By Rachele Baker, DVM – Question: Chris writes: I have a five-year-old male tabby cat who at least three times a day coughs like he wants to hack up a hairball - but rarely does (he does hack up a hairball about once a month). He also has one eye that most of the time runs with clear liquid. I assume it is excessive tearing. Can you advise what I might do to help him out?
Answer: Hi Chris. Since I am not able to perform a physical examination on your cat or any indicated diagnostics, I do not have the ability to diagnose your cat or recommend treatments. However, I can tell you some things that can cause coughing in cats. Clear discharge from the eyes is usually due to allergies. If you note eye discharge that is yellow or greenish in color, then an eye infection is more likely.
Things that can cause coughing in cats include asthma, heartworm-associated respiratory disease, fungal infections, lung parasites such as lungworms, pneumonia, or cancer in the throat or chest. Since your cat is only five years old, cancer is not high on the list of what may be causing him to cough. Since you did not describe your cat as acting sick, I think we can put pneumonia low on the list of differentials as well. So let’s discuss other potential causes for your cat’s frequent coughing.
Feline asthma: Feline asthma is caused by an allergic reaction to airborne allergens. Clinical signs of feline asthma include coughing, wheezing, and labored breathing. Airborne allergens that may cause clinical signs include cigarette smoke, fireplace smoke, and dusty cat litter. Does anyone in your household smoke? If so, you could try limiting smoking to outdoors to see if your cat’s coughing lessens or resolves. You could purchase dust-free cat litter to see if that helps. If you are sprinkling any powders on the cat litter, you should discontinue this as it may be creating more airborne allergens. If modifying your environment in these ways results in improvement in your cat’s clinical signs, then it may be that he has feline asthma. Your veterinarian can determine if your cat has asthma and may prescribe medications if indicated.
Feline Heartworm Disease and Heartworm-Associated Respiratory Disease (HARD): Cats are susceptible to infection with heartworms. Clinical signs of heartworm disease are similar to those of feline asthma and include coughing, wheezing, and labored breathing. Heartworms are transmitted by mosquitos. The prevalence of heartworm disease is higher in geographical areas with large numbers of mosquitos. Although outdoor cats are at greater risk of infection, indoor cats represent approximately twenty-five percent of confirmed heartworm cases. The map below from Antech Diagnostics (http://www.antechdiagnostics.com/Main/heartwormmap.aspx) shows the percentage of cats testing positive for exposure/infection with heartworms to date in 2013 in each state in the United States:
Diagnosing heartworm disease in cats is challenging and frequently requires a combination of tests including blood tests and chest x-rays. Your veterinarian can perform these tests.
Fungal infections: Coughing in cats can also be caused by fungal infections with such pathogens as Cryptococcus and Histoplasma. Cats can become infected by inhaling airborne fungal organisms from the environment. Some fungal pathogens such as Cryptococcus neoformans are found worldwide while others are found only in certain geographic areas.
Cryptococcosis is the most common fungal infection of cats. Cryptococcus neoformans is found primarily in bird (especially pigeon) droppings. After inhalation of the organism, cryptococcus infection is established in the lungs and then can spread to the lymph nodes, central nervous system, eyes, skin, urinary tract, thyroid glands, and abdominal organs. Clinical signs will vary depending on the organ system involved. A variety of tests may be used to diagnose fungal infections including blood tests and chest x-rays.
Lungworms: Aelurostrongylus abstrusus, the most common lungworm of cats, is found in many parts of the world including the United States, Europe, and Australia. Infection with lungworms can cause coughing, wheezing, and labored breathing. The life cycle of the lungworm includes frogs, lizards, birds, and rodents as transport hosts of encysted larvae. When one of the transport hosts is eaten by a cat, the lungworm larvae migrate from the stomach to the lungs. The lungworms live in the lungs and release larvae into the lung tissue. The cat then coughs up the larvae, swallows them, and the larvae are passed in the stool.
Routine fecal examinations used to identify parasite eggs passed in the stool are not useful for identifying parasite larvae. A special fecal test called a Baermann fecal is used to diagnose lungworm infection by identifying the lungworm larvae passed in the stool.
Your cat may have one of the things discussed above or some other problem resulting in his frequent coughing. If you have not already done so, I would recommend that you take your cat to your veterinarian for a physical examination and any indicated diagnostics so that a diagnosis can be made and any necessary treatments can be started.
I hope the information I have provided here has been helpful to you.