By Dial A Vet Veterinary Team
Kennel cough is not one disease with one cause. It is a syndrome, and the same honking cough can come from a single bacterium, a virus, or several germs working together. That matters because it explains why a fully vaccinated dog can still catch it, why some cases fade in a week while others turn into pneumonia, and why your vet may not reach for antibiotics straight away. Knowing the main culprits helps you make sense of vaccine advice and of what your vet tells you.
Key takeaways
- Bordetella bronchiseptica is the best-known bacterial cause, but viruses such as canine parainfluenza and canine adenovirus type 2 are common too.
- Many cases involve more than one germ at once. A virus often damages the airway first and bacteria take advantage.
- The C5 vaccine covers Bordetella, parainfluenza and adenovirus, but not every cause.
- Canine influenza, a major cause overseas, is not considered established in Australia.
- Stress, crowding, poor ventilation and existing airway disease all make infection more likely and more severe.
The main causes
Bordetella bronchiseptica
This bacterium sticks to the cilia, the microscopic hairs lining the windpipe, and stops them working. Without that clearing action, mucus and debris build up and the airway becomes inflamed. Bordetella is very contagious and can survive for a time on bowls, bedding and hands. Some dogs keep shedding it for weeks after they look well.
Canine parainfluenza virus
One of the most frequent viral causes. On its own it usually produces a short, mild illness, but it damages the airway lining and makes it easier for bacteria to take hold.
Canine adenovirus type 2
A respiratory virus related to the virus that causes infectious canine hepatitis. Vaccines against adenovirus protect against both.
Other contributors
- Mycoplasma species: small bacteria often found alongside other infections.
- Canine respiratory coronavirus: different from the coronavirus that causes COVID-19 in people, and not covered by routine vaccines.
- Canine herpesvirus: occasionally involved, and more serious in very young puppies.
- Canine distemper virus: can start with cough and nasal discharge before more serious signs appear. It is now uncommon in well-vaccinated populations, which is a good reason to keep C5 boosters current.
Overseas, canine influenza (H3N8 and H3N2 strains) is a significant cause of respiratory outbreaks. It is not considered established in Australia, and any suspicion would be treated seriously by authorities.
Why some dogs get sicker than others
Exposure is only part of the story. Risk is higher in dogs that are:
- Young puppies or seniors
- Brachycephalic (flat-faced) breeds such as pugs, bulldogs and French bulldogs
- Living with tracheal collapse, chronic bronchitis or heart disease
- Stressed by boarding, travel or rehoming
- Housed in crowded, poorly ventilated spaces
Signs
The typical dog has a dry, goose-honk cough, sometimes followed by gagging up white froth, and is otherwise bright. A soft or moist cough, fever, lethargy, thick coloured nasal discharge or poor appetite suggests the infection may be spreading into the lungs. If your dog has these signs, read our guide to pneumonia in dogs and contact your vet.
When to see a vet
Emergency now: laboured breathing, blue or grey gums, collapse, or open-mouth breathing at rest.
Same day: a coughing puppy, senior, flat-faced dog or dog with heart disease, or any dog that is lethargic, feverish or off food.
Can wait a few days: a bright, eating adult with a mild cough that is steady or improving. Arrange a check if it is not clearly better within a week.
What to do
- Keep your dog home and away from other dogs.
- Wash bowls, bedding and toys, and wash your hands after handling your dog.
- Use a harness instead of a collar.
- Let your boarding kennel, groomer or daycare know so they can warn other owners.
- Do not give human cold or cough medicines.
How vets work out the cause
In a typical mild case, identifying the exact germ does not change much, so vets usually diagnose based on history and examination. When a dog is very unwell, part of an outbreak, or not responding as expected, your vet may recommend a respiratory PCR panel from a nasal or throat swab, chest x-rays, or sampling from deeper in the airways. This helps guide treatment choices, including whether an antibiotic is likely to help. Viruses do not respond to antibiotics, so they are used thoughtfully.
Prevention and vaccines
In Australia the C5 vaccine combines the core C3 components (distemper, hepatitis and parvovirus) with parainfluenza and Bordetella. Bordetella protection is available as an intranasal or oral vaccine as well as an injectable, and boarding kennels usually require it to be current. Vaccination will not block every infection, but it reduces the severity and the amount of shedding. Our article on the Bordetella vaccine has more detail on how it is given.
FAQ
If Bordetella is bacterial, why did my vet not prescribe antibiotics?
Many mild cases settle on their own, and some are viral. Your vet weighs your dog's signs, age and risk factors before deciding whether antibiotics are needed.
Can a vaccinated dog spread kennel cough?
Yes. Vaccinated dogs can still be infected with causes not covered by the vaccine, and can shed Bordetella with few signs.
Is there a test that tells which germ my dog has?
Yes, PCR panels from swabs can identify several common respiratory germs. They are most useful in severe cases or outbreaks.
Can cats catch Bordetella from dogs?
It is possible, especially in multi-pet homes or shelters, though cats are less commonly affected.
Talk with a vet
If you want help deciding whether your dog's cough needs a clinic visit, or advice on vaccines before boarding, a Dial A Vet consult is a quick place to start. Breathing difficulty or collapse is an emergency, so head to your nearest emergency vet in person.
References
- Merck Veterinary Manual: Canine Infectious Respiratory Disease Complex
- WSAVA Guidelines for the Vaccination of Dogs and Cats
- Australian Veterinary Association: Vaccination of dogs and cats
- Animal Health Australia: Emergency animal disease information
Disclaimer: Educational only. This page does not replace an examination or advice from your own veterinarian. Contact your vet if your dog is coughing and you are concerned.