Feline Asthma and Bronchitis
Extreme respiratory distress constitutes an emergency and the
cat should receive immediate attention.
|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. In particular, the inability to
clear the bronchi of this material leaves the cat susceptible to secondary infections.
The cat is most stressed during expiration (forcing air out of the lungs). Difficult
expiration or breathing out is typical with obstructive lung disease. Air may
become effectively trapped in the lungs, causing them to over inflate. In some cases, this
trapping leads to development of emphysema in the cat.
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. Also, some reports indicate that it is more common in
Coughing and respiratory
distress are the most commonly reported signs with obstructive lung disease. Coughing is a
significant finding since there are relatively few causes of coughing in the cat. Also,
many cats assume a squatting position with the neck extending during these coughing
episodes. Wheezing is easily heard with the stethoscope and is sometimes so loud that it
can be heard by the owners. Occasionally, sneezing and vomiting are noted.
As mentioned above, this group of
diseases is characterized by hyper-responsive airways. The small breathing tubes (bronchi
and bronchioles) can react to a number of stimuli, such as:
Inhaled debris or irritants - dust from cat
litter, cigarette smoke, perfume or hairspray, carpet fresheners, and perfumes in laundry
Pollens or mold
Infectious agents - viruses, bacteria
Parasites - heartworms, lungworms
Several tests may be performed to diagnose allergic lung disease in the cat.
- The minimum diagnostic tests include a complete blood count (CBC), blood chemistries,
fecal exam and urinalysis.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 associated with allergic events and may provide support for a
tentative diagnosis of asthma. 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 less likely in
some parts of the country. In areas where they are common, however, even cats that stay
completely indoors are still at risk. Heartworm tests for cats are an area of intense
research interest and their reliability is improving greatly.
- 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 heartworms or other types of heart and lung
- Bronchoscopy, cytology and airway lavage (washing). Bronchoscopy is a procedure that
allows the veterinarian 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. The sediment can
be evaluated for evidence of lungworms.
In some cases, an underlying cause cannot be identified, despite a thorough diagnostic
workup. Even when the underlying cause is not identified, many cats can achieve a
reasonable quality of life with medical management.
Some owners decline the complete workup for a variety of reasons. In such cases, it may be
acceptable to treat the cat with a course of corticosteroids (cortisone or
steroids) since most asthmatic cats respond favorably to these medications
with few side-effects. However, this approach may create two problems. Corticosteroids can
worsen secondary bacterial infections; therefore, prophylactic antibiotics are reasonable
in cases where a workup cannot be performed. Cats with heartworms often cough like cats
with asthma and will respond temporarily to corticosteroids. Therefore, cats in locations
where heartworms are common in dogs may be misdiagnosed as having asthma.
Successful management of allergic
lung disease employs several therapies.
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
- The most important type of drug for
treating feline asthma is a corticosteroid such as prednisone
or prednisolone to reduce the
chronic inflammation. Steroids
have a beneficial effect on decreasing inflammation, dilating the airway, and decreasing
mucus production. The
most effective therapy for feline asthma is aerosol corticosteroid delivered by metered
dose inhalers (MDI) such as human asthmatics use. The MDI is used in
conjuction with a delivery system consisting of a mask and aerosolization chamber.
The feline system is called an
AeroKat®, The most commonly prescribed
corticosteroid inhaler is fluticasone
propionate (Flovent®) 110-220
µg/puff. An aerosolization
into which the medication is sprayed is essential so that activation of the MDI does not
need to be coordinated with inhalation. Both the OptiChamber
and the Aerochamber are equipped with one-way valve leaflets that allow
the owner to actuate the inhaler away from the cat and then apply the spacer with the mask
over the cat's face. The one-way valves also permits two or more inhalations from
one MDI actuation thus allowing the cat to receive the full dose without any loss of
medication. The AeroKat spacer is valveless, therefore actuation
must occur with the mask applied. Both the AreoChamber and OptiChamber are available
with infant or child masks and work extremely well with cats. The AreoChamber and
OptiChamber are available at most pharmacies.
corticosteroids allow the topical use of an extremely effective drug without the degree of
harmful side effects that systemic corticosteroids can induce.
Long-acting repository corticosteroid
injections can be used as an alternative to pills and aerosol therapy when owners are
unable to medicate their cat orally. Methyprednisolone (Depo-Medrol®) can
be given IM or SC every 4 to 6 weeks.
Bronchodilators are used to open up
the airway and allow the cat to move air more freely. Bronchodilators may also be added to
chronic therapy if corticosteroid administration alone does not induce a sufficient
decrease in symptoms. Bronchodilators
may also be utilized in chronic management in an attempt to decrease the dose of
corticosteroids needed to control clinical signs, especially if corticosteroid-induced
side effects (e.g., diabetes mellitus or concurrent infectious diseases) become
problematic. Methylxanthine-derivative bronchodilators
(e.g., theophylline [Theo-Dur®
tablets or Slo-Bid®
gyrocaps]) exert additional positive effects on the respiratory tract which include
inhibition of mast cell degranulation and increased strength of respiratory muscles.
may cause arrhythmias, vasoconstriction, and systemic hypertension. If
your cat has heart disease, the attending veterinarian should be advised.
Treatment In cats that present with
acute, severe respiratory distress (e.g., cyanosis and open mouth breathing), diagnostic
tests should be delayed, stress should be minimized, and an oxygen enriched environment
(oxygen cage with Fio2 of at least 40%) should be provided. Initially,
bronchodilator therapy (e.g., terbutaline 0.01 mg/kg IV, IM, or SC) should be
used to combat acute bronchoconstriction. Inhaled bronchodilator medication (e.g., albuterol)
may be used if the equipment is available and if the cat tolerates this method of
administration. Visual inspection of respiratory rate and effort during
the first hour of therapy will allow
assessment of the therapeutic response. A positive response is expected within 30 to 45
minutes, and is indicated by a decrease in respiratory frequency and effort. If the cat
does not respond favorably in that time, a repeated dose of bronchodilator medication is
warranted and a rapidly acting corticosteroid (e.g., dexamethasone 0.25 to 2 mg/kg IV or
IM) should be administered. If no response is seen to this combination of drugs, alternate
causes for dyspnea should be investigated. if the cat remains severely dyspneic,
intubation and positive pressure ventilation with 100% oxygen may be needed to facilitate
diagnostic testing, including radiography, cardiac evaluation, and respiratory tract
cytology and bacteriology. Once the cat is stable, a complete diagnostic evaluation for
feline asthma is recommended. If corticosteroids have been administered to control
respiratory distress, airway cytology may lack the classic inflammatory response and may
therefore be of diminished benefit.
clinical response to treatment is the usual and most practical means of monitoring cats
with bronchial disease. Effective therapy should eliminate or significantly minimize the
clinical signs. Repeating thoracic radiographs to compare with those taken prior to
therapy provides an objective means to evaluate the response to treatment. The diagnosis
of bronchial disease should be questioned if a significant response is not appreciated
within 1 to 2 weeks of initiating proper treatment. Ensuring that the owner has been able
to medicate the cat at home is imperative in the evaluation of clinical response to
therapy. If a cat has not responded to proper therapy and other diseases have been ruled
out, a trial of injectable methylprednisolone acetate should be considered. Measurement of
lung function, if available, would provide an
objective evaluation of both initial disease severity and response to therapy.
majority of cats with bronchial disease respond very well to appropriate therapy, yet it
should be assumed that life-long treatment may be required. Owners should realize
that a cure is unrealistic and a minimum amount of coughing will have to be considered
Aerochamber with Pari Mask
respiratory distress constitutes an emergency and the cat should receive immediate
Therapy for Airway Disease