Asthma, also known as chronic obstructive pulmonary disease (COPD), or chronic allergic bronchitis is common in cats and small dogs. The cause of the disease is allergic stimulation leading to inflammation and subsequent narrowing of the bronchi and bronchioles (tubular structures that move air in and out of the lungs), resulting in difficulty breathing. All degrees of asthma exist. In severe cases, coughing, wheezing and exercise intolerance, fainting and even sudden death occur. In these cases, large numbers of bronchioles plug with mucus and the smooth muscle that surrounds the airways go into spasm restricting breathing. Other dogs and cats have only a mild cough or high-pitched wheeze that comes and goes. It is estimated that one percent of all cats suffer from asthma. The incidence of the disease seems to be highest in Siamese cats.
In dogs, asthma usually presents as a chronic, non-productive cough and/or periodic wheezing. The cough is often more pronounced at night. In cats, the most common symptoms are panting (this is abnormal in cats), periodic wheezing episodes, or, in severe cases, turning blue of the tongue, passing out, and even sudden death.
Episodes of asthma are triggered by allergens or stress. Some common allergens are grass and tree pollens, smoke, fumes, cigarettes, dust, and aerosols of various sorts such as perfumes, deodorants and flea spray. When susceptible dogs and cats contract bacterial, or viral respiratory disease the problem becomes considerably worse.
Asthma is diagnosed by physical examination and chest x-rays. Taking the x-ray iteslf can be dangerous in an of itself, as the stress of being positioned for the x-ray can send the patient into a crisis. This is most significant in cats. Therefore, I always keep an oxygen machine close by as a precaution.
The typical chest x-ray of dogs and cats affected with asthma, is what is called a bronchiolar, or donut pattern. If the x-rays are ambiguous or otherwise unconvincing, the patient can be sedated and a trans tracheal wash performed. This is when saline is flushed down into the trachea and aspirated back out. The wash can then be examined under the microscope. A predominence of white blood cells called eosiniphils is diagnostic for asthma.
The typical chest x-ray of dogs and cats affected with asthma, is what is called a bronchiolar, or donut pattern. If the x-rays are ambiguous or otherwise unconvincing, the patient can be sedated and a trans tracheal wash performed. This is when saline is flushed down into the trachea and aspirated back out. The wash can then be examined under the microscope. A predominence of white blood cells called eosiniphils is diagnostic for asthma.
Treatments for asthma range from bronchodilators (medications that open the airways), antihistamines, and/or steroid If a patient is in danger, steroids are usually administered to stop the crisis. Later, once the patient has been stablized and is out of danger, milder drugs can be attempted. In mild to moderate cases, antihistamines such as chlorpheniramine or diphenhydramine can be effective. Sometimes, concurrent use of a bronchodilator such as aminophylline or theophylline will be needed. In severe cases of asthma in dogs and cats, steroids are usually necessary. In dogs, the steroid of choice to treat asthma is prednisolone, administered every other day up to as often as two times per day depending on severity. In cats the steroid of choice for asthma treatment is periodic injections of the long acting steroid Depo-Medrol. Asthma in dogs and cats can never be cured, but he disease can be successfully managed, with good quality of life attained.
Roger Welton, DVM
Founder, Web-DVM
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