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Much like the “colds” we all catch, "kennel cough" is a catch-all term that includes a great number of different germs - all of which have the ability to make your dog cough and perhaps feel under the weather. Year after year, the number of infectious organisms veterinarians link to coughing dogs grows. And just like our common colds, the results of kennel cough can be no more than a passing annoyance lasting a day or two, or something serious enough to keep your pet indisposed for quite some time. And like colds, on rare occasion, the problem will morph into something considerably more serious (pneumonia) - almost always when other enabling health issues are present.
Veterinarians’ proper term for kennel cough is infectious tracheobronchitis. Many still associate the disease with a bacterium, Bordetella bronchiseptica. But bordetella rarely if ever causes kennel cough on its own. When bordetella is involved, it is generally only one of many players in a complex interaction between your dog’s immune system and an assortment of other viral and bacterial pathogens working in tandem. Those other players include the dog parainfluenza virus, an adenovirus, a coronavirus and a number of other players, all of whom I will tell you about as you read on.
Alone, few if any of these organisms produce more than a mild, transitory problem - if any at all. But together, under the right situations and in predisposed pets, they have a combined group power to make your dog ill. Many healthy dogs carry one or more of these organisms in their respiratory system. Wherever many healthy carrier dogs gather together, they exchange these organisms. That leads to new combinations of bacteria and virus that leave some of the dogs open to tracheal and bronchial inflammation (tracheobronchitis).
None of the organisms that are implicated in kennel cough persist in the environment. Dogs get infected by inhaling the coughs and sneezes of other dogs. So wherever lots of dogs are close together there is the potential to catch it. That can be a boarding kennel, a grooming salon, dog shows, doggy parks, animal shelters, traveling discount vaccination buses etc. Coughing and sneezing dogs generally shed the kennel cough-related organisms for 5-10 days. But dogs that are not sneezing or coughing shed these organisms too. (ref) Any dog within 6 feet of a sneezing dog is likely to inhale these organisms. (ref) But wind, drafts and ventilation systems can spread them much farther. It generally takes 3-5 days after exposure for your dog to become ill enough to cough. Once more than 10 days have passed, it is unlikely that anything more serious will occur. Remember that a lot of kenneled dogs bark continuously due to their unfamiliar confinement. Those dogs can leave hoarse and coughy too.
Objects in an environment shared with infected dogs can conceivably spread the disease to your dog as well – things like water bowls, toys and food dishes. But I do not believe that those are major way the disease moves from dog to dog.
Most pets experience only a dry, hacking or honking cough, sneezing and, perhaps, a subdued temperament. It is hard for veterinarians to notice minor mood changes in dogs because they are generally too alert or apprehensive during an office visit to exhibit them. Laryngitis can affect the tenor of their bark. Their tonsils may enlarge (bulge from their crypts) which sometimes affects their appetite and stimulates gagging and wrenching. If so, bubbly, mucus phlegm is all that is produced. Light pressure on their windpipe often brings on a period of coughing, as does a tight collar or taunt leash. The presence or absence of a low fever is unpredictable. So is the presence of eye and nasal exudate (discharge&crusts).
A few unfortunate pets develop secondary problems that produced considerably more exudate in their lungs (pneumonia). Those are generally pets under high stress or with pre-existing health issues, conformational issues, nutritional deprivation or a life under crowded unsanitary conditions.
Stress goes hand-in-hand with animal shelter life and boarding situations. Few dogs would choose being away from you, their owner and friend. How they handle such separation varies greatly from dog to dog. Elderly dogs with heart valve issues can already have too much fluid in their lungs - a recipe for pneumonia. (ref) I suggest you be particularly cautious in exposing them to kennel cough risk. Many popular toy breeds have a tendency to collapsed tracheas and narrow respiratory passages. Although they are no more susceptible to kennel cough than other breeds, the disease tends to linger on in them considerably longer. Other dogs face health issues that lower their ability to fight infections of all kinds. Still others, particularly those in shelters, arrive nutritionally deprived or with a heavy parasite burden. That also lowers their immunity to kennel cough. Advanced age in itself decreases the body’s ability to ward off and bounce back from many of the organisms involved in respiratory disease.
Several commercial laboratories and universities offer respiratory disease panels that search for and identify the DNA of organisms that are likely to invade the respiratory tract of dogs ( ref= ) Most of these tests do not attempt to grow or visualize the organisms. They rely on the PCR technique to amplify the distinct DNA/RNA of each of these organisms to provide enough material to identify the specific organism that is its source. The samples submitted from a dog are generally swabs taken from the pet’s throat (pharyngeal swabs) and/or nose.
However, these tests have their limitations. For one, perfectly normal looking dogs often carry some of these organisms as well. Samples submitted more than a few days after the infection begins can have too few organisms left to determine what initiated the coughing problem in the first place. The same "too few or none" problem occurs for bacterial player when antibiotics were initiated before the sample was obtained. Where these tests are helpful is in developing a treatment plan for an animal shelter or large scale animal care facility where samples from many ill and healthy dogs, submitted at the same time, might give them clues as to how to best approach and reduce a continuing problem.
As I mentioned earlier, significant cases of kennel cough in healthy dogs are rarely due to one organism alone. It is no different in humans, where over 200 organisms alone have been implicated in tracheobronchitis (colds). The fact that many of these organisms are only fleetingly present in the body means that just finding bordetella does not mean that it acted alone. There are considerably more healthy dogs carrying bordetella than coughing dogs. (rptref1, ref2)
Bordetella b. is not that particular which species it inhabits. Besides dogs; cats, ferrets, guinea pigs and rabbits carry the organism and occasionally suffer its ill effects (ref) On rarer occasion, elderly and immunosuppressed humans are susceptible to its pathology as well. (ref) The location of choice for Bordetella is adjacent to the cilia that line your dog’s larger lung passages (the trachea & bronchi) (ref) These cilia are the "brooms" that are constantly sweeping inhaled debris, dust, mucus and bacteria forward and out of your dog's lungs. The plentiful mucus that the dog’s respirator system naturally secretes traps invading organisms and that, along with its immune system, normally limit the organism's ability to do damage. Under conditions of stress, the bordetella bacteria could, perhaps, act alone to cause kennel cough. But with the list of secondary players increasing year by year, that has not been adequately established. On occasion, bordetella is isolated from severe pneumonia in dogs or from the lungs of puppies that have inhaled milk (aspiration pneumonia). The importance of its role in those situations also remains unclear. (ref1, ref2)
Mycoplasma (sometimes called mollicutes) are an extremely small variety of bacteria. Many different species of mycoplasma have been isolated from dogs – some of which showed respiratory tract issues and some dogs that did not. When mycoplasma are searched for, suspicion often falls on Mycoplasma cynos because it is a common resident in coughing dogs. (ref) But as with bordetella, healthy dogs often carry it too. (ref1, ref2)
Although some antibiotics inhibit mycoplasma, they are quite difficult to totally eliminate (kill). (ref)
Other bacteria, such as Streptococcus zooepidemicus, Pseudomonas, E. coli, and Klebsiella have also been isolated from the respiratory tract of dogs with infectious coughs.
Another bacterial group, the Chlamydophila, are occasionally isolated from coughing dogs as well. (ref) Chlamydophila and chlamydia are not currently the same thing - although there are still quite a few microbiologists like me grumbling about that.
A virus that is often isolated from dogs with kennel cough is the canine adenovirus-2 (CAV-2). Many dogs will develop a cough within a week of being exposed to this virus. In some dogs, the CAV-2 virus also causes conjunctivitis, sneezing and a nasal discharge. When your dog is exposed to just this virus, the signs are generally quite mild. But as with the rest, when the dog is exposed to it along with other villains, the cough and malaise can be more serious. The shots your dog received against distemper and parvo, generally also contained weakened (attenuated) CAV-2 virus. That is because they give cross-protection against CAV-1, the virus that causes canine infectious hepatitis. (ref)
Like the canine Adenovirus-2, weakened parainfluenza virus (CPIV) is included in most of the shot formulas that include distemper and parvo. It is also included in the intranasal “kennel cough” vaccines such as Bronchi-Shield® III and Vangard® RR-3 As with the other virus and bacteria associated with kennel cough, the signs of this virus are indistinguishable from the others. (ref) None of the parainfluenza virus-containing vaccines claim to prevent infection with this virus (to confer “sterile” immunity) what they do claim is that they tend to make infections with the virus less severe when they occur. (ref)
Like the adenovirus, this virus also comes in two forms: A contagious intestinal disease that can be found in dogs all around the world (CCV group 1) and a respiratory tract form (CRCoV) group 2 that is usually mild. It is unclear if these two viruses have the ability to cross-infect targets or merge - with possible severe effects if they do (target organ pantropism). (ref)
Between 2008 and 2009, Veterinarians in the UK and at Cornell University isolated yet another virus from coughing dogs housed at animal shelters. It proved to be a pneumovirus. (ref) Where - if anywhere - it fits into the kennel cough complex remains to be determined.
Canine influenza is usually considered a separate, and potentially more serious disease than kennel cough. But the symptoms overlap. When they are mild, the symptoms of CIV are indistinguishable from kennel cough (although CIV is more associated with fever than the disease agents I mentioned previously).
Florida is a central hub for greyhound racing. The housing of greyhounds has the same disadvantages of animal shelters – crowded conditions, limitations on individual care, high stress and the mixing of animals from different locations in close proximity. The flu virus first appeared in Florida greyhounds in 2004. Flu viruses have the ability to jump species and mutate rapidly. This particular variant was labeled H3N8. For over 40 years, it had only been know to circulate among horses. Since then, another flu variant, H3N2 (associated with chickens [ref] )has also been isolated from coughing dogs. Neither have ever been reported to cross over to people - yet. By 2016, canine influenza had already jumped to cats. On November 6, 2018, the Sunshine State banned greyhound racing - hopefully due to the cruelty of the sport and not canine influenza.
When CIV gets into a group of dogs, 60-80% are likely to begin to show signs in 2-5 days. The virus is usually out of their system 7 days later. When signs last longer, they are usually due to the organisms associated with kennel cough being involved as well. Vaccines against CIV minimize the risk of your dog developing respiratory tract signs like sneezing, coughing and malaise, but they do not altogether prevent infection. The lifestyle risk factors for CIV are the same as those for kennel cough.
Like canine influenza, the dog distemper virus is not a part of kennel cough. But like influenza in dogs, the early signs of distemper often include a cough and other signs that might be mistaken for kennel cough. The weakened immune system that distemper induces also gives the organisms involved in kennel cough and other health issues an increased opportunity to prosper. (ref)
We usually think of the herpes virus of dogs as a cause of sudden death in puppies. (ref) Once an adult dog is exposed to that virus and recovers, just like in human cases of herpes and chickenpox, the virus tends to persist (latently) in the body for life. However, in dogs that are not newborn, nor mature, herpes virus of dogs has the ability to cause symptoms that mimic those of kennel cough. (ref) It might even be capable of doing so in mature carrier dogs when they are subjected to stress that suppresses their immune system or drugs (eg corticosteroids, cyclosporin) that have that effect as well.
Murine reoviruses (MRVs), like the bordetella bacteria, are also not that particular in which species they choose to reside. They have been isolated from the respiratory tracts of dogs with kennel cough. What part, if any, they play in the disease has yet to be determined.
Once your veterinarian has eliminated non-infectious causes for your dog’s cough, antibiotics are probably something you will leave with.
No surveys I know off list the preferred antibiotics used for kennel cough in the United States. But in Australia, known for its high caliber of veterinary care, doxycycline, amoxicillin/clavulanate (Clavamox®), enrofloxacin (Batryl®), amoxicillin and cephalexin lead the list. (ref) That is not to say that mild cases will not recover without them or that the antibiotics will be of any aid in treating the viral organisms that are most often also involved. In the USA, add chloramphenicol to the list and downgrade Clavamox and ampicillin for the ability of bordetella to resist them. In the USA - other than when it is absolutely necessary - Batryl® is frowned upon in immature dogs because of its possible negative effects on joints that are still developing. In severe cases, some veterinarians have nebulized gentamycin to kennel cough dogs.
The Koret Shelter Medicine Program at Davis discourages the use of prescription cough suppressant (antitussive) medications (like Temaril-P® and Hycodan®) The former contains a steroid that can suppress immune function. The second, a narcotic, can decrease the ability of the respiratory system to clear itself of mucus and debris. Over the counter cough suppressants are not particularly effective. Nor are bronchodilators.
If your dog is running a fever, your veterinarian might prescribe a dog-safe NSAID.
Your veterinarian will probably tell you to give your dog a comfortable warm environment with plenty of rest. The vet might suggest you not do anything that encourages your dog to bark. He/she might tell you to be sure its collar is not to tight and suggest you use a harness rather than a leash until the cough resolves. If poor appetite is a problem, consider a canned or home-cooked diet rather than a dry one.
A call back to your veterinarian is prudent if the problem persists or gets worse. Let them know if the consistency, amount or color of it nasal discharge changes or if its respiratory rate or effort increases. Listlessness is never a good sign.
The vast majority of kennel cough cases resolve without complications. But veterinarians never want the problem to progress to pneumonia - so they will want to keep track of your dog as it recovers.
There are three forms of kennel cough vaccines on the market: intranasal, oral and injectable.
Bronchi-Shield® and Vanguard® B Oral formulas only contain bordetella – offering no protection against the other common causes of kennel cough. The injectable products I am familiar with only offer protection against bordetella as well.
My preference is for the products that are administered in your dog’s nose because the intranasal vaccines against kennel cough that I use protect against bordetella, canine adenovirus-2 and parainfluenza. I believe that they are also more likely to stimulate immunity where it is needed – in your dog’s nose and upper respiratory system. (ref) One study I know of found that that was also the case in dogs. (ref)
The best prevention is to expose your dog to other non-family dogs as little as possible. Wandering cats can also carry many of these organisms – so keep your cats indoors.
All the situations that would make it more likely for you to catch a cold are the same situations that make it more likely for your dog to catch kennel cough – the only way the virus travels to your dog is through another dog and anything that lowers your pet’s resistance increases its susceptibility.
One study, quoted by the U. Wisconsin Veterinary School, showed that each day in a shelter increased the risk of kennel cough by 3%
Some believe that intranasal kennel cough vaccines give immediate protection through their stimulation of local immunity. But shots and oral vaccines given less than 7-10 days before your dog enters a boarding kennel or other high-density-dog environment offer your pet little if any immediate protection
I suppose that if some of the oral vaccine makes its way into your dog’s respiratory tract rather than its stomach, it might be of some immediate value as well.