IMPORTANT NEWS - The Cat Clinic is Moving in 2024 - Click here to read more

Cat health

Asthma/bronchitis - airway disease

Feline chronic small airway disease comprises a spectrum of conditions involving the small airways (bronchioles) within the lungs. The condition is also known as chronic bronchitis, allergic airway disease, allergic bronchitis and asthma.

Some cases bear similarities to asthma in humans, hence it is frequently known as 'feline asthma', however the majority of cases are not proven to have an allergic cause. Inhalation of irritants such as pollens, cigarette smoke, dust and household cleaning sprays are sometimes implicated.

The airways respond to an irritant by contraction of the bronchial smooth muscle in order to prevent the irritant from moving deeper into the lung, the production of mucus to trap the irritant and initiation of a cough to expel the irritant. Contraction of the smooth muscle, mucus production and airway inflammation all contribute to narrowing of the airways which results in difficulty breathing.

Can any cats develop the condition?

Cats of any age, breed or sex can develop chronic airway disease, however young to middle aged cats are most frequently affected. Siamese and Burmese cats appear to be particularly predisposed.

What clinical signs do cats show?

Signs vary from chronic coughing and/or wheezing to the development of sudden onset laboured breathing without any prior clinical signs. An increase in respiratory rate (>30-40 breaths per minute) or effort (particularly expiratory effort - breathing out) may also be noticed. Symptoms may come and go or may be so mild that they go unnoticed by owners for sometime.

How is it diagnosed?

Other diseases such as bacterial infections, foreign bodies, heart disease, airway parasites and lung cancer can present with similar clinical signs and therefore these  need to be eliminated before a diagnosis of chronic small airway disease can be made.

X-rays of the chest are required and usually demonstrate evidence of thickening of the bronchial (small airways) walls and air trapping within the airways. Air trapping occurs because when the airways have constricted, air cannot be exhaled. The lungs therefore appear larger than normal on X-rays, as they are over-inflated. The diaphragm may seem flattened due to this over-inflation. Not all cats however will have these changes, and X-rays can appear normal.

Another diagnostic technique that can be useful is bronchoscopy. This is a technique whereby an endoscope is passed into the airways to enable visualisation of the airways. Excessive mucus, roughening and reddening of the airways may be seen in cats with chronic airway disease, although again the gross appearance can be normal in some cats. Very small endoscopes are required to examine the airways of cats and therefore this procedure is most frequently carried out at specialist centres.

Airway washes (bronchoalveolar lavage or BAL) can also be collected and examined under a microscope for the presence of inflammatory cells, bacteria and cancer cells. These washes can also be cultured to assess whether bacteria are present within the lungs. Lots of inflammatory cells are usually evident in washes taken from cats with chronic small airway disease.

How is small airway disease treated?

1. Anti-inflammatories  - Reducing the inflammation within the airways is the most important part of treatment. Corticosteroids are potent anti-inflammatories that are used to achieve this. This treatment can be administered in different ways:

  • Systemically - in the form of tablets, liquids, pastes or injections
    In the past corticosteroid tablets or injections have been used to treat the condition. These drugs can result in side effects such as increases in appetite and thirst, weight gain, diabetes mellitus, and thin fragile skin.
  • Inhalational - More recently inhaled steroids have been used for treatment, with the big advantage that the drug is delivered directly to the lungs where it is required, but is not absorbed into the body therefore avoiding side effects with long-term use. A special 'mask and spacer' has been designed for the delivery of inhaled drugs to cats (see additional handout “Spacers for inhaled medications”). Cats tolerate the procedure surprisingly well and with the majority of cats it is easier than administering tablets.
  • Other stronger immune modulating drugs can be of benefit in some patients.

2. Bronchodilators - Drugs to help dilate the airways are usually used in conjunction with corticosteroids. These can also be given in the form of oral or injectable medication  or by inhalational treatment.
3. Mucolytics  - In some cats excessive production of mucus can be a problem. Adding a mucolytic (eg. Mucodeine) can help in these cases.
4. Reducing exposure to irritants - Some actions can be taken in the home to reduce the severity of the signs, namely avoidance of smoking and the use of household sprays around the cat. Using a low dust type of litter may also help.

What is the prognosis?

The prognosis for this condition depends on the severity of the disease and on the time delay before treatment is initiated. Whilst the majority of cats respond well to treatment, acute severe attacks can prove fatal if treatment is not initiated promptly. In addition, if the condition is chronic and treatment has been delayed, irreversible fibrotic changes within the airways can occur.

Copyright © 2018 The Cat Clinic
homeplus linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram