October 4, 2014

Today we are referencing the coughing dog. Dogs only; cats, which are indeed a world unto themselves, need not apply. Cats want their own column. Besides, there’s lots more coughing dogs out there and plenty to discuss about each of the many possibilities behind a dog’s cough.

First, it can be surprisingly hard to determine if the complaint IS a true cough. A cough should sound like an outward sort-of-explosive breath. If smokers hadn’t been virtually banned from California, everyone would know what a true cough sounds like, but as it is there is room for doubt.  Always remember that dogs have no social compulsion to be dainty and will not try to subvert a cough into a fake sneeze or whistle. They “hack”. They may gag, but here we enter a grey area, as a dog that can’t draw breath well enough may almost vomit – but most of the time chest symptoms are different than stomach issues. I am filled with admiration for the client who can graphically imitate their pet’s cough in the clinic. On occasion I defer to the ubiquitous cell phone and request the client record a home video of the act. Is the cough productive (think wet, slimey goop coming out, maybe colored yellow or with blood) or dry?

Once we have established that a true cough is present, we can mull over the algorithm or medical pathway that leads to a diagnosis. Internal medicine is like a treasure hunt. If you enjoyed “CandyLand” as a child you will love going from clue (symptoms) to clue (diagnostic tests) as you follow the path to final diagnosis and treatment.

There is the heart cough, when leaky valves inside the heart don’t regulate blood flow properly and fluid pools in the lungs. The lungs, unsuccessfully, try to cough the excess fluid out. Or the heartworm cough. The heartworm, Dirofilaria immitis, is a mosquito transmitted worm that grows in the bloodstream and nests in the heart and lungs. Signs frequently include shortness of breath and coughing.

Bronchitis occurs in dogs, both allergic or infectious : viral, bacterial, fungal. The infamous diagnosis “Kennel Cough” springs from this group. Valley Fever falls into the fungal group. True bacterial pneumonia is relatively rare in dogs.

Foreign objects that have been aspirated or breathed into the chest, like our Valley foxtail weed awn, can set up an infection that may lead to coughing.

Chest masses and cancers, whether primary from the lung itself or metastasized, having spread to the lungs from another cancer site in the body, will take up physical space in the chest and lead to a cough.

Less malign causes are sometimes as simple as breed/body type predisposing conditions. Some breeds have a hypoplastic, very tiny trachea – it’s like trying to breathe through a straw. Others may suffer from a collapsing trachea. These conditions are common in both tiny and brachygnathic (pushed-in face) breeds – think Yorkies and Olde English Bulldogs.

I’ll tell you Jade’s story. Jade is a bouncy tricolor Rat Terrier who rarely kept more than 3 feet on the ground as she danced around. That day in February she was unusually quiet. In addition to that, her owner had heard a soft cough at home. I heard muffled lung sounds when I listened through my stethoscope. Hmmm, no leaky  heart valves and she’d had a negative heartworm test a few months back before starting on preventative medicine. We took chest x-rays, which showed a cloudy area on one side of her chest. Her bloodwork showed no sign of infection or anemia. I asked all the usual questions, but was stumped. Permission to do a chest tap to look at the fluid was granted. We drew out pure blood! Despite the negative answer to questions about mouse bait exposure, we tested Jade to see if her blood was clotting – and it wasn’t! I diagnosed a rodenticide toxicity. The missus had been doing some spring cleaning two days earlier and found an empty box of mouse bait in an unused closet. She’d tossed it without another thought.  Many mouse baits stop the body’s ability to clot blood and the animal that eats it bleeds to death, ANY animal. Bleeding may start anywhere, though it was unusual that Jade began to bleed only into her chest. The good news is that all veterinary clinics keep the antidote on hand and within hours Jade was making a full recovery. Her cough disappeared as quickly as it came.

If your dog is coughing Jade strongly recommends that you consult your veterinarian early on. We have only touched on a few of the diseases that share the symptom “coughing”. Stakes can be very high with a dog that coughs. Had her owner waited, Jade would not have been able to share her story with you today.

Christine B. McFadden, DVM
Valley Animal Hospital, Merced