Downeast Dog News
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How to recognize lungworm in your dog

May 01, 2017

Q. My dog is coughing. He has had tons of tests. Antibiotics and steroids have not helped. What else could be going on?

A. Coughing in dogs can be caused by viruses if your dog goes to kennels or other areas that have a lot of dogs, bacterial infections, heart conditions, and hormonal imbalances, and finally parasites. Roundworms have a stage where the larvae moves into the lungs, gets coughed up and swallowed, and then finishes growing into an adult.

There is another cause of coughing which is often overlooked. This is a parasite called lungworm. The common lungworm here in North America is the fox lungworm.

Infected cats will cough up the larvae, an adolescent stage, and swallow it. The larvae will pass in the poop which will infect snails and slugs. Dogs and foxes, the final hosts, will ingest the snails and slugs. The larvae are released in the gut and migrate into the airway passages of the lungs, bronchi and bronchioles, to grow into adults.

The most likely time of infection is during wet and warm seasons, spring and fall. This is the active slug and snail time. The life span of this worm is 8 to 10 months, so infection can be detected in a dog anytime during the year.

A dog infected with a few worms may not show any signs of a cough and the infection can spontaneously go away. The problem is with a heavier burden of worms. The symptom commonly seen is a chronic cough, but sneezing, nasal discharge, and retching can occur. These dogs develop inflammation in the airways, trachea, and bronchi called tracheitis and bronchitis. If severe, the dog can stop eating and become weak. With severe infection, a dog can develop bronchial pneumonia. You can see how this worm infection can be confused with allergic bronchitis.

To diagnosis this problem, your veterinarian will check a poop sample. Using normal techniques, this parasite can be missed. Sometimes multiple samples over a period of a couple of weeks is needed because the larvae is shed sporadically. There is a special test called Baermann technique that is more successful in finding the worm. Another test to diagnose lungworm is a technique called tracheal lavage.

On Prince Edward Island in Nova Scotia, researchers found this parasite in about a third of shelter dogs.

Lungworm is easily treated with a common wormer from your veterinarian.

If you find your dog having a cough that he can’t shake, his teeth are clean, heart is fine, antibiotics and steroids didn’t help, and you and your veterinarian are scratching your heads, you may want to check his poop.