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RESPIRATORY: FELINE ASTHMA

YVCipedia RESPIRATORY
FELINE ASTHMA

Feline asthma has many parallels to human asthma, but the two problems have not been directly compared because  the pulmonary function testing used to characterize the problem in people is not readily available for cats, even in specialty and research settings. 

Feline asthma is also sometimes called bronchial asthma, allergic bronchitis, acute bronchitis, and chronic bronchitis. Regardless of which name is used the problem involves narrowing and inflammation of the airways in the lungs. As the inflammation persists the tissues of the airways undergo metaplasia (changing from soft and supple to hard and inflexible) and hyperplasia (thickening, which further narrows the airways).

For most asthmatic cats the problem is lifelong.

CAUSE

The cause of feline asthma appears to be allergic stimulation, in particular of an inhaled nature, for example, pollen and house dust mites.

SIGNS

All of the signs of asthma can range from mild to moderate to severe, and occasionally life-threatening. The signs may come and go or be present daily. 

Coughing, loud breathing, rapid breathing, and breathing with the mouth open are common signs. Because coughing involves considerable abdominal effort for a cat, regurgitation and vomiting may also occur. Some cats with mild signs may just appear quiet and poorly groomed. 

DIAGNOSIS

With the history and physical exam we can make a tentative diagnosis, usually one that is adequate for beginning asthma treatment. 

It is very important to note, however, that there is no test that will confirm the diagnosis with 100% certainty, and there are other cat problems that have the same signs as asthma. Parasites, bacterial infections, and heart disease are examples of such problems. 

With this in mind, diagnostic testing is still usually a very good idea. X-rays are vital and blood and fecal testing may be as well. Bronchoscopy (examining the airway with our endoscope) and bronchoalveolar lavage (flushing some sterile wash solution into the airways, removing it, and using the sample for bacterial culture and microscopic exam of the cells obtained) will add a lot of useful information. 

TREATMENT

Cats having a severe asthmatic crisis have to be hospitalized for oxygen therapy, injectable cortisone and bronchodilators, and constant monitoring until they are stable.

For long-term management there are two primary options, cortisone and bronchodilators. In my experience cortisone has been very effective and bronchodilators have been minimally effective, so I will begin long-term management of most asthmatic cats with cortisone alone, and add in a bronchodilator if / when the cortisone is not working as well as we want. 

There are three dose forms of cortisone available for long-term management of feline asthma: long-acting injections, oral medication, and inhalant medication. A fourth management strategy is to use some combination of these three dose forms. 

Cortisone has some serious potential side effects, including suppression of the immune system and diabetes. Cats are very tolerant of high doses of cortisone, however, so serious side effects are possible but uncommon. Also, please remember that cortisone is by far the most effective drug for controlling feline asthma, and this problem is, at the very least, significantly uncomfortable, at worst, life-threatening. 

The inflammation in the lungs that occurs with feline asthma continues even when the patient stops showing signs of trouble breathing. For this reason, I will usually continue treatment for a minimum of one to two months after the initial episode. 

LONG-ACTING CORTISONE INJECTIONS  At YVC  These injections are always given by a doctor following an examination of the cat and discussion with the owner. One injection typically lasts for 4 to 8 weeks; the injection is repeated if / when the patient begins to show signs again. The need for repeat injections varies dramatically from cat to cat: some cats will have one episode of asthma and never have another; some cats have signs seasonally; some cats have signs again as soon as an injection starts to wear off. If an injection lasts  4 to 8 weeks, the cost to the client is currently about $1.40 to $2.80 per day (not including the cost of diagnostic testing). The risk of side effects is small, but somewhat higher than the risk with oral cortisone. Occasional long-acting cortisone injections are the most effective treatment, largely because it is not necessary to medicate the cat at home. 

ORAL CORTISONE  When the owner and I decide on this treatment option, I will most often follow a schedule of once daily for 1 month, once every other day for 1 month, once every third day for one month, and, if the patient has shown no signs of relapse, then try her off of medication. I will return to once daily use if necessary. Cats that present with severe signs will receive a cortisone injection and begin tablets about 2 weeks later. The cost to the client is $.25 to $.50 per day for plain tablets, and up to $2.00 or more per day for specially compounded oral cortisone dose forms such as chewable tabs and flavored liquids. Oral cortisone is not as effective as occasional long-acting injections. There is a somewhat smaller risk of side effects compared to injections. An obvious, potentially significant disadvantage is the need to medicate the cat orally on a daily to every-other day basis for an extended period of time. 

INHALED CORTISONE  The same asthma inhalers that asthmatic people use can be used for treatment of asthmatic cats. A small, handheld device known as an Aerokat holds the inhaler at one end, the “puff” of medication in a middle chamber, and a mask for placement over the cat’s face at the other end. Compared to injectable and oral cortisone, inhaled cortisone has one great advantage: it is very minimally absorbed from the lungs into the rest of the body, so the risk of side effects is almost zero. Inhalers have some significant disadvantages, though:

- One inhaler currently costs almost $500 (There are some less-costly inhalers but they are far less likely to work.) The cost per puff is about $4.10. Most cats need somewhere between 1 puff every other day to 2 puffs per day, making the cost per day $2.05 to $8.20. An Aerokat at a cost of $50 - $70, can be used indefinitely. 

- Training a cat to accept a mask placed over it’s nose and mouth and held there long enough for 8 to 10 breaths to be taken (especially when it is having trouble breathing) can be a very time-consuming (weeks), difficult challenge. (I recommend watching the Aerokat training video on YouTube before purchasing one, and before purchasing an inhaler.)

- More cats have asthmatic relapses when managed long-term with an inhaler, necessitating simultaneous use of oral and/or injectable cortisone.

OTHER TREATMENTS  Other treatments, with a few exceptions, have not shown much promise for effectively treating asthma; in particular, antihistamines and medications other than cortisone that suppress the immune system do not work well or at all. Some exceptions: 

Worm-type parasites are rarely the cause of asthma signs in cats, but it is easy, safe and relatively inexpensive to administer a dewormer, so I will usually do this for asthmatic cats that have an indoor / outdoor lifestyle. 

Another uncommon cause of asthma signs in cats is infection with Mycoplasma, a bug that straddles the line between being a bacteria and being a virus. It can be challenging to definitively diagnose a Mycoplasma infection, so if my degree of suspicion is high that a particular patient might have this infection I will recommend treatment, which is 4 weeks of a daily oral antibiotic.

Omega-3 fatty acids, also known as fish oil, have been shown with recent research to have some significant effect blunting the lung inflammation associated with asthma. Since they are relatively inexpensive, safe, and usually readily accepted along with food, I will usually recommend using fish oil as a long-term daily supplement.

OTHER ASPECTS OF LONG-TERM ASTHMA MANAGEMENT

Home control measures must be instituted. It is very important to minimize or eliminate potential asthma triggers like cigarette smoke, fireplace and wood stove smoke, perfumes and other fragrances, and dusty cat litter. Air filters and air conditioners can help, too. 

I recommend that asthmatic cats be examined at regular intervals, even though they may not be showing signs of trouble. A typical schedule that I will advise is a progress exam 2 weeks after the initial treatment, 1 month later, then once every 3 to 6 months. At each visit I will do an exam and discuss the patient with the owner; occasionally I will recommend repeating an x-ray or other diagnostic test. 

PROGNOSIS
The long-term outlook for most asthmatic cats is good to excellent when long-term management is used. 

Peter Smith DVM
Yarmouth Veterinary Center
2014

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