Lungworm in Cats

Lungworm in cats is a parasitic infection of the lower airways and lung tissue. The parasite most often discussed is Aelurostrongylus abstrusus, though other respiratory worms can affect cats too. These parasites irritate the lungs and can trigger coughing, wheezing, airway inflammation, and sometimes pneumonia. Some cats look only mildly affected, while others become seriously ill.

Outdoor cats, hunters, and cats that catch or mouth prey are at higher risk. Infection usually happens when a cat eats a rodent, bird, reptile, amphibian, or other transport host that has previously eaten an infected snail or slug. In some cases, a cat may be exposed by directly ingesting a snail or slug. Because signs overlap with asthma, bronchitis, heartworm-associated respiratory disease, and pneumonia, lungworm is easy to miss without targeted testing.

The good news is that lungworm is treatable, and many cats improve with appropriate care. The exact plan depends on how sick the cat is, how much lung inflammation is present, and whether there are complications such as secondary infection or respiratory distress. Early evaluation matters because breathing problems can worsen quickly in cats.

If your cat is coughing, breathing faster than normal, or seems less active after outdoor exposure, schedule a visit with your vet. Cats are very good at hiding illness, so even subtle respiratory signs deserve attention.

Diagnosing lungworm usually starts with a history and physical exam. Your vet will ask about outdoor access, hunting behavior, exposure to snails or slugs, and when the coughing or breathing changes began. On exam, your vet may hear abnormal lung sounds, but some cats with respiratory disease still have subtle findings.

Testing often includes chest X-rays to look for inflammation patterns in the lungs and airways. Fecal testing is important, but a standard fecal flotation may miss lungworm. A Baermann fecal test is commonly recommended because it is designed to detect larvae passed in stool. In some cats, repeated fecal samples are needed because larvae shedding can be intermittent.

Your vet may also recommend additional tests to rule out other causes of coughing or breathing trouble. Depending on the case, that can include heartworm testing, bloodwork, pulse oximetry, airway sampling, or advanced imaging. If a cat is unstable, stabilization with oxygen and minimal stress may come before a full diagnostic workup.

Because several respiratory diseases can overlap, diagnosis is often a stepwise process rather than a single test. That approach helps your vet match the level of testing to your cat’s symptoms, risk factors, and your family’s goals for care.

Cats do not usually catch lungworm directly from another cat in the way they might catch a contagious respiratory virus. For the common feline lungworm Aelurostrongylus abstrusus, the life cycle involves snails or slugs as intermediate hosts. Rodents, birds, reptiles, and amphibians can act as transport hosts after eating infected snails or slugs. A cat becomes infected when it eats one of these animals, or sometimes the snail or slug itself.

Risk is highest in cats that go outdoors, hunt, or live in areas where snails and slugs are common. Young cats may be overrepresented in some reports because they are curious hunters and may have less immunity. Multi-cat outdoor environments can also increase exposure because more cats are hunting in the same space, even though direct cat-to-cat spread is not the usual route.

Indoor-only cats generally have a much lower risk, but not zero if they have access to prey indoors or spend time on patios, enclosed yards, or gardens where snails, slugs, or small prey are present. Regional parasite patterns also matter, so your vet may think about lungworm more strongly in some climates and neighborhoods than others.

Free-roaming outdoor access raises the risk of many injuries and infections, not only lungworm. For pet parents who want outdoor enrichment, safer options include leash walks, catios, and supervised enclosed spaces.

Prevention focuses on reducing exposure and using parasite control thoughtfully. Keeping cats indoors is one of the most effective ways to lower the risk of lungworm because it reduces hunting and contact with snails, slugs, and infected prey. If your cat enjoys the outdoors, a catio or supervised enclosed area can offer enrichment with less exposure.

Year-round parasite prevention may also help, depending on the product your vet recommends. Merck lists several antiparasitic ingredients and combinations with activity against Aelurostrongylus abstrusus in cats, including moxidectin, eprinomectin in some combinations, emodepside, fenbendazole, and selamectin. Product choice matters, and labels differ by country and formulation, so use only medications prescribed or specifically recommended by your vet.

Good prey control around the home can help too. Limit access to rodents, birds, and other small animals, and reduce snail and slug attraction in gardens where possible. Routine veterinary visits and fecal testing are useful for cats with outdoor exposure, especially if they cough or have a history of parasite infection.

Prevention is not one-size-fits-all. Your vet can help build a plan based on your cat’s lifestyle, region, and tolerance for oral versus topical medication.

Many cats with lungworm recover well when the infection is recognized and treated early. Mild cases may improve over a few weeks, especially once the parasites are addressed and airway inflammation settles down. Cats with heavier parasite burdens or more severe lung damage can take longer to recover and may need repeat exams, repeat fecal testing, or follow-up chest X-rays.

Recovery is not always linear. Some cats feel worse briefly after treatment begins because dying parasites can increase inflammation in the lungs. That is one reason your vet may recommend supportive medications or closer monitoring in more symptomatic cases. If your cat’s breathing effort increases at any point, seek care right away.

Prognosis is more guarded when a cat arrives in respiratory distress, has pneumonia, or has another lung condition at the same time, such as asthma. Kittens and fragile cats may also need more intensive support. Even so, many still do well with timely treatment and careful follow-up.

At home, focus on a calm environment, easy access to food and water, and watching resting breathing rate, appetite, and energy. Ask your vet what changes should trigger an urgent recheck and when follow-up testing is needed to confirm the infection has cleared.