The cat lungworm Aelurostrongylus abstrusus is the most common species in domestic cats. Adult worms live deep in the lung tissue, where the female lays eggs that hatch into larvae. The cat coughs these up, swallows them, and passes them in its faeces — continuing the cycle.
How cats catch it
Cats don’t usually eat slugs and snails directly. Instead they become infected by hunting and eating “paratenic” hosts — birds, rodents, frogs and lizards that have themselves eaten infected molluscs. This is why free-roaming hunters and farm cats are at far greater risk than indoor-only cats.
Signs in cats
Many cats carry a light infection with few signs. When symptoms do appear, they include a chronic cough, wheezing, rapid or open-mouthed breathing, and reduced energy. Kittens, older cats and those with other illnesses tend to be affected more severely.
Cats hide illness well
A cat that is breathing faster than usual at rest, or that suddenly avoids exertion, deserves a vet check. Respiratory signs in cats should never be left to “see if it passes.”
Treatment in cats
Feline lungworm responds to several anthelmintics. Fenbendazole is commonly given over a course of days, and certain spot-on products containing macrocyclic-lactone drugs are also used. Because the worms sit in lung tissue, a single dose is often not enough — your vet will advise on the full course and whether a follow-up faecal test is needed.
Use the calculator for a fenbendazole starting estimate based on your cat’s weight, then confirm with your veterinarian.
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