What are lungworms?
Lungworms are slim, hair-like nematodes that live in the lungs of mammals. The two most common species to infect cats are Aelurostrongylus abstrusus (feline lungworm) and Capillaria aerophila (Eucoleus aerophilus) (feline and canine bronchial capillarid).
Lungworm was once thought to be a rare infection in cats, but an Australian study found 16% of cats at a Melbourne shelter were infected with lungworm . Cats of any age, sex or breed can become infected; however, it is most common among cats allowed outside who hunt.
Distribution of lungworm
The geographical distribution of Aelurostrongylus abstrusus and Capillaria aerophila is worldwide.
- Capillaria aerophila – This parasite has a direct life cycle which means it does not need an intermediate host to complete its life cycle. Infected rodents can transmit infection and earthworms may act as an intermediate host by when they ingest eggs in the environment. Cats become infected by ingestion of food (including prey) or water infected with larvae.
- Aelurostrongylus abstrusus – Ingestion of intermediate hosts such as a snail or slug, or more commonly by consuming animals who have been feeding on snails and slugs such as birds, rodents, and lizards.
After ingestion of both species, the larvae pass into the intestine. From there they penetrate through the intestinal wall and migrate to the lungs via the blood where they remain in the terminal respiratory bronchioles and alveolar ducts of the lungs and mature into adult lungworms reaching a length of length 5–12 mm.
The female lungworm worm lays eggs that hatch into microscopic larvae, they then travel up the trachea and are swallowed into the stomach before being passed into the environment via the cat’s feces. Larvae appear in the feces around 40 days post-infection.
Cats are commonly asymptomatic to lungworm; clinical signs depend on age, health status and immune response and can range from mild and self-limiting to severe and life-threatening.
- Chronic dry cough
- Nasal discharge
- Shortness of breath (dyspnea), especially upon exertion
- Open-mouthed breathing
- Lethargy and exercise intolerance
- Loss of appetite (anorexia)
Complications may include interstitial emphysema (a collection of air outside of the normal air space of the pulmonary alveoli), pulmonary edema (fluid in the air sacs of the lungs), pneumothorax (air in the pleural cavity), secondary bacterial pneumonia and increased anesthetic risk. Lungworm can be particularly serious in kittens and immunocompromised cats.
The veterinarian will perform a physical examination of your cat and obtain a history from you.
A diagnostic workup is necessary to rule out other respiratory diseases with similar clinical signs.
- Tracheal wash: A small plastic tube (catheter) is passed into the airways, a small amount of fluid can be passed (washed) into and out of the lungs to look for larvae.
- Fecal examination (Baermann technique): A fecal sample is suspended in water in the bowl of the glass for several hours, which allows first-stage lungworm larvae to migrate out of the feces and into the water. This may require several tests as larvae are not always present in the feces.
- Radiographs: May reveal lung patterns, bronchial wall thickening and increased interstitial opacity.
- An enzyme-linked immunosorbent assay (ELISA): For the detection of antibodies against A. abstrusus.
Several worming medications can be prescribed to treat lungworm, however, treatment can be challenging, and it may be necessary to continue the anti-worming medication for up to 8 weeks. In some cases, more than one anti-parasitic medication will be necessary.
In addition to anti-parasite treatment, the veterinarian may prescribe corticosteroids to reduce inflammation.
Can humans catch lungworm from infected cats?
Humans can catch lungworms, but you can’t catch lungworm from an infected cat. Wash fruit and vegetables thoroughly before consumption.
- The best way to prevent lungworm in cats indoors so they can not hunt.
- Make sure cats who do have access to the outdoors are up to date on their worming medication.
- Speak to your veterinarian for advice on the best lungworm preventative treatment for your cat.
If you notice any symptoms associated with lungworm, see your veterinarian.
 JAVMA, Vol 235, No. 1, July 1, 2009, p48