Bordetella bronchiseptica is a bacterial species that infects the respiratory tract of dogs, cats, rabbits, pigs, and other mammals. It’s the primary culprit behind kennel cough in dogs and a common cause of upper respiratory infections in cats, especially in shelters and breeding facilities. Unlike its close relative Bordetella pertussis, which causes whooping cough exclusively in humans, B. bronchiseptica has a broad host range and can jump between animal species.
How It Infects the Airways
B. bronchiseptica is a small, rod-shaped bacterium that targets the ciliated lining of the upper respiratory tract. Cilia are the tiny, hair-like structures that sweep mucus and debris out of the airways. The bacterium latches onto these cilia using multiple adhesion molecules, essentially anchoring itself to the airway surface so it can’t be cleared out by normal defenses.
Once attached, the bacterium produces toxins that disrupt normal cell function. One key toxin hijacks the cell’s energy system, causing an uncontrolled buildup of a signaling molecule called cyclic AMP inside host cells. This effectively paralyzes the immune cells that would normally fight off the infection. The bacterium uses several attachment proteins in a redundant system, meaning that even if one mechanism fails, others can compensate. This redundancy makes B. bronchiseptica a particularly persistent colonizer.
Kennel Cough in Dogs
The hallmark of B. bronchiseptica infection in dogs is a harsh, dry cough often described as sounding like a “goose honk,” sometimes followed by retching or gagging. Symptoms typically appear 5 to 10 days after exposure, which usually happens in places where dogs are housed closely together: boarding kennels, dog parks, grooming facilities, and shelters. The cough is so sensitive that even light pressure on the throat can trigger it.
Most cases are mild and self-limiting. The worst of the coughing usually fades within the first 5 days, though the illness can linger for 10 to 20 days total. In some dogs, particularly puppies or those with weakened immune systems, the infection can progress to bronchopneumonia. Warning signs of this more serious form include fever, thick nasal discharge, loss of appetite, lethargy, and a wet, productive cough.
It’s worth noting that kennel cough is often a mixed infection. B. bronchiseptica frequently works alongside viruses like canine parainfluenza or canine adenovirus, which damage the airway lining first and make bacterial colonization easier.
Infection in Cats
Cats are also susceptible, particularly those in high-density environments like shelters and catteries. Symptoms range from mild sneezing, coughing, and eye discharge to severe lower respiratory infections. Young kittens face the greatest risk. In serious cases, cats can develop difficulty breathing, blue-tinged gums (a sign of oxygen deprivation), and the infection can be fatal. Older cats generally fare better, though severe disease isn’t limited to kittens. Infected dogs can spread the bacterium to cats living in the same household.
How It’s Diagnosed
Veterinarians often diagnose kennel cough based on symptoms and exposure history alone. When laboratory confirmation is needed, two main methods are available: bacterial culture and PCR testing. PCR, which detects the bacterium’s genetic material, picks up infections that culture misses. In one study of dogs with persistent respiratory signs, 40% of PCR-positive cases had negative culture results. Combining both tests gives the most reliable picture, since culture alone would have missed a significant number of infected animals.
Treatment
Mild cases in otherwise healthy dogs often resolve without antibiotics, with rest and supportive care (keeping the air humidified, using a harness instead of a collar to avoid throat pressure). When antibiotics are needed, particularly for more severe infections or vulnerable animals, the choice requires some care. B. bronchiseptica has natural resistance to common antibiotic classes including penicillin-type drugs and certain other widely used options. It also carries resistance genes on mobile genetic elements called plasmids, which can be transferred between bacteria, making resistance patterns somewhat unpredictable.
Reliable data on which antibiotics work best is surprisingly limited, and standardized testing guidelines for this bacterium are still catching up. Your veterinarian may recommend culture and sensitivity testing for infections that don’t respond to initial treatment.
Vaccination Options
Three types of B. bronchiseptica vaccines are available for dogs: intranasal (squirted into the nose), oral (given by mouth), and injectable. The intranasal and oral versions have a major practical advantage: they can provide protection within 7 days of a single dose. In a controlled study, both oral and intranasal vaccines prevented disease in 100% of vaccinated dogs when challenged with live bacteria one week after vaccination, compared to an 89% infection rate in unvaccinated dogs.
Injectable vaccines require two doses given several weeks apart, so full immunity takes longer to develop. This makes them less useful for last-minute protection before boarding or travel. The tradeoff is that some dogs tolerate the injection better than having a vaccine administered into their nose, which can occasionally cause mild sneezing or nasal discharge for a day or two.
Most boarding facilities, doggy daycares, and grooming salons require proof of Bordetella vaccination. If your dog regularly interacts with other dogs, keeping this vaccine current significantly reduces the risk of infection.
How It Spreads and How Long It Survives
B. bronchiseptica spreads through respiratory droplets (coughing, sneezing, nose-to-nose contact) and through contaminated objects like shared water bowls, toys, and kennel surfaces. In respiratory secretions, the bacterium survives only a few hours. But in the right conditions, it’s hardier than you might expect: it can persist in water for up to 24 weeks at cool temperatures and survive in soil for 45 days.
Standard disinfectants kill it readily. Dilute bleach solutions, 70% alcohol, and common veterinary disinfectants are all effective. Regular cleaning of shared spaces and equipment in multi-dog environments is one of the simplest ways to reduce transmission.
Can Humans Get Infected?
Human infection with B. bronchiseptica is rare but documented. A literature review identified 23 reported cases, and nearly all occurred in people with severely compromised immune systems, including those with blood cancers like chronic lymphocytic leukemia and Hodgkin’s disease, or those undergoing treatments that suppress immune function. Most human cases involved respiratory infections. For healthy individuals, the risk from contact with an infected pet is extremely low.
How It Differs From Whooping Cough Bacteria
B. bronchiseptica and B. pertussis (the whooping cough pathogen) are close genetic relatives. Their key adhesion proteins share about 90% of their genetic sequence and appear to be functionally interchangeable. The critical difference is host range: B. pertussis is strictly a human pathogen, while B. bronchiseptica infects a wide variety of mammals but rarely causes disease in people. Despite their similarity, structural differences in their surface proteins help explain why each species is adapted to its preferred hosts.