Kennel cough is a tricky thing. Like human "colds and flu," it's a catch-all term that can refer to many highly contagious respiratory infections caused by different microbes, from viruses to bacteria to the peculiarly unclassifiable mycoplasmas. The vaccines in your pup's regular course of shots protect him against some of these pathogens, but leave him vulnerable to others.
The terms "kennel cough" and Bordatella are sometimes used interchangeably, but this isn't exactly correct. The more accurate term for kennel cough is "infectious tracheobronchitis." Bordatella is a genus of bacteria that includes one species, Bordatella bronchiseptica, that can cause respiratory infections in dogs. However, other pathogens, including canine adenovirus, parainfluenzas and influenzas, canine herpesvirus, mycoplasmas and Streptococcus bacteria can also cause infectious tracheobronchitis. Early stages of certain gastrointestinal infections and the extremely serious distemper and parvoviruses can also mimic kennel cough.
Shots in the Dark
If you've ever caught the flu right after getting a flu shot, you understand some of the difficulty with kennel cough immunization. Vaccines cover some of the microbes that cause infectious tracheobronchitis, but not others. Your pup's core vaccines include parvovirus, canine distemper and canine adenovirus -- also called canine hepatitis. If you opted to get him a Bordatella shot or nasal spray, he's protected against canine Bordatella bacteria as well. However, vaccines for the other kennel cough pathogens are either not available, or administered very rarely. Further complicating the issue, most vaccines aren't effective until several days after your pup gets the shot and they don't work if he's already infected, even if he wasn't showing symptoms when he was vaccinated.
Regardless of the responsible microbe, the most characteristic symptom of infectious tracheobronchitis is a loud, honking cough. A coughing dog usually stands with his head down and his front legs apart. Infected pups also discharge frothy white mucus from their noses and mouths and may have sneezing fits. Dogs with bacterial kennel cough infections may also produce copious quantities of green snot. All kennel cough infections are highly contagious and your puppy should stay away from other dogs.
When to Worry
Like human colds, kennel cough usually runs its course within three weeks. While your infected pup may appear tired and unhappy, it's also possible he'll be as active as normal, merely pausing to hack up a lung now and then. If your dog gets extremely lethargic and listless, it's been more than three days and his cough is getting worse rather than better, his phlegm is getting greener, he's vomiting or refusing food and water, get him to a vet. Some extremely serious infections start off looking like kennel cough, and some tracheobronchitis cases come down with life-threatening secondary infections, including pneumonia.