Bordetella in Dogs and Cats: Beyond Kennel Cough

Bordetella bronchiseptica is a highly contagious, Gram-negative bacterium that colonises the respiratory tract of dogs, cats, and occasionally other mammals. It is the single most common bacterial agent involved in canine infectious respiratory disease complex (CIRDC) — the condition most pet owners know as "kennel cough." However, reducing Bordetella to a simple kennel cough bug dramatically underestimates its clinical significance. In puppies, immunocompromised dogs, brachycephalic breeds, and cats, Bordetella can cause serious lower respiratory disease, including bronchopneumonia that may be life-threatening.

Dr. Sarah Chen, DVM: "Bordetella is not just a nuisance cough that goes away on its own. In young puppies, elderly dogs, flat-faced breeds, and especially in cats — where the infection is often overlooked — Bordetella can progress to pneumonia rapidly. Early recognition and appropriate antibiotic therapy make a significant difference in outcomes."

Bordetella bronchiseptica belongs to the same genus as Bordetella pertussis, the bacterium responsible for whooping cough in humans. Like its human counterpart, B. bronchiseptica has evolved sophisticated mechanisms to evade the host immune system. It produces several virulence factors, including:

• Filamentous haemagglutinin (FHA): Allows the bacterium to adhere tightly to the cilia (tiny hair-like structures) lining the respiratory tract.
• Tracheal cytotoxin: Directly damages ciliated epithelial cells, paralysing the mucociliary escalator — the respiratory tract's primary defence mechanism for clearing debris and pathogens.
• Adenylate cyclase toxin: Inhibits immune cell function, reducing the effectiveness of neutrophils and macrophages that would otherwise destroy the bacteria.
• Dermonecrotic toxin: Causes tissue damage and inflammation, contributing to the severity of clinical signs.

By damaging the respiratory epithelium and suppressing local immunity, Bordetella not only causes disease itself but also creates an environment that is highly susceptible to secondary infections from other bacteria and viruses. This is why CIRDC is often a polymicrobial infection rather than a single-pathogen disease.

Bordetella bronchiseptica is remarkably efficient at spreading between animals, which is why outbreaks are so common in environments where dogs or cats are housed together.

Routes of Transmission

• Aerosolised respiratory droplets: The primary route. When an infected dog coughs or sneezes, Bordetella-laden droplets can travel up to 2 metres and be inhaled by nearby animals. A single coughing episode can release thousands of infectious particles into the air.
• Direct nose-to-nose contact: Close contact during greeting, play, or mutual grooming transmits bacteria efficiently from nasal secretions.
• Fomites (contaminated surfaces): Bordetella can survive on surfaces — water bowls, toys, bedding, kennel walls, and human hands — for several hours to days, depending on environmental conditions. This is why thorough disinfection of boarding facilities is essential.
• Cross-species transmission: Bordetella bronchiseptica can transmit between dogs and cats, and occasionally to rabbits, guinea pigs, and pigs. In multi-species households, an infected dog can transmit the bacterium to a cat and vice versa.

High-Risk Environments

Any environment with a high density of animals and frequent turnover creates ideal conditions for Bordetella transmission. These include:

• Boarding kennels and catteries — the classic "kennel cough" scenario
• Dog daycare facilities — extended close contact during play
• Animal shelters and rescue centres — stress plus overcrowding
• Dog shows and competitions — dogs from diverse backgrounds congregating
• Training classes — especially puppy socialisation groups
• Veterinary waiting rooms — where sick animals are concentrated
• Dog parks — uncontrolled interactions with unknown vaccination status

Populations Most Vulnerable to Severe Disease

While healthy adult dogs typically develop mild, self-limiting disease, certain populations are at risk of developing serious complications:

• Puppies under 6 months: Immature immune systems cannot contain the infection as effectively
• Senior dogs: Declining immune function and often concurrent health issues
• Brachycephalic breeds (Bulldogs, Pugs, French Bulldogs): Compromised upper airway anatomy makes them more susceptible to respiratory infections and more likely to develop pneumonia
• Immunosuppressed animals: Those on chemotherapy, long-term steroids, or with concurrent diseases
• Cats: Often overlooked as Bordetella hosts — see our cat vaccination guide for feline-specific prevention strategies

The clinical presentation of Bordetella infection differs significantly between dogs and cats, which is one reason feline Bordetella is frequently misdiagnosed or missed entirely.

Bordetella in Dogs: The Classic Kennel Cough Presentation

In otherwise healthy adult dogs, Bordetella typically causes an upper respiratory infection — infectious tracheobronchitis — with the following hallmark signs:

• Harsh, dry, "honking" cough: The signature symptom. Often described as sounding like a goose honk, this cough is triggered by tracheal sensitivity. It may be followed by gagging or retching, which owners sometimes mistake for vomiting.
• Coughing paroxysms: Bouts of intense coughing, particularly after excitement, exercise, pulling on a lead, or changes in air temperature (e.g., going from warm indoors to cold outside).
• Clear nasal discharge: Which may become mucopurulent (thick, yellow-green) if secondary bacterial infection develops.
• Mild lethargy: Some dogs remain otherwise bright and active; others become subdued.
• Normal or mildly reduced appetite: Most dogs continue eating well.

In uncomplicated cases, symptoms resolve within 7–14 days with or without treatment. However, complicated cases — particularly in vulnerable populations — can progress to:

• Productive (wet) cough: Indicating lower respiratory involvement
• High fever (above 39.5°C / 103.1°F): Suggesting pneumonia
• Difficulty breathing: Increased respiratory rate and effort
• Complete loss of appetite and severe lethargy: Warning signs of systemic illness

Bordetella in Cats: A Different Disease

Bordetella in cats presents quite differently from the classic kennel cough seen in dogs. Feline Bordetella infection more closely resembles upper respiratory infection (cat flu) and is often misattributed to viral causes. Key feline symptoms include:

• Sneezing: Often the most prominent sign, sometimes violent and paroxysmal
• Nasal discharge: Typically mucopurulent from the outset
• Ocular discharge and conjunctivitis: Watery to purulent eye discharge
• Fever and lethargy: More common in cats than dogs
• Submandibular lymphadenopathy: Enlarged lymph nodes under the jaw
• Cough: Less common in cats than dogs, but when present, it is a significant finding that should prompt investigation for Bordetella

Kittens are at the greatest risk of severe disease, and Bordetella can be fatal in young kittens if not treated promptly. If your cat or kitten shows respiratory signs, consult a veterinarian — our vet visit guide can help you assess urgency.

Accurate diagnosis of Bordetella is important because, unlike viral respiratory infections, bacterial infections respond to targeted antibiotic therapy. However, in practice, many cases of kennel cough are treated empirically based on clinical signs and exposure history.

Diagnostic Approaches

• Clinical diagnosis: In dogs with a characteristic honking cough and a history of recent boarding, daycare, or exposure to other dogs, a presumptive diagnosis of CIRDC (including Bordetella) is often made without further testing. This is appropriate for mild, uncomplicated cases.
• PCR (polymerase chain reaction): Swabs from the oropharynx or transtracheal wash samples can be tested by PCR for Bordetella DNA. This is the most sensitive and specific test available and is particularly valuable when distinguishing Bordetella from viral pathogens, when an outbreak investigation is needed, or when a cat presents with respiratory signs of unclear origin.
• Bacterial culture and sensitivity: Respiratory samples can be cultured to identify Bordetella and determine antibiotic sensitivity. While slower than PCR (results take 3–5 days), culture and sensitivity is invaluable for guiding antibiotic choice in resistant or recurrent infections.
• Chest radiographs (X-rays): Indicated when pneumonia is suspected — persistent fever, productive cough, difficulty breathing, or worsening despite treatment. Radiographs can reveal alveolar patterns, consolidation, or bronchial thickening consistent with bronchopneumonia.

Treatment Strategies

Mild, uncomplicated kennel cough in healthy adult dogs:

• Rest and isolation: Reduce exercise and keep the dog away from other dogs for at least 14 days to limit transmission. Use a harness instead of a collar to avoid tracheal pressure.
• Cough suppressants: In some cases, veterinarians may prescribe a cough suppressant (such as butorphanol or hydrocodone) to provide comfort, particularly if coughing is severe enough to disrupt sleep or cause retching.
• Humidified air: Running a humidifier or placing the dog in a steam-filled bathroom can soothe irritated airways.
• Monitoring: Most cases resolve within 7–14 days. If symptoms worsen, persist beyond 2 weeks, or if fever develops, veterinary reassessment is essential.

Moderate-to-severe cases and all feline infections:

• Antibiotic therapy: Doxycycline is the first-line antibiotic for Bordetella in both dogs and cats. It achieves excellent concentrations in respiratory tissues and is effective against most Bordetella strains. A typical course is 10–14 days. Alternatives include amoxicillin-clavulanate, azithromycin, or fluoroquinolones (enrofloxacin — used cautiously in cats due to risk of retinal toxicity at high doses).
• Anti-inflammatory therapy: NSAIDs may reduce airway inflammation and improve comfort.
• Nebulisation and coupage: For pneumonia cases, nebulisation with sterile saline helps loosen airway secretions, and gentle chest percussion (coupage) helps mobilise mucus.
• Supportive care: IV fluids, oxygen therapy, and nutritional support may be needed for severe pneumonia cases requiring hospitalisation.

Prevention of Bordetella infection relies on two pillars: vaccination and environmental management. Neither alone is sufficient, but together they dramatically reduce the risk and severity of infection.

Bordetella Vaccination for Dogs

The Bordetella vaccine for dogs is classified as a non-core (lifestyle) vaccine by most veterinary guidelines — meaning it is recommended based on risk rather than given to every dog. However, in practice, it is one of the most commonly administered vaccines because so many dogs are exposed to high-risk environments. Bordetella vaccination is typically required for:

• Boarding kennels
• Dog daycare
• Grooming facilities
• Training classes and puppy socialisation
• Dog shows and competitions

Three vaccine formats are available:

• Intranasal (IN): Administered as drops into the nostrils. Provides rapid local immunity (within 48–72 hours) at the site where the bacterium first colonises. This is the most commonly used form and is particularly useful when rapid protection is needed before boarding.
• Oral: Administered as a liquid into the cheek pouch. Similar onset and efficacy to intranasal, with the advantage of being easier to administer in dogs that resist nasal administration.
• Injectable (subcutaneous): Provides systemic immunity but takes 10–14 days for full protection. Does not provide the same level of local mucosal immunity as intranasal or oral routes. Requires a two-dose primary series in puppies.

Vaccination schedules vary by product, but a common protocol is:

• First dose at 8 weeks of age (intranasal or oral can be given as a single dose)
• Booster annually, or every 6 months for dogs in very high-risk environments

Bordetella Vaccination for Cats

An intranasal Bordetella vaccine is available for cats and is recommended for those in high-risk environments — shelters, catteries, and multi-cat households with a history of respiratory disease. Consult our cat vaccination schedule guide for details on incorporating Bordetella vaccination into your cat's health plan.

Important Limitations of Vaccination

Bordetella vaccination does not prevent infection entirely. Like the human influenza vaccine, it reduces the severity and duration of illness and decreases viral shedding, but vaccinated dogs and cats can still become infected and show mild symptoms. Additionally, CIRDC involves multiple pathogens — vaccination against Bordetella alone does not protect against all causes of kennel cough. A comprehensive preventative care schedule that includes parainfluenza, canine influenza (where available), and adenovirus-2 vaccination provides broader protection.

If your dog or cat has been diagnosed with Bordetella, prompt action can speed recovery and protect other animals in your household and community.

Isolation and Quarantine

Bordetella is highly contagious, and infected animals should be isolated from other dogs and cats for at least 14 days after symptoms resolve. Even after clinical signs disappear, animals can continue shedding the bacterium for several weeks. During isolation:

• Keep the infected pet in a separate room with good ventilation
• Use separate food bowls, water bowls, bedding, and toys
• Wash hands thoroughly after handling the infected animal before touching other pets
• Change clothing if you have been in close contact with the infected pet before interacting with other animals
• Avoid dog parks, daycare, boarding, and training classes until your veterinarian confirms the infection has resolved

Environmental Decontamination

Bordetella bronchiseptica is susceptible to most common disinfectants, but thorough cleaning is essential. Recommended steps include:

• Clean all surfaces with an accelerated hydrogen peroxide disinfectant (such as Rescue/Accel) or dilute bleach solution (1:32). Pay particular attention to food and water bowls, flooring, kennel walls, and door handles.
• Wash all bedding and soft toys in hot water (at least 60°C / 140°F) with detergent.
• Replace items that cannot be disinfected, such as heavily soiled plush toys or porous materials.
• Ventilate the space: Good airflow reduces the concentration of aerosolised bacteria in indoor environments.

Multi-Pet Household Considerations

If you have multiple dogs or cats, assume all animals in the household have been exposed once one is diagnosed. Monitor all pets closely for respiratory signs. Consult your veterinarian about whether prophylactic antibiotics are warranted for at-risk housemates (puppies, kittens, elderly pets, or immunocompromised animals). Remember that Bordetella can transmit between dogs and cats, so both species need monitoring even if only one appears symptomatic.

Most dogs and cats recover fully from Bordetella infection with appropriate care. The key is to take the infection seriously — especially in vulnerable animals — seek veterinary advice when symptoms are severe or prolonged, and follow through with the full course of any prescribed antibiotics. If you are unsure whether your pet's symptoms warrant a vet visit, our guide to recognising warning signs can help you make that decision with confidence.