Overview

Bordetellosis is a very contagious respiratory infection in dogs caused by the bacterium Bordetella bronchiseptica. Dogs with clinical signs of this infection are commonly referred to as having “kennel cough” or infectious tracheobronchitis. It is one of the organisms involved with canine infectious respiratory disease complex (CIRDC). 

This infection usually affects the upper respiratory tract and is known for its characteristic dry, “honking” cough. While it is usually mild and self-limiting, bordetellosis can sometimes progress to more serious illness.

How are dogs infected with Bordetella?

Modes of transmission:

• Airborne (most common). Through coughing and sneezing, an infected dog can spread bacteria-containing droplets (aerosol) of mucus and saliva onto other dogs in close proximity.
• Direct dog-to-dog contact
• Contact with contaminated surfaces and objects (also known as fomites) including toys, food bowls and even on clothing and hands
• Contact with contaminated water

Dogs of all ages can become infected and develop clinical signs. Dogs most at risk include those in close contact, puppies, unvaccinated dogs, dogs with preexisting respiratory disease, or dogs with other underlying medical conditions who may be immunocompromised. Stress can play a role.

There is increased prevalence in situations where dogs are housed together or gathered in groups, including:

• Boarding, grooming and daycare facilities  
• Animal shelters or pet stores where dogs are sold
• Dog shows, training groups, or competitions
• Dog parks
• Veterinary clinics

After being inhaled or ingested, the bacteria adhere to and damage the lining of the respiratory tract (trachea and bronchi), but in more advanced cases the lungs can also become involved. The incubation period (time from infection to onset of signs) is about six days (range of 2-10 days). Clinical signs may be worse with co-infections with viruses or other bacteria. 

What are the signs?

The most common feature is a loud, high-pitched, persistent “honking” cough. Dog owners may initially feel that their dog is trying to clear something from their throat. After an episode of coughing, the dog may cough up mucus. Coughing may be exacerbated by activity.

Other common signs may include:

• Sneezing and nasal discharge
• Ocular discharge
• Mild fever
• Lethargy
• Decreased appetite 

In more severe cases (especially with puppies) pneumonia can develop which may also be associated with labored breathing.

The severity of signs will vary from dog to dog, but most cases remain mild.

How is it diagnosed?

Diagnosis is primarily based on clinical signs and history of exposure to other dogs. In most cases, diagnostic testing is not required, especially if the dog is otherwise healthy and the symptoms are mild.

In more severe or persistent cases, your veterinarian may recommend:

• Complete blood count
• PCR testing to detect Bordetella bronchiseptica or other respiratory pathogens
• Bacterial cultures
• Chest X-rays to screen for pneumonia or other conditions

How is Bordetella treated?

Most dogs recover with supportive care and rest. In mild cases, treatment may not be necessary beyond monitoring. However, dogs with more intense symptoms may benefit from:

• Antibiotics effective for Bordetella bronchiseptica and secondary bacterial infections
• Cough suppressants, unless the dog has a productive cough or pneumonia  
• Glucocorticoids to reduce airway inflammation
• Other supportive treatments may include IV fluids, nebulization and oxygen

Vaccination for Bordetella

The Bordetella vaccine is considered a non-core vaccine, but it is highly recommended for dogs who are at risk. Many vaccinated dogs will not develop clinical signs following exposure to Bordetella, while others may have less severe clinical signs and shed at a reduced rate. 

There are multiple vaccine options that can be given orally, intranasally, or by subcutaneous injection. 

Vaccination should begin as early as 6–8 weeks of age, with boosters given annually, or more frequently in high-risk situations (every six months, as recommended by some veterinarians).

How long is a dog contagious?

Dogs with Bordetella can remain contagious, even after symptoms resolve, for up to eight weeks and potentially longer. During this time, they should avoid contact with other dogs to reduce the risk of spreading the infection.

The bacteria can survive in the environment for at least 10 days. Household bleach diluted one part to 32 parts water is an effective disinfectant.

Zoonotic potential

Bordetella bronchiseptica also causes disease in cats (as well as pigs, horses, rabbits and rodents) and, infrequently, has resulted in illness in people -- typically those with compromised immunity. At-risk dog owners may consider choosing the injectable vaccine over the intranasal or oral vaccines for their dog, as well as limiting their dog’s exposure to groups of dogs. It is also related to the two species of Bordetella that cause whooping cough in people. 

Outcome

Most dogs with Bordetella have mild disease and will recover fully within 7-10 days, especially if they are otherwise healthy and treated early. However, complications such as life-threatening pneumonia can arise in vulnerable dogs, resulting in a more guarded prognosis. Dogs can shed the bacteria for two or months, even after they have stopped showing clinical signs. 

Outcomes are improved through vaccination, reducing exposure for at-risk dogs and seeking prompt veterinary care.