Kitty Corner: Asthma and Bronchitis

 
Obstructive and allergic lung diseases affect many cats and are sometimes called “asthma,” “bronchitis,” or “bronchial asthma.”  Unfortunately, these diseases are not easily classified and probably represent a variety of lung disorders. They do share a common finding of “hyper-responsive” or “over-reactive” airways.

When the airway of a cat is sensitive to certain stimuli, exposure to these agents leads to narrowing of the airways. The inciting agents are usually direct irritants to the airways or things that provoke an allergic response in the respiratory tract. Regardless of the cause, the end-result is the same: muscle spasms in the bronchi (breathing tubes), buildup of mucus, and accumulation of cellular material. The inability to clear the bronchi of this material leaves the cat susceptible to secondary infections.

Are some cats more likely to get asthma?
Obstructive lung disease is most common in cats from two to eight years of age. Siamese cats seem to be at higher risk for developing asthma and bronchitis. Some reports indicate that it is more common in female cats. Obese and overweight cats also seem to be at greater risk for developing respiratory disorders.

What are the clinical signs?
Although "wheezing" is the most common sign of asthma in humans, in cats the primary indicator of asthma is coughing. Coughing is a significant finding since there are relatively few causes of coughing in the cat. Many cats assume a squatting position with the neck extending during these coughing episodes. Wheezing, though not typically observed by cat owners, is easily heard with the stethoscope. Any episode of open-mouth breathing in cats should be a cause for concern and you should inform your veterinarian immediately if this occurs.

What causes asthma?
There are a number of stimuli that can lead to asthma in cats, such as: 

1. Inhaled debris or irritants such as dust from cat litter, cigarette smoke, perfume or hairspray, carpet fresheners, and perfumes in laundry detergent 
2. Pollens or mold 
3. Infectious agents (viruses, bacteria) 
4. Parasites (heartworms, lungworms

How is asthma diagnosed?
Several tests may be performed to diagnose allergic lung disease in the cat.

In most cats with a history of coughing we take a chest X-ray and sometimes perform blood, urine, and fecal tests. These tests will assess the general health of the cat and may provide clues as to the underlying cause. One particular type of white blood cell, the eosinophil, is commonly found in higher than normal numbers in cats with allergies, and helps us distinguish allergies from other causes of asthma in cats. Also, in some cats, special tests will be performed on stool samples for evidence of lungworms.

• Heartworm test – This is not indicated for all cats, as heartworms are very rare in cats in the TriValley area. In areas where they are common, however, even cats that stay completely indoors are still at risk. A cat experiencing the clinical signs of asthma should be tested for feline heartworm disease in most cases.

• Feline leukemia and feline immunodeficiency virus tests – These tests are helpful in determining the overall health of the cat.

• Thoracic radiography (chest X-ray) – Characteristic changes in the lungs are common on x-rays. Also, x-rays can be suggestive of other types of heart and lung disease.

• Bronchoscopy, cytology and airway lavage (washing) – Bronchoscopy is a procedure that allows us to look down the airways of the anesthetized cat with a fiberoptic scope. After a visual examination of the airway is completed, the lining mucus of the bronchi may be sampled with a small brush. The mucus can be examined under a microscope (cytology). Finally, a small amount of sterile saline can be flushed into the airways to retrieve samples of material from deep in the lung. This material can be cultured for micro-organisms and can also be carefully studied under the microscope.

In some cases, an underlying cause for asthma cannot be identified, despite a complete and thorough diagnostic workup. Even when the underlying cause is not identified, many cats can achieve a reasonable quality of life with medical management.

How is asthma treated?
Successful management of allergic lung disease employs one or more of the following therapies.

• Avoidance – Any factors known to trigger or aggravate breathing problems should be avoided. In some cases, this may mean trying different brands of cat litter, eliminating cigarette smoke from the home, etc. The previous list (see “Causes”) details some factors that should be considered. It is important to pay close attention to environmental factors that may aggravate the condition.

• Bronchodilators – These drugs are used to open up the airway and allow the cat to move air more freely. They should be used faithfully and as directed to obtain maximum effect.

• Corticosteroids – Most cats with asthma are effectively treated with corticosteroids (“cortisone” or “steroids”). These can be administered via daily use of an inhaler, or given systemically (injections or tablets). However, use of systemic corticosteroids may create two problems. Corticosteroids can worsen secondary bacterial infections; therefore, prophylactic antibiotics are used in cases where a bacterial infection is suspected to also be present. 

Steroids have a beneficial effect on decreasing inflammation, dilating the airway, and decreasing mucus production. In many cats, they are given daily. When the cat’s temperament is a concern, long-acting injections can be given as an alternative to pills. These drugs have potential for some side effects and should not be withdrawn abruptly.

Emergency treatment may employ bronchodilators, oxygen, rapid-acting glucocorticoids, and epinephrine. If your cat has heart disease, the attending veterinarian should be advised since epinephrine is best avoided.

Will my cat recover?
Cats with obstructive lung disease are usually manageable. Sometimes a “cure” may be achieved if a specific underlying cause can be identified and treated.