July 05, 2013
As many of us endure a significant flare-up of seasonal allergies this time of year, we may also see these problems in our pets. In fact, we do see a significant number of cats with signs of asthma that may flare up seasonally similarly to that seen in people! Asthma is a recurrent compromise of a cat’s respiratory function that features a constriction (narrowing) of the lower airways in the lungs. Initially, excess mucus forms in the airways, followed by swelling and inflammation of the airways. Eventually the small muscles lining the airway walls spasm and cause narrowing of the airways. Signs of an asthma episode can include the classic wheezing we think of in people, but in many cases, cats may have a low-grade cough long before they have an acute crisis that involves wheezing and respiratory distress. Some cats may simply show a decreased activity level or may “pant” with little or no exertion; severe cases often show contraction of the abdominal muscles to help move air in and out of the lungs, and the breaths are generally very shallow. Unfortunately, a cat with asthma may progress from very mild signs to an acute crisis very quickly, and these crises can be potentially life-threatening. Cats with any sign of respiratory change or abnormality do need to be examined by a veterinarian!
We’re not sure if feline asthma and human asthma are exactly the same – much research is being done regarding this question; in fact, medical research done to investigate human asthma often uses the cat as a model. Fortunately, some of the research done to benefit human asthma patients has helped our feline friends, too! However, we do suspect that cats with asthma probably have abnormal airways even when they don’t show signs of the disease.
One case that stands out to me is Jason, a 13 year old cat, who first came in with mild coughing in January 2013. He came back for further diagnostic testing including an echocardiogram and chest X-rays to determine if the cough was related to his heart disease or something else. Jason’s X-rays showed changes consistent with asthma. X-rays of an asthma patient often show more prominent lower airways, as the inflammation and mucus accumulation allows them to be more easily seen. Sometimes we see that the lungs appear over-inflated as well, since the narrowed airways tend to trap more air in the lungs than normal. These thickened airways may look like “doughnuts” when viewed on end or “traintracks” when viewed from the side on the X-rays. Unfortunately, however, some cats with severe airway disease can have normal chest X-rays.
Jason was started on medications to help control the inflammation in his lungs and has had regular examinations and radiographs to ensure the condition is not worsening. While asthma is treatable, it is not curable, and he will be on medication for life.
Other tests that can help us diagnose asthma are tracheal washes and bronchoscopy. Tracheal washes involve collection of cells from the lower airways by lightly sedating the patient and using a tube to flush and retrieve sterile saline from the airways. Bronchoscopy involves the use of an endoscope (a fiberoptic tube that can be passed down the airways) to visualize the airways and collect cells or even tiny tissue samples; it is done under general anesthesia. Obviously, these procedures are generally done once an asthma patient is stable, and they do require intense monitoring; bronchoscopy is usually done by a specialist due to the specialized nature of the procedure and the equipment.
Unfortunately, however, sometimes these advanced diagnostic tests may not yield a definitive diagnosis, as not every asthmatic cat has an increase in inflammatory cells (eosinophils) within the airway that could be collected. Also, the inflammatory cells we are looking for can occur with other conditions of the lungs like lungworms and heartworms. These conditions can cause signs that look identical to asthma. Cats with signs of asthma may be tested for heartworms by blood test and may be dewormed for lungworms to account for these other possible causes of airway disease.
Sometimes we decide to use the cat’s response to treatment as a diagnostic test, since we know that asthmatic changes to the lungs are generally reversible with treatment. Treatments in an emergency situation can involve the use of epinephrine or bronchodilators given by injection to try to reverse the airway constriction quickly. Many patients will be placed on oxygen until their breathing is stabilized, and great care will be taken not to stress these kitties, as the condition can worsen very quickly with stress. Injectable steroids (similar to cortisone) are also often given to quickly decrease the inflammatory reaction within the airways.
There are several options for treating asthmatic patients and treatments are based on the severity of the condition and the method of treatment the patient will tolerate. As with people who suffer from asthma, removal of irritants in the air is always helpful in preventing flare-ups. These irritants include cigarette smoke, dusty cat litter, aerosols, and powdered cleaning products. Using a low-dust cat litter and changing the air filter monthly are important preventive measures for an asthmatic cat.
However, it’s important to remember that cats rarely cough or pant. If you notice your cat panting (breathing with its mouth open), coughing, breathing with an increased abdominal effort, or wheezing, you should contact your veterinarian immediately.
Dr. Michelle Ford is a veterinarian at Care First Animal Hospital at Glenwood. Because of her son’s allergies to animals she does not have any pets and therefore lives vicariously through her wonderful clients’ pets!
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