Canine infectious respiratory disease complex

What it is

Canine infectious respiratory disease complex (CIRDC), commonly called kennel cough or infectious tracheobronchitis, is an acute, highly contagious infection of the airways. It is multifactorial: several pathogens, often in combination, damage the respiratory epithelium and the mucociliary clearance. The main agents are Bordetella bronchiseptica, canine parainfluenza virus, canine adenovirus type 2, canine respiratory coronavirus, canine influenza virus (H3N8, H3N2), canine herpesvirus, Mycoplasma cynos and Streptococcus equi subsp. zooepidemicus; canine distemper virus can begin with similar signs. Transmission is by aerosols, direct contact and fomites, and is favoured where many dogs gather.

Who it affects

Dogs of any age and breed, especially those in shelters, boarding kennels, day-care centres, shows and training classes. Puppies, old dogs, brachycephalic breeds and immunocompromised dogs are more likely to develop pneumonia.

Anatomy involved

• Trachea and bronchi: the main site of disease; inflammation of the mucosa causes the cough.
• Larynx and upper airways: rhinitis and laryngitis with nasal and ocular discharge.
• Lungs: secondary bacterial bronchopneumonia, usually cranioventral, in complicated cases.

Clinical signs

After an incubation of a few days to about a week: a sudden, loud, harsh cough, often followed by gagging or retching that owners mistake for vomiting, easily triggered by tracheal palpation or a collar. Nasal and ocular discharge and sneezing. Most dogs stay bright and eat normally, and signs resolve in one to three weeks. Fever, lethargy, anorexia, tachypnoea and dyspnoea suggest pneumonia.

Diagnosis

• Clinical: compatible signs and a history of contact with other dogs are usually enough in uncomplicated cases.
• Thoracic radiographs: in dogs with systemic signs, to look for a cranioventral alveolar pattern.
• PCR panels on nasal, oropharyngeal or deep pharyngeal swabs: identify the agents involved, useful in outbreaks and shelters.
• Airway lavage with culture and sensitivity: in pneumonia or refractory cases.

Treatment

Uncomplicated cases resolve on their own; rest, a harness instead of a collar and isolation from other dogs are recommended. Antitussives can be used when the cough is unproductive and there is no pneumonia. Antibiotics active against Bordetella and Mycoplasma (doxycycline is a common first choice) are reserved for dogs with fever, purulent discharge or suspected pneumonia. Pneumonia may need hospitalisation, oxygen, fluids and nebulisation. Prevention relies on vaccination (parenteral and mucosal vaccines against Bordetella, parainfluenza, adenovirus and, where relevant, influenza), ventilation and hygiene in kennels.