Lung Worms in Cats
Are extremely difficult to identify and diagnose but are quite easy to treat

Lung worms in cats used to be very rare, but this condition is starting to grow in alarming rates in both cats and dogs.

If your cat suddenly starts to cough or is losing weight for no apparent reason, or if they are showing any unusual signs of respiratory stress, there is a very good chance that they have become infested with lung worms.

Lung worms are extremely difficult to diagnose, but are relatively easy to treat once they have been diagnosed.

Originally discovered in France, they are also called French heart worms, and are a growing concern in the UK and several European countries and they are now a growing concern in the United States as well.


Lung worms in cats are a form of a parasite, also referred to as a worm, and they come in three distinctive forms: Aelurostrongylus abstrusus, Paragonimus kellicotti and Capillaria aerophilia.

The Aelurostrongylus abstrusus form of this parasite will affect your cat during its life cycle in its intermediate host, which are snails as well as slugs.

However, they also have what is referred to as a transport host.

This means they are transmitted or carried and this include birds, small mammals, as well as some reptiles.

This form of parasite is found virtually worldwide.

The second form of Lung worms in cats, Paragonimus kellicotti, does not affect cats as it primary victim is dogs and it is transmitted by crayfish and snails.

Deep blue eyes in catsLung worms in cats can affect all breeds regardless of where they live


The major transfer host is a raccoon and it is found almost exclusively in the United States.

The third form, Capillaria aerophilia, have a direct life cycle, meaning that it can infect one host directly and does not need an intermediate host.

They are also found primarily in the United States.

Lung worms life cycle is the same as any other type of a parasite, as they first infect the intermediate host.

From here they move from the intermediate host to the main host, in this case your cat, where they migrate to various organs within your cat.

Once they have migrated, they begin to mature. Once matured, they will than begin to lay their eggs.

These eggs than migrate into your cat lungs via their bloodstream.

Once in the lungs, they develop tissue like nodules that consist of cellular infiltrate that are filled with larvae and eggs.

They will than hatch and move into your cats alveolus, which is a microscopic air sac in the lungs.

This small air sac is found at the end of the very fine divisions of the bronchioles through which gaseous exchanges take place.

From there they are transported by this gas and air into your cat’s larynx where they are swallowed.

This cycle will than start repeat, as larvae are transmitted back into the soil from their feces where it waits for another intermediate host.

Your cat usually becomes infected by eating infected snail or slugs, but they can also be infected by eating the remains of a transmitting host, in most cases a bird or a rodent.


Lung worms in cats have several symptoms, but it may be helpful to understand that this is not a condition that applies only to outside cats that roam.

Snails and slugs are commonly found around lakes and any type of water, but they are also commonly found in flower beds and grassy areas.

If your cat never goes outside, they have very little chance of being infected.

However, if they go out only briefly, they still are at risk and this is one of the major reasons why lung worms in cats is growing at the rapid rate.

In fact most owners are not concerned by their cat being in their immediate yard or surroundings.

The first set of symptoms of Lung worms in cats that you will see will be a slow weight loss as they are losing their appetite as the eggs hatch and migrate.

Shortly after they start to lose weight, the infection in the lungs will cause a difficulty in breathing that will become very noticeable.

But the most chilling symptom of Lung worms in cats will be a very sudden and then chronic coughing.

This is the result of lung worms migrating up through their larynx.

Coughing in cats should be the most chilling symptom that you ever hear, as it is never normal.

If your cat starts to cough, there is always an underlying reason and that reason will never be a good one.


Diagnosis of this infection is very difficult simply because it emulates so many other possible conditions such as bronchitis, asthma, heart disease, and pneumonia.

It is often confused as well with heart worm disease, which is the kiss of death in most cases, but this infection is not anywhere near that serious.

The treatments will consist of anti-parasite drugs which are common in treating any worm infection, as well as anti-inflammatory drugs if the reaction has been severe.

The treatment for the Aelurostrongylus abstrusus form of lung worms, which is the most common, will consist of Fenbendazole for up to ten days as well as Ivermectin, usually for three to four days.

The capillaria aerophilia form will consist of treatments again with Fenbendazole for the same ten days.

However, it must also be combined with Albendazole for 10 to 20 days, as well as Ivermectin, but usually will only consist of one or two doses.


Lung worms in cats will in most every case have a very successful outcome.

However if it has been overlooked or neglected for several months, in which case it can cause a permanent scarring of your cats lung tissue.

If this has occurred, your cat may cough intermediately for the rest of their life.

The best method of prevention is to minimize your cat’s exposure to both snails and slugs.

This infection is one of the reasons why indoor cats live up to fifteen years or longer in some cases, while an outdoor cat has a life span of about five years.

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