Kennel cough is both viral and bacterial. It’s not a single infection but a mix of pathogens that attack a dog’s respiratory tract, often at the same time. Veterinarians call it canine infectious respiratory disease complex (CIRDC) because multiple organisms are usually involved in a single case.
The Pathogens Behind Kennel Cough
At least a dozen different viruses and bacteria can cause or contribute to kennel cough. On the viral side, the most common culprits are canine parainfluenza virus, canine adenovirus type 2, canine respiratory coronavirus, canine influenza virus, and canine pneumovirus. On the bacterial side, the primary player is Bordetella bronchiseptica, along with Mycoplasma species and Streptococcus equi zooepidemicus.
In many cases, a virus weakens the airway lining first, creating an opening for bacteria to move in and make things worse. This is why kennel cough can start as a mild cough and then escalate over several days. A purely viral case tends to be milder and shorter, while a case involving Bordetella or secondary bacterial infection can drag on longer and carry a higher risk of pneumonia.
How These Pathogens Damage the Airways
The viruses involved in kennel cough target cells lining the trachea and bronchi, the large airways leading to the lungs. They replicate inside those cells, killing them and stripping away the protective mucus layer. This is what triggers the hallmark dry, hacking cough that often sounds like a goose honk.
Bordetella bronchiseptica works a bit differently. After a dog inhales or ingests the bacteria, they latch directly onto the cilia, the tiny hair-like structures that sweep debris and mucus out of the airways. The bacteria damage this lining in the trachea and bronchi, and in more advanced cases the infection spreads into the lungs themselves. Because the cilia are compromised, the dog loses its natural ability to clear mucus and pathogens, which is why bacterial involvement often means a more stubborn infection.
Symptoms to Watch For
The classic sign is a persistent dry, hacking cough, sometimes followed by retching or gagging that owners mistake for vomiting. Sneezing and a watery nasal discharge are also common, especially in the early viral stage. Most dogs with uncomplicated kennel cough still eat normally, stay active, and don’t run a fever.
Severe cases look different. If the infection reaches the lungs, you may notice lethargy, loss of appetite, fever, and labored breathing. Puppies, senior dogs, and flat-faced breeds are more vulnerable to this progression.
How It Spreads and How Long It Lasts
Kennel cough spreads through airborne droplets when an infected dog coughs, sneezes, or simply breathes near other dogs. Shared water bowls, toys, and kennel surfaces can also carry the bacteria. The incubation period ranges from 2 to 14 days, so a dog can pick up the infection at a boarding facility or dog park and not show symptoms until well after returning home.
The cough itself typically resolves within one to three weeks in uncomplicated cases. But here’s the important detail for dog owners: dogs infected with Bordetella continue to shed the bacteria for one to three months after infection. That means your dog can appear completely healthy and still be contagious to other dogs for weeks.
How Vets Diagnose It
Most of the time, veterinarians diagnose kennel cough based on the characteristic cough, a physical exam, and a history of exposure to other dogs. Tests exist that can identify each specific pathogen, including PCR panels that detect viral and bacterial DNA from nasal or throat swabs. But unless the vet suspects something more serious like distemper or pneumonia, specific pathogen testing is usually not pursued. The treatment approach is similar regardless of which virus or bacteria started it.
Treatment: When Antibiotics Help and When They Don’t
Because kennel cough is often self-limiting, antibiotics are usually not needed. If the infection is primarily viral, antibiotics won’t do anything at all, since they only work against bacteria. Rest, humidity, and keeping your dog away from other animals are the main strategies for a mild case.
Antibiotics come into play when there’s evidence of bacterial involvement, particularly if the infection has progressed to pneumonia. In those cases, vets ideally select the antibiotic based on a culture and sensitivity test, which identifies exactly which bacteria are present and which drugs will work against them. A typical course lasts 7 to 14 days. Cough suppressants may be used for comfort in mild cases but are not safe for dogs with pneumonia, because coughing helps clear infected fluid from the lungs.
Vaccination Options
Vaccines exist for several of the pathogens involved in kennel cough, though no single vaccine covers every possible cause. The American Animal Hospital Association classifies the parainfluenza vaccine as a core vaccine, meaning all dogs should receive it. Bordetella and canine influenza vaccines are classified as noncore, recommended based on a dog’s lifestyle and risk level. Dogs that regularly visit boarding facilities, doggy daycare, groomers, or dog parks are strong candidates.
The Bordetella vaccine comes in injectable, oral, and intranasal forms. It reduces the severity and duration of illness but doesn’t guarantee complete protection, because so many different organisms can cause the disease. Think of it like a flu shot: it lowers your risk and makes any breakthrough case milder, but it can’t block every possible strain.
Can Humans Catch It?
Bordetella bronchiseptica can, in rare cases, infect humans. It’s an infrequent cause of respiratory illness in people, and the risk is concentrated in immunocompromised individuals, particularly those with HIV or those on immunosuppressive medications. Infections in otherwise healthy people have been reported but are uncommon. The bacteria transmit through aerosols from infected animals, so people with weakened immune systems should avoid close contact with dogs that have active respiratory infections.