your dog starts moving. Tell the vet if nasal discharge appears alongside coughing or your dog loses their appetite. If your dog receives corticosteroids, also monitor how much they drink and urinate. Keep your coughing dog away from other dogs if infectious kennel cough is suspected.

Record severity and daily impact when assessing treatment. Daily function matters because response includes quality of life as well as symptoms.

Frequently asked questions

When is a cough chronic?

A cough in a dog is defined as chronic once it has continued for at least eight weeks. Several different diseases can be responsible for a persistent cough. The vet assesses, for example, whether the signs fit bronchial inflammation or collapse of the airways.

Is chronic bronchitis the same as kennel cough?

Kennel cough is infectious respiratory disease caused by viruses or bacteria. Chronic bronchitis means longstanding bronchial inflammation. Bacteria can accompany it, but inflammation can persist without them. Examination of a bronchial lavage sample can establish the type of inflammation present.

Do normal X-rays rule out bronchitis?

The bronchi can be inflamed even when no abnormalities are visible on X-rays. A lavage sample can show which inflammatory cells are present in the bronchi. Bronchoscopy can also help the vet identify changes in the structure of the airways. CT can establish how extensively these changes affect the lungs.

Does bronchitis always need antibiotics?

Antibiotics are used for bacterial infection following assessment by the vet. Bacterial culture and susceptibility testing of an airway sample can guide the choice of medicine. Chronic inflammation without bacterial evidence may be treated with corticosteroids.

Why can coughing persist despite treatment?

Bronchial inflammation and the associated excess mucus production can keep a dog coughing. If permanent dilation has developed in the bronchi, controlling inflammation alone does not reverse it. Recurring symptoms may sometimes require another lavage sample and bacterial culture.