What’s Causing My Cat’s Persistent Cough?


My 4-year-old calico started with some bad coughing about three weeks ago. She has seen the vet and we have had her on azithromycin, then Baytril. She had X-rays and the vet said her lungs and trachea were clear and perfect! They ruled out asthma, but I am not so sure.

We changed the kitty litter because maybe the cedar was getting in her lungs and causing allergies. I gave her some Benadryl (per vet) and that helped for a while, but the coughing started again. By the way, she has had an upper respiratory infection since we got her (she was a stray). Any thoughts or suggestions?

Brooklyn, NY

Like you, I am not convinced that asthma is ruled out. More on that in a moment.

In cats, the most common cause of coughing is irritation of the bronchi (air passages) in the lungs. This inflammation is called bronchitis and comes in two main forms: infectious (caused by bacteria) and allergic (also known as asthma).

I would have been highly suspicious of an infectious bronchitis as the cause of your cat’s coughing since she has a history of upper respiratory infection. Upper respiratory infections, which affect the nose, sinuses, and eyes, can sometimes spread into the throat or the lower respiratory tract to cause bronchitis or even pneumonia, which can cause coughing.

The antibiotic trial was a wise first step. You describe two of them: one with azithromycin and one with Baytril. Your cat’s failure to respond, even slightly, to these drugs makes an infectious process much less likely.

So, working through the process of elimination, we are left with one other common cause of coughing (asthma) as well as a few rare causes: lungworm, which aren’t common in my experience; cancer, which is very rare in four-year-old cats, and which often shows up in X-rays when it is severe enough to cause coughing; foreign body in the trachea or lungs; and a couple of other also-rans.

I strongly suspect that asthma is causing your cat’s symptoms. It is by far the most common cause of situations such as yours.

And what about those clean X-rays? Many mild cases of asthma are not visible on X-rays. The inflammation of the airways has to be quite severe for it to cause the classical radiographic appearance of asthma. Milder inflammation can lead to symptoms with normal X-rays.

Although feline asthma is also known as allergic bronchitis, it does not respond well to antihistamines that are used to treat allergies in humans. The failure of your cat to respond to Benadryl is thus not surprising.

The treatment for asthma involves use of bronchodilators, inhaled steroids, or oral steroids. You may want to consider treatment (although be aware that oral steroids in particular might exacerbate the upper respiratory infection). Or you could ask your vet about a tracheal wash with cytological analysis.

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