An uncomplicated kennel cough runs a week or two and entails frequent fits of coughing in a patient who otherwise feels active and normal. Uncomplicated cases do not involve fever or listlessness, just lots of coughing.

Numerous organisms (some of which may be prevented by vaccination) may be involved in a case of kennel cough; it would be unusual for only one agent to be involved.

Infections with the following organisms frequently occur concurrently to create a case of kennel cough:

1. Bordetella bronchiseptica (bacteria)
2. Parainfluenza virus
3. Adenovirus type 2
4. Canine distemper virus
5. Canine influenza virus
6. Canine herpesvirus (very young puppies)
7. Mycoplasma canis (a single-cell organism that is neither virus nor bacterium)
8. Canine reovirus
9. Canine respiratory coronavirus.

The classical combination for uncomplicated kennel cough is infection with parainfluenza or adenovirus type 2 in combination with Bordetella bronchiseptica. 

Infections involving the distemper virus, Mycoplasma species, or canine influenza are more likely to progress to pneumonia, and pneumonia can readily result in any dog or puppy that is sufficiently young, stressed, or debilitated.

Not sure what a Coughing Dog sounds like?

Dogs can make assorted respiratory sounds. Usually, a cough is recognizable but it is important to be aware of another sound called a reverse sneeze. The reverse sneeze is often mistaken for a cough, a choking fit, sneezing, retching, or even for some sort of respiratory distress. The reverse sneeze is a post-nasal drip or tickle in the throat. It is considered normal, especially for small dogs, and only requires attention if it is felt to be “excessive”. The point here is to know a cough when you hear one. A cough can be dry or productive, meaning it is followed by a gag, swallowing motion, and the production of foamy mucus (not to be confused with vomiting). Here are some videos that might help.

Coughing Dog (with Productive Cough): Dixon has kennel cough

Note: We have received a great deal of emails from people who have viewed this video, compared it to what their own dog is doing, and concluded their dog has kennel cough. This video is meant to demonstrate coughing in general. It is important to note that there are many causes of coughing and the nature of the cough does not generally reflect on its cause.

Reverse Sneezing Dog: Maggie reverse sneezes

How Infection Occurs

An infected dog sheds infectious bacteria and/or viruses in respiratory secretions. These secretions become aerosolized and float in the air where they can be inhaled by a healthy dog. Obviously, crowded housing and suboptimal ventilation play important roles in the likelihood of transmission but organisms may also be transmitted on toys, food bowls, or other objects.

The cilia beat in a coordinated fashion through the lower and more watery mucus layer called the sol. A thicker mucus layer called the gel floats on top of the sol. Debris, including infectious agents, gets trapped in the sticky gel and the cilia move them upward toward the throat where the collection of debris and mucus may be coughed up and/or swallowed.

The mucociliary escalator is damaged by the following:

1. shipping stress
2. crowding stress
3. heavy dust exposure
4. cigarette smoke exposure
5. infectious agents (as listed previously)
6. cold temperature
7. poor ventilation.

Without this, a fully functional mucociliary escalator or invading bacteria, especially Bordetella bronchiseptica, the chief agent of kennel cough, may simply march down the airways unimpeded.

Bordetella bronchiseptica organisms have some tricks of their own as well:

• They can bind directly to cilia, rendering them unable to function within 3 hours of first contact.
• They secrete substances that disable the immune cells normally responsible for consuming and destroying bacteria.

Because it is common for Bordetella to be accompanied by at least one other infectious agent (such as one of the viruses listed below), kennel cough is a complex of infections rather than infection by one agent.

Classically, dogs get infected when they are kept in a crowded situation with poor air circulation and lots of warm air (i.e., a boarding kennel, vaccination clinic, obedience class, local park, animal shelter, animal hospital waiting room, or grooming parlor). In reality, most causes of coughing that begin acutely in dogs are due to infectious causes and usually represent some form of kennel cough.

The incubation period is 2 to 14 days. Dogs are typically sick for 1 to 2 weeks. Infected dogs shed Bordetella organisms for 1 to 3 months following infection.

How is a Diagnosis Made?

A coughing dog that has a poor appetite, fever, and/or listlessness should be evaluated for pneumonia.

Usually, the history of exposure to a crowd of dogs within the proper time frame, plus typical examination findings (coughing dog that otherwise feels well) is adequate to make the diagnosis. Radiographs show bronchitis and are particularly helpful in determining if there is a complicated pneumonia.

Recently, PCR (polymerase chain reaction) panels have become available in many reference laboratories. Using technology to amplify the presence of DNA in a swab, the lab is able to test for most of the kennel cough infectious agents listed. This knowledge is helpful in guiding therapy and understanding expectations.

How is Kennel Cough Treated?

An uncomplicated case of kennel cough will go away by itself. Cough suppressants can improve patient comfort while the infection is resolving. The dog should be clearly improved, if not recovered, after about a week. That said, several infectious agents in the kennel cough complex are more intense and can cause minor bronchitis to progress to pneumonia, which is a potentially life-threatening disease. Given this possibility, antibiotics are frequently prescribed to kennel cough patients to prevent or curtail pneumonia before it warrants hospitalization.

It is important to distinguish an uncomplicated case of kennel cough from one complicated by pneumonia for obvious reasons. The uncomplicated cases will not have a fever or appetite loss, nor will they be listless. As mentioned, they will seem normal except for coughing. Dogs with pneumonia appear sick.

Prevention through Vaccination

For Bordetella bronchiseptica, vaccination can either be given as a separate injection or as a nasal immunization. There is some controversy regarding which method provides a better immunization or if a combination of both formats is best.

Nasal Vaccine

Intranasal vaccination may be given as early as 3 weeks of age and immunity generally lasts 12 to 13 months. The advantage is that local immunity is stimulated right at the site where the natural infection would try to take hold.

It takes four days to generate a solid immune response after intranasal vaccination, so it is best if vaccination is given at least four days prior to the exposure. Some dogs will have some sneezing or nasal discharge in the week following intranasal vaccination; this should clear up on its own. As a general rule, nasal vaccination provides faster immunity than injectable vaccination.

Nasal vaccines for Bordetella generally also include a vaccine against parainfluenza virus and some also include a vaccine against adenovirus type 2.

Oral Vaccine

An oral vaccine is available for Bordetella bronchiseptica (but not adenovirus or parainfluenza). The idea is that it is easier to give the vaccine with a syringe in the mouth – just inside the cheek – and there is no concern about sneezing out some of the vaccine. The oral vaccine can be given to puppies as young as 8 weeks of age. The vaccine is given annually.

Injectable Vaccine

Injectable vaccination is a good choice for aggressive dogs who may bite if their muzzle is approached. For puppies, injectable vaccination provides good systemic immunity as long as two doses are given (approximately one month apart) after age 4 months. Boosters are generally given annually. Some dogs experience a small lump under the skin at the injection site. This should resolve without treatment.

Vaccination is not useful in a dog already incubating kennel cough.

Bordetella bronchiseptica vaccination may not prevent infection. In some cases, vaccination minimizes symptoms of illness but does not entirely prevent infection. This is true whether nasal, oral or injectable vaccine is used.

Dogs that have recovered from Bordetella bronchiseptica are typically immune to reinfection for 6 to 12 months.

What if Kennel Cough doesn’t Improve?

As previously noted, this infection is generally self-limiting. It should be at least improved partially after one week of treatment. If no improvement is seen after that week, a re-check exam (possibly including chest radiographs) would be a good idea. Failure of kennel cough to resolve suggests an underlying condition. Kennel cough can activate a previously asymptomatic collapsing trachea or the condition may have progressed to pneumonia. Alternatively, there may be another disease afoot entirely such as non-infectious bronchitis, congestive heart failure, or some other condition that causes coughing.

If you have questions about a coughing dog, do not hesitate to bring them to your veterinarian.

What is Congestive Heart Failure?

• If the right side of the heart is diseased, fluid is retained mostly in the belly or within the pleural cavity.

Why Does CHF Occur?

CHF occurs because the pressure in the veins and capillaries draining into the diseased side of the heart increases to the point that fluid leaks out of the veins and capillaries. The capillaries and veins that drain into the left side of the heart are those coming from the lungs, so fluid leaks into the lungs. The capillaries and veins that drain into the right side of the heart are those coming from the body, so fluid leaks into the belly (ascites) or creates swelling in the legs, the skin under the belly, etc.; swelling of the legs or the skin is uncommon in dogs and cats with right-sided CHF, but much more common in humans and horses.

It can be useful to think of this like a garden soaker hose. If water is flowing through the hose under low pressure, only a little bit of water leaks through the soaker hose. However, if we increase the pressure inside the hose, water starts to emerge from the soaker hose at a much greater rate and floods your garden. The same happens with the capillaries – under low pressure, only a little fluid leaks out of them (and is resorbed). But if the pressure is too high, a large volume of fluid leaks out into the surrounding tissue, and overwhelms the resorption mechanisms.

What Causes CHF?

CHF requires severe heart disease that increases the resting (diastolic) cardiac pressure. For example, diseases that cause leakage of valves (mitral or tricuspid valve disease) can result in CHF if the leak is big enough. Cardiomyopathies also cause the resting cardiac pressure to increase and can result in CHF. Pericardial diseases can prevent the heart from relaxing and stretching properly, which can result in right-sided CHF. Heartworm disease can cause right-sided CHF. Many congenital defects that shunt blood can result in CHF (e.g. patent ductus arteriosus, ventricular or atrial septal defects).

Importantly, congenital diseases that obstruct outflow from the heart, such as pulmonic stenosis or aortic stenosis, do not normally cause CHF.

What Are the Clinical Signs of CHF?

This depends on the side of the heart that is diseased. Let’s start with left-sided CHF, which causes pulmonary edema and, sometimes, pleural effusion. As fluid starts to deposit fluid into animals’ lungs, the amount of oxygen in the blood decreases because it can’t be absorbed from the lungs. Human patients describe this as shortness of breath, initially during exertion, such as climbing stairs, and eventually even when stationary. However, animals cannot tell us if they are short of breath. Sometimes, owners will notice a decrease in exercise ability, such as not going as far on walks and getting winded on walks more quickly. However, many things can cause exercise intolerance. Therefore, we tend to look for an increase in breathing (respiratory) rate, especially when sleeping.

Coughing has been described as a feature of CHF in dogs, but there is some doubt as to whether CHF really causes coughing or not. Again, many dogs and cats cough for reasons other than heart disease. As the fluid continues to build up, dogs and cats will also show difficulty in breathing as well as a faster respiratory rate. This is especially true of cats, who can hide their disease until it becomes really advanced. Consequently, many cats see veterinarians with labored, open-mouth breathing that is almost gulping for air, which appears to have started all of a sudden. In dogs, the clinical signs can be more gradual and subtle.

With right-sided CHF, the most common presentation is a swelling of the abdomen (ascites), making the dog appear pregnant. The discomfort from a belly full of fluid results in difficulty getting comfortable or breathing comfortably when lying down. These dogs will even resort to sleeping in a sitting position at times! Appetite often decreases slightly because of the abdominal pressure.
If there is a buildup of fluid in the chest cavity, the animal might show difficulty in breathing.

How Do Veterinarians Diagnose CHF?

The diagnosis of CHF relies on pairing the clinical signs of increased respiratory rate and difficulty in breathing with the severe heart disease that is responsible for these clinical signs. Many times, a murmur can be heard for the first time. The pet’s heart rate will be elevated, their respiratory rate will be elevated. Some cats come in with a low body temperature because they are somewhat shocky from inadequate oxygen.

If veterinarians suspect CHF, they will generally take chest X-rays to see if there is evidence of (A) severe heart disease that appears as an enlarged heart; and (B) opacity (areas through which light does not pass) in the lungs consistent with pulmonary edema, or fluid in the chest cavity consistent with pleural effusion. If they are unsure or require additional information, they might perform or recommend a cardiac ultrasound. Those are often performed by specialists, typically veterinary cardiologists or radiologists, who have the necessary equipment.

How Do we Treat CHF?

Treatment is directed at both the underlying heart disease and the accumulation of fluid. If possible, the cause should be corrected. For example, closing a congenital shunt, such as a patent ductus arteriosus, will immediately correct the problem permanently. Repairing a leaking mitral valve will also correct the problem almost immediately, although this procedure is currently very expensive and performed by a limited number of surgeons.

The mainstay of medical treatment of left-sided CHF is the use of diuretics called loop diuretics, which include furosemide or torsemide. Diuretics reduce blood volume and consequently reduce the pressure in the veins, forcing the fluid out into the lungs or the abdomen.

Other drugs that are commonly used to treat CHF include angiotensin-converting enzyme inhibitors, pimobendan, thiazide diuretics, and spironolactone. These are much less effective than loop diuretics and should never be given as the only drugs for managing CHF. Indeed, if a dog or cat does not require a diuretic, they most likely do not have CHF.

The fluid buildup in right-sided CHF often requires repeated manual removal, using large catheters to make the patient feel better. In many dogs, this can be done as frequently as every week or two. Ideally, when coupled with medical treatment, the frequency of belly taps can be reduced somewhat.

How Do we Monitor CHF?

The most important thing to monitor with left-sided CHF is respiratory rate. Provided the respiratory rate when sleeping is in the normal range, we can be reasonably confident that we have good control of the CHF. When the sleeping respiratory rate starts to increase, adjustments in treatment might be necessary; a veterinarian will evaluate the patient to determine exactly what to do in such instances. (See monitoring videos below.)

Many veterinarians will monitor bloodwork to make sure that the medications being given are not causing problems with kidneys or elsewhere.

If a pet appears to destabilize after a period of control, additional x-rays might help better evaluate the situation.

What is the Prognosis?

This depends somewhat on the underlying disease. With the more common diseases, such as mitral valve disease in dogs or hypertrophic cardiomyopathy in cats, once CHF is diagnosed and treatment instituted, survival is generally less than two years. With mitral valve disease, approximately 50 percent of dogs will succumb to their disease within 8 to 10 months, and only 20 percent live for 18 to 24 months. With hypertrophic cardiomyopathy survival data are less clear, but some older studies suggest that 50 percent of cats will succumb to the disease within 7 to 10 months. As is always the case, a few individuals will live longer than expected.