Lungworm infection in cats

© Norsworthy, G et al (2003) The Feline Patient. Lippincott Williams & Wilkins, Baltimore MD.

Lungworms are helminths that live in the alveoli, bronchioles, bronchi and trachea of cats. Many affected cats are asymptomatic, whereas may others develop a dry cough. This is one of the few causes of chronic coughing of cats and should be considered if the geographic area is endemic for feline lungworms. There are two lungworms of the cat: Capillaria aerophila and Aelurostrongylus abstrusus. Capillaria has a direct life cycle and may be transmitted through earthworms and rodents. Cats are infected by ingestion of the embryonated ova or one of the paratenic hosts (rodents, earthworms). Adult worms live within the epithelium of the trachea, bronchi and bronchioles and produce ova about 40 days after infection. The ova are coughed up, swallowed and passed in the faeces. They become embryonated in 1 to 2 months but can survive in the environment for more than a year. The cat becomes infected with Aelurostrongylus when it eats the intermediate hosts (snails or slugs) or paratenic hosts (birds, rodents, amphibians, or reptiles). The adults live in the alveoli and are capable of producing ova about 25 days after ingestion. The ova hatch and become larva, which migrate up the bronchi and trachea into the pharynx. They are swallowed and passed in the faeces, where they can survive for several months. An intense immune response causing focal interstitial pneumonia is responsible for elimination of the worms in most cats.

Larval stage of A. abstrusus	Alveoli of cat filled with embryonated eggs and larvae of Aelurostrongylus abstrusus surrounded by mononuclear infiltrate.
Intra-alveolar larvae of the parasite Aelurostrongylus abstrusus.	Dead parasite Aelurostrongylus abstrusus in the bronchioles.
Dead parasite Aelurostrongylus abstrusus in the bronchioles.	Dystrophic calcification and intercellular bronchiolar infiltrate in a cat infested by parasite Aelurostrongylus abstrusus

A Baermann faecal floatation test can be used to test for lungworm larvae in the faeces. Radiography may reveal peribronchial infiltrates, bronchial thickening, or a diffuse interstitial pattern.

Treatment

Fenbendazole (Panacur) is a recommended therapy, given at 50-100 mg/kg PO q 24hrs for 7-14 days for capillariasis. For Aelurostrongylus, Panacur is given for 4 days, then given another for another 4 days about 10 days later.

Ivermectin, as an alternative therapy can be given at 400 μg/kg SQ or PO, then repeated in 2 weeks.