Kennel Cough: Causes, Signs, Diagnosis, Treatment

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Kennel cough is the older name given to upper respiratory tract infections in dogs. It was classically associated with dogs going to kennels and was associated with either a Bordetella bronchiseptica or canine parainfluenza (CPIV) infection. These are the components of what most people consider the “kennel cough” vaccine. However, there are many other infectious causes of a dry, hacking cough. In fact, in different geographic locations, some of the other infectious causes are a lot more common than bordetella or parainfluenza.

Furthermore, dogs do not get this cough just at boarding kennels. Dogs can pick up an infectious cough just about anywhere they come into contact with other dogs — in animal shelters (especially ones with poor ventilation) and veterinary hospitals and at dog shows, dog parks and the groomer’s. The more accepted name in the veterinary community is now canine infectious respiratory disease (CIRD).

Dog health: signs of a healthy dog

Causes of upper respiratory tract infections in dogs

In addition to bordetella and parainfluenza, causes of an infectious cough in dogs include canine distemper (CDV), canine adenovirus type 2 (CAV-2), canine influenza (CIV), canine pneumovirus (CnPnV), canine respiratory coronavirus (CRCoV), canine herpesvirus (CHV), pantropic canine coronavirus, canine reovirus, mycoplasma, and Streptococcus equi subspecies zooepidemicus. The last two, along with bordetella, are bacteria. The others are viruses.

Any dog exposed to one of these pathogens can be infected. However, a dog is much more likely to be infected in a moist, warm environment with poor ventilation and with repeated exposure, such as in a kennel or a shelter. It is very common for shelters to have to quarantine a whole section once an infectious cough breaks out because it spreads so easily and quickly. Yet, even a simple exposure that occurs during a quick meeting at a dog park is enough to transmit the infection.

Mild and severe symptoms of kennel cough

Once a dog is exposed, it usually takes two or three days before he starts to show signs, but it can be up to 10 days. The one exception to this is canine distemper. With distemper, it can take up to four weeks before signs are noted. The most common signs are typically mild and include a cough (especially when pressure is applied to the trachea or windpipe), sneezing and eye discharge. The cough can often sound like the dog is retching or it could be described as dry and hacking.

In more severe infections, the dog can have a fever and may have trouble breathing. He will not be interested in eating and will appear to be very tired. The more severe signs tend to occur in unvaccinated dogs, dogs with weak immune systems, such as puppies or dogs with other illnesses, and with some of the different pathogens, such as canine influenza virus, canine distemper virus and streptococcus. However, any of the infectious agents can lead to serious signs. It is impossible to know which agent is causing the cough based on clinical signs alone.

Canine infectious respiratory disease diagnosis

Most veterinarians can diagnose CIRD based on clinical signs alone. However, they may take chest radiographs (which is the technical name for X-rays) to make sure that pneumonia is not present, as this circumstance would change the treatment.

It is possible to figure out what the underlying cause is, but it’s often not necessary (or worth the expense) for an individual animal unless he does not respond to initial therapy, if there are signs of more aggressive disease, if multiple dogs are coming down with the same signs at the same time, or if there is an outbreak in a shelter or kennel. In the case of a shelter or kennel outbreak, it is important to know the underlying cause because it will dictate what cleaning agents are necessary, how long quarantine should be, and if vaccine recommendations should be changed for that organization.

To figure out what the causative agent is, a culture can be taken of the upper airway. However, this typically requires sedation and only covers bacteria; it will not diagnose viruses. In the last five years, it has been more customary to do a swab of the nose and deep throat, and send out for polymerase chain reaction (PCR) tests to look for genetic material of the causative agent. These tests can test for everything, do not require sedation, and are relatively affordable compared to doing other tests for each individual organism.

Kennel cough treatment

The traditional treatment for a dog with a cough is starting antibiotics. Ideally, the antibiotic chosen is based on culture results, but often an antibiotic such as doxycycline is chosen, as it takes care of the more common bacterial causes of CIRD. There is controversy about when and if to start antibiotics, since most of the causes of CIRD are viruses, and therefore antibiotics do not directly treat them. However, it is not uncommon for secondary bacterial infections to occur, especially in sensitive dogs such as puppies or dogs with weak immune systems. Antibiotics may prevent progression to more serious disease. In many situations, though, cases of CIRD are self-limiting (similar to the common cold in humans) and the symptoms will resolve on their own without treatment.

Most veterinarians will start antibiotics if the dog has a fever, if he is very lethargic, if there is yellow or green discharge, if the dog is not eating or if the cough is getting worse instead of better after a few days. Antibiotics are also started if a culture dictates that treatment or if the PCR test reveals a more aggressive bacterial infection, such as streptococcus. Streptococcus has a greater likelihood of making a dog very sick and can even result in death. Antibiotics can also shorten the shedding period (the time a dog is contagious to other dogs), so they are often considered in cases in the shelter environment, in order to control the spread to the rest of the population.

If the cough is severe enough, a cough suppressant may be prescribed. These medications can make an animal more comfortable, but they can make it harder for him to clear the infection. Coughing is a way to expel mucous and infectious agents, so decreasing the cough can be counter-productive.

There is no easy home remedy to cure kennel cough other than time. Most dogs will clear the infection themselves in 10-14 days (with the exception of distemper, which can take weeks or months to clear). As long as the dog is acting fine otherwise and the cough is not worsening, you could wait before doing any treatment. We still recommend taking the dog to a veterinarian, however, to make sure no other interventions are needed first. It can be helpful to nebulize the dog with some sterile saline. A nebulizer can be used for about 10 minutes twice a day to help keep the dog’s airway moist.

In addition to clearing the signs of infection, most dogs are not contagious after 10-14 days of being ill, especially if antibiotics are used in bacterial infections. The exception to this, of course, is the canine distemper virus, which can be shed for weeks or months. So, it is important to keep a coughing dog away from other dogs for 10-14 days.

Prognosis for dogs with CIRD

For most cases of CIRD, the prognosis is very good. Most dogs do not even require treatment and recover on their own within 10 days. If pneumonia is present, much more aggressive therapy is required, but dogs typically recover if this therapy is administered.

A poorer prognosis occurs with dogs who have concurrent respiratory disease, such as a collapsing trachea or upper airway constrictions. Brachycephalic breeds (short-nosed dogs such as pugs, bulldogs and Boston terriers) with CIRD need to be treated more aggressively because their compromised airway makes them more prone to getting secondary bacterial infections, and they have a harder time clearing the infection.

As stated earlier, dogs with weak immune systems also have a more guarded prognosis. Puppies, dogs with immune-mediated disease, dogs on immunosuppressive drugs such as prednisone, and dogs with cancer are all more likely to require more intensive therapy and have a poorer prognosis.

Even though the signs are very similar regardless of the infectious agent involved, which infectious agent can have a significant impact on prognosis. For instance, untreated dogs with Streptococcus equi subspecies zooepidemicus can die.

Dogs vaccinated for the CIRD pathogens have a much better prognosis. Vaccination does not completely prevent infection in most cases, but it can dramatically reduce the duration and severity of disease.

Prevention of kennel cough with canine vaccinations

The easiest form of prevention is vaccination. Vaccines are available for canine distemper, canine parainfluenza virus, canine adenovirus type 2, canine influenza virus and bordetella. Of these, the distemper, parainfluenza and adenovirus vaccines are part of the core vaccines that most veterinarians administer. The bordetella vaccination is typically reserved for dogs at significant risk, such as those who frequent kennels, doggie daycare and the groomer’s. Currently, the canine influenza vaccine is typically done only in areas where there have been significant outbreaks or for dogs who travel a lot and might go to an outbreak area.

It is important to remember that the vaccines do not prevent infection or prevent a dog from spreading one of the pathogens. However, vaccines do decrease the duration and severity of illness. The one exception is the canine distemper vaccine, which does actually help prevent a dog from being infected. Because of this, along with the negative characteristics of canine distemper (taking longer to show signs, being shed for a longer period, the possibility of long-term problems and even death), many veterinarians recommend that dogs be vaccinated for distemper at an early age and be given boosters throughout their lives.

The fact that most vaccines do not prevent infection is part of the answer to the question of why a dog might still get kennel cough (again, more correctly, CIRD) even though he has been vaccinated with the kennel cough vaccine (which is normally a combination of bordetella and parainfluenza virus). Another part of the answer to that question is the fact that of the 11 common pathogens that cause CIRD, there are vaccines for only five of them. When outbreaks of coughing happen at a kennel, the culprit is usually one of the five that cannot be vaccinated for.

Vaccinations also do not take effect immediately, since it takes time for the dog’s immune system to respond to the vaccine and develop protection. Depending on the pathogen and the vaccine type, this process can take two weeks or longer.

It is also important to remember that puppies aren’t considered fully vaccinated until they are at least 4-5 months old. When puppies are born, they acquire some protection from infectious disease from their mother, through maternal antibodies. Over time, maternal antibodies decrease, though the rate is different for each individual (and can even be different for individual puppies in the same litter). Maternal antibodies, however, can interfere with vaccination protection, causing vaccines to be ineffective, even when the protection left from mom isn’t enough to protect the puppy from disease. After about three months of age, maternal antibodies are low enough not to interfere, so a puppy needs at least two vaccines after maternal antibodies have disappeared to be protected.

The other part of prevention is avoidance. Especially when there are outbreaks of a cough in an area, you should avoid bringing your dog to places where dogs congregate. In some circumstances, of course, it is not possible to avoid a kennel, the veterinarian’s office or even the groomer’s. When this is the case, it is important to limit the length of a stay and find a kennel with good ventilation and outdoor access. For animals who are prone to more serious illness from CIRD, finding a pet sitter or at-home groomer is the best situation. Again, those more prone to serious illness include puppies, dogs with other diseases (especially respiratory diseases) and short-nosed dogs.

How often to vaccinate a dog

Additional information on canine distemper

As noted previously, the canine distemper virus is one of the possible viral causes of CIRD. There are some very important differences, however, between distemper and the other respiratory pathogens.

Clinical signs of distemper (e.g., a dry, hacking cough) can be identical to those of other causes of CIRD. In about 10% of cases, though, neurological signs (seizures, tremors) can occur. In some cases when neurological signs are present, the dog will recover completely; in other cases, the neurological signs remain for life. In rare cases, a dog will appear to recover from respiratory disease and then will develop neurological signs weeks later.

Distemper more frequently causes pneumonia than the other causes of CIRD. In addition, distemper infects more than just the respiratory system, so a variety of other signs can occur (neurological, as discussed above, but also urinary symptoms and gastrointestinal signs like vomiting and diarrhea). In young puppies, distemper is frequently associated with a high fatality rate. Most adult dogs, particularly those with partial immunity from a recent vaccination, will survive.

Unlike most CIRD pathogens, distemper has a longer incubation period — the period between when a dog is exposed to a disease and when he starts to show symptoms. The typical incubation for distemper is 10-14 days, though it can be as long as a month.

Distemper can also be shed for long periods of time, which means a dog who is no longer showing any symptoms may still be contagious to other unprotected dogs. Shedding typically lasts for about a month, but it can last for several months in some cases. Contagiousness can be monitored by repeating respiratory PCR testing; consecutive negative tests can confirm that a dog is no longer contagious.

Treatment for distemper is symptomatic, as it is a virus. Antibiotics are often administered to protect against or to treat pneumonia. Anti-convulsants and muscle relaxants may control some of the neurological signs. If gastrointestinal signs are present, medications to help with nausea and diarrhea can be administered. And fluids are often given to the dog to maintain hydration during periods of decreased appetite and vomiting or diarrhea.

While distemper is a more serious cause of CIRD, even dogs with distemper can survive, depending on the dog’s previous vaccinations, age and concurrent illnesses. Distemper is more widespread than many people realize (it’s common in many regions of the southern U.S.), but it is important to keep in mind that it’s not the death sentence we once thought. Though distemper can be very serious or fatal in some cases, many dogs do well and go on to live completely normal, happy lives.