by Jennifer Chaitman, VMD, ACVIM (Internal Medicine) and Eveline Han, ACVIM (Internal Medicine)
Feline asthma is also called feline allergic bronchitis. This disease is most often due to allergies to inhaled substances (such as dust, pollens, grasses, cigarette smoke, household cleaners, etc.), but can also be due to food allergies. Reaction to allergens causes inflammation, excessive production of mucus, abnormal thickening of the muscles in the walls of the airway and spasming and narrowing of the airway. Typical signs include cough, increased respiratory rate, and in severe cases respiratory distress. In many cases these signs are episodic.
The diagnosis of asthma is usually suspected based on history and clinical signs, but thoracic radiographs (chest "x-rays") are important to rule out other causes of cough. In addition, other tests such as an endotracheal wash, or less commonly bronchoscopy are recommended to evaluate the fluid in the airway and to assess for concurrent problems such as infection (bacteria or mycoplasma). In addition, other diseases can mimic asthma (such as lungworm infection and tumor) and these tests are important to rule out these potential diseases. However, by far, asthma is the most common cause of cough in the cat.
Treatment of asthma involves elimination of the underlying cause (allergy), if possible, and medication to help decrease the inflammation, secretions and "reactivity" of the airway. Environmental control at home is often very important to help decrease exposure to potential allergens. Some recommendations include:
--using minimally dusty cat litter (Yesterday's News is a litter made from recycled paper that is not dusty at all);
--not using aerosols or carpet cleaning products in the environment
--not exposing the pet to cigarette or cigar smoke
--minimizing exposure to wool blankets or carpeting
In addition, keeping the environment cool, and minimizing stress can be very helpful. You can also try using a HEPA filter in your home (if possible).
In the majority of cases, environmental control is not enough and cats require medical therapy. The basic treatment regimen for feline asthma includes steroid therapy to decrease inflammation, and bronchodilators (terbutaline or theophylline/aminophylline) which help open the airways. Some cats require very long and often life-long courses of steroid therapy to help control their disease. The goal is to wean down to the lowest effective dose possible of the prednisone, since chronic steroid therapy has many unwelcome side effects, including the development of diabetes mellitus. In cases where chronic high doses of steroids are needed to control symptoms, inhaled steroids can be used. Inhaled steroids are effective in most cases but are much more expensive than oral steroids. A special face mask and delivery chamber is used and the pet has to become acclimated to the face mask. Some pets will not tolerate this. The web site fritzthebrave.com has feline asthma information as well as pictures and videos demonstrating inhaled steroid administration.
Other medications are sometimes prescribed that may be beneficial in cats with refractory asthma or may help reduce the amount of prednisone. Zafirlukast and montelukast (leukotriene antagonists) inhibit some of the substances that cause inflammation, cyproheptadine (periactin) is an antihistamine with other anti-inflammatory properties, cyclosporine is a drug used to suppress the immune response that works in a way a bit different than prednisone. Antibiotics are sometimes recommended due to the increased risk of secondary bacterial infection, and in many cases mycoplasma infection. Also, inhalant therapy using a nebulizer to deliver bronchodilators may be helpful for some cats, especially during an acute "asthma attack".
Lastly, although infrequently investigated in the past, there is some evidence that a food trial ("hypoallergenic diet") may help some cats with asthma. In addition, other cats may respond to hyposensitization vaccines ("allergy shots") which are developed based on the results of a blood test to look for antibodies to different allergens, and less commonly based on an intradermal allergy skin test. A food trial may take over 10 weeks to have an effect, and allergy shots may take as long as a year to have an effect, and there are certainly a fair number of cats that may not respond to either therapy.