Lungworm in Dogs in the UK: How Dogs Catch It, Signs and Prevention

Lungworm is a parasite that dogs catch by eating infected slugs and snails, often by accident while eating grass, picking things up on walks or sniffing about in the garden. It can make dogs seriously unwell, but prescription prevention from your vet and a few simple habits lower the risk.

Lungworm is a risk to dogs across much of the UK. It has spread to more areas over the past decade and is now found as far north as Scotland. The signs can be varied and may look like other illnesses, so it is not something to try to diagnose at home. If your dog seems unwell, especially if their breathing has changed or they are bleeding for no clear reason, contact a vet.

What lungworm is

The lungworm that causes serious illness in UK dogs is called Angiostrongylus vasorum. Adult worms live in the heart and the blood vessels that supply the lungs, so despite the name, its effects are not limited to the lungs. Infection can cause breathing problems and bleeding disorders, and severe cases can lead to seizures or death.

Foxes are an important wild host in the UK. Infected foxes and dogs pass lungworm larvae in their poo, and slugs and snails pick up the larvae when they feed on it. A dog may then become infected by swallowing an infected slug or snail. Frogs can also carry the larvae after eating infected slugs or snails, so they are another possible source of infection.

Your dog does not need to miss out on walks or time in the garden, but keep an eye on what they scavenge and make lungworm part of their routine parasite control.

How dogs catch lungworm

Most dogs catch lungworm by eating infected slugs or snails. Sometimes this is obvious, such as when a dog tries to eat one in the garden. Often it is accidental. A small slug or snail can be on grass, and dogs may swallow one while eating grass or drinking outside.

Dogs that scavenge or chew things they find outdoors may have more chances to swallow a slug or snail without anyone noticing. Advice from the Royal Veterinary College (RVC) also warns against leaving toys and sticks outside for dogs to chew, as they can attract small snails which a dog may then eat.

Supervise your dog where you can and calmly interrupt scavenging. Do not let them eat slugs, snails or frogs. Bringing toys, sticks and chews indoors after use also removes places where small snails may gather. These habits lower the chance of exposure, although they cannot remove it completely.

Signs that need veterinary advice

Lungworm signs are often vague and can differ from one dog to another. Coughing or weight loss does not automatically mean lungworm, but it does need checking if it is new or ongoing. A vet can assess your dog and consider other possible causes too.

Possible signs include:

• coughing

• fast, heavy or noisy breathing

• tiring more easily than usual

• weight loss or a reduced appetite

• unexplained bruising or bleeding

• collapse or shock

• seizures

• sudden blindness.

Contact your vet straight away if you notice possible signs of lungworm. Breathing difficulties, collapse, a seizure, sudden blindness or significant bleeding need urgent veterinary attention. Call an emergency veterinary service if your usual practice is closed.

Some dogs have signs that seem less dramatic at first, such as a cough, reduced appetite or a reluctance to exercise. It is still best to make an appointment promptly rather than waiting for them to pass. Dogs that are diagnosed and treated before severe signs develop generally have a better outlook.

How lungworm is checked and treated

There is no reliable home test for lungworm. Your vet will ask about your dog’s health, lifestyle and parasite prevention, then decide which tests may help. A poo (faecal) test can look for larvae, but larvae are not passed all the time, so samples from several days may be needed. A blood test for lungworm antigen can also support diagnosis.

Dogs with breathing problems or bleeding may also need blood clotting tests or chest X-rays to show how badly they are affected.

Do not give a worming product because you suspect lungworm unless your veterinary practice has told you to do so. Treatment depends on how ill a dog is and the signs they have. A seriously affected dog may need hospital care, including oxygen, fluids or other medicines, as well as treatment for the parasite.

Preventing lungworm in dogs

Prevention starts with reducing the chance that your dog will swallow slugs, snails or frogs. It also means asking your vet whether their parasite plan should include lungworm protection. Many wormers, including those sold in pet shops and supermarkets, do not protect against lungworm. Lungworm prevention is only available on prescription from a vet.

There is no one plan that suits every dog. Risk can be affected by where your dog lives, how much time they spend outdoors and whether they are likely to scavenge. The British Veterinary Association supports a targeted, risk-based approach to parasite treatments instead of blanket treatment. This matters because some parasiticide products can reach the environment and harm non-target wildlife. For lungworm, ESCCAP UK & Ireland, which publishes parasite guidance for vets, advises monthly protection for dogs at risk, so ask your vet whether your dog falls into that group.

Your veterinary practice can advise whether lungworm protection is suitable for your dog, which prescription product to use and how it should be given. Follow the product label and your vet’s advice. If your dog’s routine changes, such as spending more time in the garden or starting to scavenge on walks, mention it at their next health check.

On walks, keeping your dog on a lead in places where they are likely to scavenge can help you step in before they eat something unsuitable.

If your dog eats a slug or snail

If you see your dog eat a slug or snail, make a note of the date and contact your veterinary practice for advice, particularly if your dog is not on a lungworm prevention plan or develops signs of illness.

Do not try to make your dog sick or use home remedies. Your vet can advise whether your dog needs an examination and whether their parasite plan needs reviewing. If they develop coughing, breathing changes, bruising, bleeding, collapse, seizures or sudden blindness, seek veterinary help straight away.

Signs of lungworm can take several weeks to appear after infection, so keep watching for them even if your dog seems well at first.