Asthma in Dogs or Bronchitis?
by Dr. Audrey Harvey, BVSc (Hons)
Dog owners are usually quite concerned when their dog develops a long-standing cough or wheeze, and rightly so. They worry that their four legged family member is suffering from asthma. However, veterinary specialists agree that dogs don't get asthma as we understand it, but instead they develop bronchitis.
The difference is that asthma is a condition characterized by sudden narrowing of the airways, after a person (or cat) has been exposed to something they are allergic to. In contrast, bronchitis is an inflammation of the airways, resulting in excess mucus and a chronic cough.
Causes of wheezing and chronic coughing in dogs
There are many causes of these symptoms in dogs, with some being easier to diagnose and treat than others.
• Some breeds are predisposed to upper airway problems that lead to wheezing and coughing. Norwich terriers are such a breed. Other small dogs such as Chihuahuas and Pomeranians can have collapsing tracheas, and they show similar symptoms.
• Obese dogs can have difficulty breathing just because they are so fat. If they lose weight, their breathing often becomes easier.
• If a dog has a lung disease such as pneumonia, they can be left with residual airway disease. They may cough and wheeze long after the original problem has cleared up.
• Although allergies rarely cause breathing problems in dogs, it's worth keeping them in mind as one of the less likely culprits. Allergic bronchitis may only occur at certain times of the year, when a particular plant is flowering, or it may be a year round problem.
• A dog can get a foreign body in its throat or airways that will cause a partial obstruction. The wheeze occurs when the air passes by it, and the dog will cough to try and dislodge it.
The symptoms of chronic bronchitis in dogs can be varied, and they can also range in severity from just a mild noise to difficulty breathing.
Affected dogs often have an intermittent wheeze, which may be accompanied by bouts of coughing. They don't normally cough up any phlegm, because they swallow it before it reaches their mouth.
The wheezing can vary in pitch, and sometimes it is only heard on one part of the breathing cycle. For example, some dogs wheeze most when they breathe in, while others are noisiest when they exhale.
Bronchitis can also cause coughing, which may be worse during exercise, or when a dog is excited. These dogs also don't tolerate exercise well, and get tired more quickly than normal.
Diagnosis of chronic bronchitis in dogs
It can be difficult to work out exactly what is responsible for your dog's cough and wheeze.
The first thing to do is to localize the problem. Is the wheeze coming from his nose, his larynx or further down in his chest?
If you hold your dog's mouth shut and allow him to breathe through his nose, this will give you a lot of information. You'll be able to make sure air can get through his nose, and listen for any wheezing sounds. If all is okay there, then it's time to move further down the respiratory tract.
When your dog is lying down, put your ear over his larynx, the firm swelling in his neck. Move your ear slowly down towards his chest, and see where the noise is loudest. Finish by listening to his chest as he breathes, and see if there is any noise coming from the lung area.
This will help your vet make a list of likely diagnoses. A wheeze that originates from the nose is often associated with a foreign body such as a blade of grass, an infection or nasal mites. If it is noisier further down the neck around the pharynx, then you may be dealing with a chronic infection, or a physical abnormality such as an elongated soft palate. Lung sounds are usually due to infection or inflammation of the smaller airways.
You need to be prepared to invest a few dollars in diagnostics to find out exactly what's causing the problem. Initially, your vet will recommend some blood tests to check your dog's general health. A blood count will give good information – wheezing due to an allergy or parasites will be reflected in a higher than normal number of eosinophils, a white blood cell. Another type of white blood cell, the neutrophil, is usually increased in cases of bacterial infection.
Other diagnostic tests include x-rays, ultrasound and bronchoscopy. In this last test, your dog is given a general anesthetic and a flexible tube with a camera attached is passed into your dog's airways. This gives your veterinarian the opportunity to see exactly what is happening down there, and to collect some cell and mucus samples. This is then analyzed under the microscope. The number and type of cells, and the amount of mucus, can help reach an accurate diagnosis.
Another common procedure is a tracheal wash. This is also done while your dog is under anesthesia. A small amount of water is placed into his trachea, or windpipe, using a soft tube. This is sucked back up and the cell types are examined.
Treating chronic bronchitis in dogs
There are specific treatments for your dog's wheezing, depending on the cause. For example, if a bacterial infection is involved, antibiotics will be prescribed. Allergic bronchitis may respond to antihistamines.
Whatever the cause, there are some treatments that will help to ease the symptoms.
If your dog is carrying a little extra weight, put him on a diet. Also, walk him with a chest harness rather than a neck collar, to avoid putting pressure on his larynx and trachea.
Bronchodilators such as ventolin or bricanyl will open up the airways and allow more air to pass through. This will make breathing easier and help to stop the wheeze.
Cough suppressants are available from your veterinarian to specifically stop the coughing. This will no doubt give you all a better night's sleep. Some of these medications also work to break up mucus, and make it easier to cough up. This helps to clear the airways and make it easier to breathe.
Corticosteroids such as prednisolone and dexamethasone have a specific anti-inflammatory effect. They reduce the thickening of the airways and the increased mucus production that occurs in chronic bronchitis. These drugs need to be used carefully, because there is a risk of side effects if they are used in high doses or for long periods of time.
A nebulizer is very useful if your dog has bronchitis. You can put him in a closed room and allow him to breathe in the steam. It's also possible to put medication such as ventolin in the nebulizer, so it can be inhaled and get to the area where it is most needed. If you don't have a nebulizer, then try keeping him in the bathroom while you shower, because this too will help humidify his airways.
Dogs with severe tracheal collapse that doesn't respond to medication may be candidates for surgery. In this procedure, a plastic ring is placed around the trachea, and sutures are placed to anchor the trachea to it. This prevents any further tracheal collapse, and usually has a very good outcome.
In many cases, chronic coughing and wheezing can't actually be cured; the best you can hope for is that the symptoms are managed well, and your dog is comfortable. This often includes ongoing medication and regular veterinary check ups to make sure the treatment is still working and doesn't need adjusting.
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