Aelurostrongylus abstrusus, the cat lungworm is a parasitic roundworm that has cats as final hosts. It is found worldwide, including Europe, the US and Australia, with a variable incidence depending on the particular region. Studies in Germany and Denmark showed that about 6% of the cats were infected.
Aelurostrongylus abstrusus does not infect livestock (cattle, sheep, pigs, etc.) or dogs.
The disease caused by Aelurostrongylus abstrusus is called aelurostrongylosis.
Are cats infected with Aelurostrongylus abstrusus contagious for humans?
- NO. The reason is that this worm is not a human parasite.
Final location of Aelurostrongylus abstrusus
Predilection site of adult Aelurostrongylus abstrusus are the terminal bronchioles and the alveolar ducts inside the lungs.
Anatomy of Aelurostrongylus abstrusus
Adult Aelurostrongylus abstrusus are rather small worms, usually not more than 10 mm long and 1 mm thick, with a dark brownish color. Males are shorter than females. As other roundworms, the body of Aelurostrongylus abstrusus is covered with a cuticle, which is flexible but rather tough. The worms have no external signs of segmentation. They have a tubular digestive system with two openings, the mouth and the anus. They also have a nervous system but no excretory organs and no circulatory system, i.e. neither a heart nor blood vessels. The female ovaries are large and the uteri open near the posterior end. Males have chitinous spicules for attaching to the female during copulation.
The eggs are spherical to oval, and contain a single cell. The larvae hatch already in the alveoli and consequently the feces of the host do not contain eggs but young larvae.
Aelurostrongylus abstrusus has an indirect life cycle, with cats as final hosts, and snails or slugs as intermediate hosts. However, other small vertebrates (e.g. rodents, birds, frogs, lizards, etc.) can act as transport (paratenic) hosts. In these transport hosts the worms do not complete development to adults, but are infective for cats if they east these intermediate hosts.
Adult female worms lay eggs in the lungs of infected cats. Young larvae hatch out of the eggs already in the airways and start migrating towards the mouth. Coughing, sneezing or the mucus brings them to the mouth, where they are swallowed. Subsequently these larvae are shed with the host's feces and remain infective for up to 6 months under suitable weather conditions. These larvae are capable of actively penetrating into snails or slugs. Inside these intermediate hosts they develop to L3 larvae within about 3 weeks. When transport hosts (rodents, frogs, lizards, birds) eat these infected snails or slugs, the larvae migrate into the body tissues without completing development to adult worms. When a cat eats such transport hosts, the infective larvae are released in the cat's stomach, penetrate the gut's wall and migrate towards the lungs along the blood vessels. They reach the lungs about 1 day after infection. In the lungs they complete development to adult worms and reproduce.
The time between infection and first larvae found in the feces (prepatent period) is about 4 weeks.
Harm caused by Aelurostrongylus abstrusus infections, symptoms and diagnosis
Infections with a few worms are usually benign, cause no clinical signs and recede spontaneously. Massive infections cause no specific symptoms such as chronic cough, sneezing, nasal and eye discharge, weakness, loss of appetite, etc. Very severe cases can cause bronchial pneumonia. Fatalities are very seldom, only in cases of massive sudden infection of the lungs with larvae.
Diagnosis is confirmed through detection of larvae (about 400 micrometers long; Baermann method) in the feces. However, shedding of larvae is intermittent, i.e. false negatives are possible. Examination of bronchial liquid is more reliable. Radiography of the lungs may reveal the presence of worms or other related tissue anomalies.
Prevention and control of Aelurostrongylus abstrusus infections
In endemic regions cats should be prevented from eating potential transport hosts (frogs, lizards, rodents, birds) but this may be rather difficult to achieve in rural regions where the cats are often outdoors.
Some anthelmintic active ingredients (e.g. fenbendazole, emodepside, ivermectin ) are known to be effective against Aelurostrongylus infections. However, since most commercial dewormers are not approved for use against this worm, the veterinary doctor has to determine a special treatment regime.
There are so far no true vaccines against Aelurostrongylus worms. To learn more about vaccines against parasites of livestock and pets click here.
Biological control of Aelurostrongylus worms (i.e. using its natural enemies) is so far not feasible.
You may be interested in an article in this site on medicinal plants against external and internal parasites.
Resistance of Aelurostrongylus worms to anthelmintics
So far there are no reports on resistance of Aelurostrongylus to anthelmintics.
This means that if an anthelmintic fails to achieve the expected efficacy, chance is very high that either the product was unsuited for the control of Aelurostrongylus, or it was used incorrectly.
Ask your veterinary doctor! If available, follow more specific national or regional recommendations for Aelurostrongylus control.