Cats are often diagnosed as having ‘feline asthma’. While being a common condition the actual cause is somewhat uncertain.
The terms ‘feline asthma’ and ‘chronic bronchitis’ are often used interchangeably in cats and are used to describe chronic disease of the small airways (bronchioles) within the lungs. Other terms describing the same syndrome are ‘allergic airway disease’ and ‘allergic bronchitis’.
In human medicine, chronic bronchitis and asthma are two separate conditions (although some people have both). Asthma is usually an allergic condition where exposure to a trigger causes inflammation and narrowing of the airways. With chronic bronchitis, there is also inflammation of the airways but this is caused mainly by irritation. Exposure to tobacco smoke and other environmental pollutants is the most common cause of chronic bronchitis.
It is assumed that most cats which develop signs of small airway disease have a condition similar to asthma in humans, but the exact cause in most cases remains uncertain.
What happens in asthma or chronic bronchitis
Asthma is a condition where the small airways in the lungs over-react to the presence of a stimulus – an irritant or an allergen. This will provoke an inflammatory response and increase mucus production in the airway (making breathing more difficult), but importantly in asthma, the reaction causes contraction of the small muscles around the airways causing them to narrow markedly. This too causes difficulty breathing.
In chronic bronchitis, the underlying problem is irritation from small particles being breathed in from the air. Smoking is the major cause in humans, and the breathing in of smoke, fumes or other irritants causes inflammation of the small airways and stimulates increased production of mucus. It is a combination of the inflammation and mucus production that causes narrowing of the airways and difficulty breathing. There may be some constriction of the muscles around the airway, but this is not a major part of the disease.
What are the clinical signs of cats with asthma or chronic bronchitis?
The clinical signs of asthma or chronic bronchitis vary in severity between individuals. In addition, the signs may be either persistent or episodic. Typical signs include:
- Persistent coughing (often bouts of coughing)
- Laboured and/or fast breathing
- Noisy breathing and wheezing
- Difficulty in breathing
These signs are seen in both cases of asthma and chronic bronchitis. In some cats, further signs may develop that are strongly suggestive of asthma – in these cats there is a very sudden onset of severe breathing difficulty and wheezing, with cats often having great difficulty in catching their breath. This appears to be similar to acute severe asthma in humans (previously termed ‘status asthmaticus’) and will respond rapidly to therapy with drugs that relax the muscles around the small airways and so dilate them (bronchodilators), making breathing easier. The response to bronchodilators in these cats strongly suggests there is reversible constriction of the airways which a characteristic of asthma.
Which cats develop asthma or chronic bronchitis?
Cats of any age, breed or sex can develop chronic airway disease. Most affected cats are adults, and typically 6-9 years of age, but signs can start in young cats or elderly cats as well. There is also a marked breed predisposition among Siamese and related breeds, strongly suggesting an inherited component to the disease in at least some cats.
How is asthma or chronic bronchitis diagnosed?
Cats with other diseases such as bacterial infections, pneumonia, foreign bodies, heart disease, airway parasites and lung cancer can present with similar clinical signs to asthma or chronic bronchitis so further investigations are usually needed to confirm a diagnosis. These may include:
- Blood tests
- X-rays of the chest to look for typical abnormalities in the lungs
- Bronchoscopy – passing a small endoscope (camera) down into the lungs to look at the small airways
- Airway washes (bronchial or bronchoalveolar lavage) – this is a procedure performed under an anaesthetic that allows cells and fluid from the small airways to be collected and then examined for the presence of inflammatory cells, bacteria, cancer cells and other changes.
Some or all of these investigations may be needed in some cases. These investigations help to rule out other diseases. Some tests such as airway washes may help to differentiate between asthma and chronic bronchitis but definitive criteria are lacking. Washes are also helpful to look for secondary problems such as lung infections.
How is asthma or chronic bronchitis treated?
Although in theory, if chronic bronchitis and asthma could be reliably distinguished this may affect how treatment is targeted, in practice, both are currently treated in the same way.
Generally, any secondary infections (with bacteria or mycoplasmas) should be identified and treated, and any predisposing or exacerbating causes identified and removed if possible. This would include:
- Managing any obesity (as this can worsen breathing difficulties)
- Identifying any potential irritants or allergens in the house, for example: pollens, use of perfumes or sprays, use of dusty cat litter, smoking in the house etc
- In some cats the disease may be seasonal or may occur only when the cat is in certain rooms. In these situations, it may be possible to track down an irritant or allergen that triggers the disease with careful investigations
In most cats, specific trigger factors cannot be identified (or cannot be avoided) and so symptomatic treatment will be required. This is mainly based around anti-inflammatory and bronchodilator therapy:
- Anti-inflammatory drugs – these are important in most cases to reduce the inflammatory component of the disease. Corticosteroids (glucocorticoids) such as prednisolone are potent anti-inflammatories that are used to achieve this. Treatment can be administered in different ways:
- In tablet or liquid form that is given by mouth – usually daily or alternate day therapy is needed, but with long-term therapy often only a low dose will be needed to maintain control of signs
- By injection – products given by injection may be short-acting (eg, 1-3 days), or long-acting (some injections may last up to 3-6 weeks)
- By inhalation – metered-dose inhalers (MDIs) used to treat human asthma that contain steroids (such as beclometasone or fluticasone) can also be used in cats. To administer these to cats a ‘spacer’ device is used (just as in human babies and young children) with a face mask. Many cats actually tolerate this extremely well and treatment can be given once or twice a day this way. The big advantage with this is that the steroid can be delivered directly to the lungs, and absorption into the body can be minimised (to reduce the risk of side effects with long-term use).
- Bronchodilator therapy – this is the use of drugs that relax the small muscles around the airways and help them to dilate. These are usually used along with corticosteroids (see above). They can also be given in three ways:
- Tablets or liquid given by mouth – drugs such as terbutaline act as specific bronchodilators in cats and can be valuable. The methylxanthine class of drugs (such as theophylline) are sometimes used in other animals as bronchodilators, but they appear to be less useful and less effective in cats
- Injections – short-acting injectable bronchodilators are available (including terbutaline) and as these act quickly (especially if given intravenously) they may be useful in emergency situations
- By inhalation – in exactly the same way as human steroid MDIs can be used to treat cats, so too can human bronchodilator MDIs. Inhaled bronchodilators may be rapid in onset but relatively short-lasting (such as salbutamol which may have to be given every few hours), or long-acting such as salmeterol that may need to be given once or twice a day. As with inhaled steroids, the advantage of inhaled bronchodilators is that the drug is delivered directly to the lungs where it is needed.
- Other drugs – some other drugs are used on occasions in cats – different types of anti-inflammatory drugs or drugs designed to block an allergic response, but generally their value is uncertain and unproven
How are inhaled drugs administered to a cat?
A special ‘spacer’ has been designed for the delivery of inhalational drugs to cats (see www.aerokat.com). One end of the Aerokat spacer is specially made to allow a human metered-dose inhaler (MDI) to fit and deliver a dose of medication into the chamber (spacer). At the other end a face mask is attached with a valve that allows the cat to breathe in the medication from the chamber. One to two puffs (according to your vet’s instructions) of the MDI are administered into the chamber and then the face mask is held gently over the cat’s face so it can breathe in the medication for typically 10-15 seconds. This is usually performed twice daily. Most cats tolerate the procedure very well and with a little practice, it is much easier than administering tablets.
Using an inhaler to treat feline asthma
Asthma or chronic bronchitis in cats is often treated with a combination of anti-inflammatory drugs (steroids) and bronchodilator drugs (to make breathing easier). Traditionally these medications have been given by mouth (tablets or liquids), or by injection. However, just as inhaled drugs are used to treat most humans with these conditions, so too inhaled drugs can be used to treat cats. Inhaled medications are delivered through a ‘metered dose inhaler’ – in adult humans, we learn to breathe in at the same time that a dose of the drug is delivered, so that the drug reaches the lungs.
This cannot be achieved in babies and young children, so in this situation, a ‘spacer’ device is used – a chamber into which the dose of drug is delivered and then the baby or child breathes in the air (and the drug) from the chamber by using a face mask fitted to it. Inhaled therapy can be delivered to cats in exactly the same way.
Spacer devices (chambers) for use with cats
A special spacer device (or chamber) will need to be used for cats. It is possible to adapt some spacers designed for use in babies to be used in cats, but these are not ideal. In particular, some will have valves in them which will make it difficult for the cat to inhale the medication from the chamber, and it will often be difficult to fit an appropriate size face mask for a cat onto a human spacer device.
Spacer devices have now been made specifically for though (e.g., the Aerokat – www.aerokat.com) which are easy to handle and have a small face mask suitable for use with cats. If cared for properly, one of these devices will last for years.
Get your cat used to the spacer device first
Before you start to use the spacer to deliver inhaled drugs to your cat, it is a good idea to simply get them used to using the spacer and face mask first, without any drugs. Do this gradually and try to make it fun – play with your cat and spend time with them, ideally get them used to the mask and spacer immediately before feeding them.
At first, you may just use the mask, and get the cat used to having this held on the face – just for 2-3 seconds at first, but as your cat gets used to it lengthen the time to 20-30 seconds. Once your cat is used to the mask, try attaching the small chamber as well, and repeat the process until your cat is used to having the whole apparatus held up to the face and will breathe through the chamber. Once your cat is comfortable with this, you are ready to start using the chamber to deliver the drugs.
Administering drugs through the inhaler
Administering some human medications can be dangerous, so you should only ever use drugs with an inhaler that have been specifically prescribed by your vet. To administer a dose of inhaled therapy to a patient, first ensure the cat is accustomed to using the inhaler – see above – and then follow these steps:
- Shake the metered dose inhaler (MDI) according to the instructions supplied with it before each use
- Attach the MDI to the spacer unit
- Actuate a dose, by pressing down the MDI, to deliver a single dose into the chamber
- Immediately hold the unit over the cat’s face with the mask fitting snuggly and allow the cat to take 10-15 breaths (usually 10-20 seconds)
If your vet has told you to give deliver two ‘puffs’ of treatment, or to use two different drugs, these should be given as two separate administrations (ie, follow steps 1 to 4 and then repeat). Never give two puffs (of the same or different drugs) into the chamber at the same time as this is much less effective.
What bronchodilators are commonly used?
Bronchodilators such as salbutamol and albuterol are often used. These have a rapid speed of onset (5–10 minutes) but a relatively short duration of action (2–4 hours) meaning they are suitable for use ‘as needed’ including in emergency situations.
Some longer-acting bronchodilators (eg, salmeterol – onset of action 15–30 minutes, duration greater than 12 hours) are available and can be helpful given twice daily in those cats benefiting from long-term bronchodilator therapy.
What steroids are commonly used?
Fluticasone propionate given twice daily is a commonly recommended glucocorticoid, as it has high potency but is generally not absorbed well into the blood and so largely avoids unwanted side effects. Cheaper glucocorticoids (eg, beclomethasone dipropionate) can also be used but there may be a higher risk of side effects with long-term use. Often higher doses of steroids (higher strength MDIs) are used initially in a cat with asthma or bronchitis, and the dose (strength) may be decreased over time with a good response.
What is the prognosis for feline asthma or chronic bronchitis?
The prognosis for these conditions depends mainly on the severity of the disease. In most cases, appropriate therapy will dramatically improve clinical signs and quality of life for the cat, but life-long therapy may be required and acute severe attacks can prove fatal if treatment is not initiated promptly. In some cases, there will be ongoing damage to the lungs and this may result in irreversible fibrotic changes within the lungs in some cases, that can eventually prove fatal.