Max's House

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 female cats.

respiratory_system_of_the_cat.jpg (176710 bytes)

Clinical Signs

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.

Causes

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:

1.       Inhaled debris or irritants - dust from cat litter, cigarette smoke, perfume or hairspray, carpet fresheners, and perfumes in laundry detergent

2.       Pollens or mold

3.       Infectious agents - viruses, bacteria

4.       Parasites - heartworms, lungworms


Diagnosis

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 disease.
feline_asthma2.jpg (7566 bytes)

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.

Treatment

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 condition.

  • 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 chamber 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.

  • Inhaled 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.

  • Caution:   Bronchodilators may cause arrhythmias, vasoconstriction, and systemic hypertension.  If your cat has heart disease, the attending veterinarian should be advised.

  •  Emergency 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.

Monitoring

Evaluation of 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.

Outcome and Prognosis

The 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 acceptable. 

aerokatdevice.jpg (8183 bytes)

Areochamber-Flovent.jpg (35463 bytes)

Custom-adapted Aerochamber

aeromask-2.jpg (20669 bytes)

areo+parimask.jpg (32586 bytes)

Aerochamber with Pari Mask

Aero+Cat.jpg (37091 bytes)

Extreme respiratory distress constitutes an emergency and the cat should receive immediate attention.

See: Inhalation Therapy for Airway Disease



Main Index