Lungworms are slender, hairlike parasites about 1 centimeter long. There are several species of lungworm that affect dogs. Capillaria aerophila is acquired by ingesting eggs or a transport host, such as snails, slugs, or rodents. These parasites reside in the nasal cavity and upper air passages, producing a mild cough. Filaroides species produce a tracheal and bronchial infection that tends to be a kennel-related problem, especially in Greyhounds.
Most dogs with lungworms have mild infections and do not show clinical signs. Heavily infested dogs (usually under 2 years of age) may have a persistent dry cough, weight loss, and exercise intolerance.
Diagnosis is based on clinical signs, a chest X-ray (not always positive), and identification of the eggs or larvae in the stool or in respiratory secretions. Bronchoscopy on a dog with a Filaroides infection may reveal small nodules in the wall of the trachea. Larvae may be seen peeking out of these growths. Treatment with Panacur (fenbendazole) is often needed for extended periods of time.