Ron Hines DVM PhD 5/29/2005

Asthma in cats is a chronic inflammation of the small passageways of the lungs called bronchioles. In asthma, these passages thicken, and collapse when the cat inhales making it difficult for the pet to catch its breath. All degrees of asthma exist. In severe cases, coughing, wheezing and exercise intolerance occur. In these cases, large numbers of bronchioles plug with mucus and the smooth muscle that surrounds the airways go into spasm restricting breathing. Other cats have only a mild cough or high-pitched wheeze that comes and goes. It is estimated that one percent of all cats suffer from asthma. The incidence of the disease is highest in Siamese cats.

The chronic bronchitis of feline asthma usually first occurs between the ages of two and six. It starts as a slight cough and mild respiratory distress interspersed with long periods during which the cat is normal. These early signs are often overlooked.

Cats in the midst of an acute asthma attack have very hard time breathing. They assume a praying position and concentrate on obtaining the air they need in deliberate breaths. These breaths are deep, labored and abdominal. Sometimes they will vomit. A severe asthma attack can be life threatening.

Triggers:
Episodes of asthma are triggered by allergens or stress. Some common allergens are grass and tree pollens, smoke, fumes, cigarettes, dust, and aerosols of various sorts such as perfumes, deodorants and flea spray. When these cats contract bacterial, mycoplasmal or viral respiratory disease the problem becomes much worse.

Diagnosis:
Cases that are mild and in which a dry hacking cough occurs are sometimes misinterpreted as hairballs. During severe attacks, however, the amount of effort expended by the cat in simply getting a breath is startling. These cats often must breathe with their mouth open. Only heart disease, pneumonia or diaphragmatic hernia mimic an asthma attack. When I Listen to the lungs of these cats with a stethoscope during an attack I hear cracking and whistling sounds. To be sure of my diagnosis I take an x-ray image of the cat’s chest. One must be very gentle in restraining the cat for the photograph so it does not faint. When I am convinced that the heart silhouette is normal and the diaphragm is intact I look for telltale over-inflated lungs and lucities that represent trapped air in the lungs. The patterns we see are called “doughnuts”. The outline of the bronchiolar “tree” is also thickened and accentuated. If the x-rays are not diagnostic saline can be used to wash cells from deep within the lungs for microscopic examination (trans-tracheal wash, bronchial wash, or broncho-alveolar lavage). The presence of large numbers of eosinophil white blood cells are characteristic of the disease.

Although I have never encountered a case of heartworms in a cat, the signs of heartworms are said to mimic feline asthma. So in some cases a heartworm blood test is appropriate.

Treatment:
Asthma in cats can be treated successfully but not cured. We rely on two different drugs during an acute asthma attack.

Bronchodilators such as aminophylline (3mg/lb, bid) relax the muscles that surround the airways. This medicine has an immediate effect in dilating the bronchioles and easing respiration. Another human bronchodilator, Apo-Salvent® has been used successfully in cats.

Corticosteroid anti-inflammatory drugs are used to decrease the inflammatory symptoms of feline asthma. Administering the inhaled steroid, fluticasone propionate, or Flovent®. works quite well in cats. The advantage of using inhaled Flovent is that the systemic side effects of oral corticosteroids avoided. A more traditional method of treatment utilizes the oral corticosteroids, prednisone or prednisolone administered at 0.5-1.0 mg/lb. body weight twice a day for 10-14 days and then slowly reduced over a period of three to four months. Some veterinarians use an injectable form of the drug, methylprednisolone acetate (10-20mg/cat) every two to four weeks when the cat will not accept pills.

Terbutaline is a bronchodilator that relaxes bronchiole smooth muscle. Although it is given to humans by inhalation we inject it subcutaneously in cats at 0.005mg/lb.

My preference is to administer as much medication by inhalation as possible and as little as I can orally or by injection. A mask and spacer system, called AeroKat® (http://wwwaerokat.com), is marketed to adapt human inhalers and puffers for use in cats. This system is similar to the mask and spacer system used to treat human babies and small children.

Some cats benefit from long-term cyproheptadine (Periactin) administration (2mg twice a day). Cyproheptadine is an antihistamine.

Experimentally the anticancer agent, cyclosporine, given at 5mg/lb twice a day has benefited some cases.

Some cats only need medicines intermittently when the condition flares up but some do better on low doses of medicine continuously. Cats tend to have less serious side effects from long term corticosteroid administration than people do but care must be taken to prevent them from becoming obese.

Prevention:
Try to remove as many triggers as possible from the cat’s environment. Remember that it is unusual for one single item to be responsible for all of the cat’s symptoms. Try to remove suspected items one at a time. If you suspect that a certain brand of cat litter is one of the causes, replace it for two or three weeks with shredded newspaper or dust-free sand. If the cat’s condition improves you can try new brands of cat litter later.

Change your air-conditioning and heating filters frequently or purchasing a high-efficiency filter. Avoid exposing the cat to cigarette or fireplace smoke and minimize the use of aerosols, sprays and perfumes around the house. Any activity that you associate with asthma attacks should be avoided. Sometimes it is cold outdoor temperatures that trigger an attack. If this is so keep your cat indoors in the winter.

Recently, an organism call Bartonella has been implicated in chronic respiratory infections in cats. The diagnosis of Bartonella infection is made using a laboratory test called the Wesern Blot. When cats are positive for this organism it can be sucessfully treated using azithromycin, doxycycline or rifampin.

Iit is quite common for cats to exhibit asthma-like symptoms when they are infected with canine heartworms. Only a few heartworms can cause these signs because the hearts of cats are very small. So it is wise to perform an occult heartworm test on a blood sample from all cats with asthma-like symptoms to rule out this disease.

Some of my clients have had good results administering 110 micrograms(mcg) of Flovent (flutacasone propionate) aerosol inhailer using an Aerokat Feline Aerosol Chamber twice a day. They estimate that 0.2-0.5mcg of the puff actually ends up medicating the bronchioles. Delivering this potent corticosteroid directly to the lungs in this way minimizes the systemic side effects of corticosteroid medications. It takes up to two weeks for the full beneficial effect of this medication to show effect.

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