Beware of Slugs and Snails and Angiostrongylus (lungworm)

snailTo a gardener, slugs and snails can be a nuisance because they eat your plants, but to dogs they can pose a serious health risk because they act as an intermediate host for one of the most serious types of internal worms.

The worm called Angiostrongylus Vasorum is sometimes referred to as lungworm or heartworm (although other types of lungworm and heartworm also exist). It affects dogs and foxes, and in the last few years it seems to have spread across most of Northern Europe including the U.K. I have seen two cases in the south-west of England in the last year. I am pleased to say that both dogs survived but they were both very ill for a time.

The life cycle of this parasite takes place partly inside the dog (the host) and partly inside the snail or slug (the intermediate host). An infected dog or fox will have adult worms in the lungs and blood vessels, which produce eggs. These worm eggs are coughed up and swallowed by the dog, and then passed out in the faeces. They are then eaten by the slug or snail, which completes the cycle of infestation when eaten by another dog.

dog_drinking_puddleIt can be easy to see, or hear, if your dog eats a snail because of the crunching sounds, but it is much harder to know if they eat slugs. Unfortunately some of the slugs are quite small and any dog which grazes on grass or drinks from puddles could be swallowing tiny slugs.

The symptoms of infection with this parasite can be quite varied. The effects on the lungs may cause coughing or breathlessness on exercise. Various bleeding disorders can be caused by the blood failing to clot, which may show as nosebleeds or bleeding in the mouth or eyes, or unexpected bleeding after surgery. Less commonly the brain, kidneys or central nervous system can be affected. All of these are serious and can be fatal.

Diagnosing the cause of the problem is by a combination of a physical examination, blood tests and faecal tests (to identify worm larvae). Other tests such as x-rays or ultrasound imaging may be necessary in cases where the symptoms are less clear cut, to distinguish this from other conditions.

The good news is that treatment is available with a number of drugs available from your vet. Some commonly prescribed worm tablets and some commonly prescribed flea treatments will kill this parasite (when used as directed by your vet, which may be more frequently than for other parasites), and this is just one reason why all dogs should follow a suitable parasite treatment regime. Dogs with more serious symptoms will require intensive care and possibly blood transfusions and other drugs.

The best advice to dog owners to avoid this problem is:

  1. Ask your vet which is the most suitable product to use for routine worm and flea treatment, and use it regularly, even if you don’t suspect that your dog has any parasites.
  2. Try to stop your dog eating slugs and snails if you can.
  3. Pick up your dog’s faeces and dispose of properly.
  4. Don’t be tempted to use slug bait, as this can be very poisonous.

Please ask at your veterinary surgery if you would like more information or advice on this very unpleasant parasite.

Jenny Sheriff BVM&S MRCVS


If you are concerned that your dog is coughing or having nosebleeds use the interactive dog symptom guide to find out what you should do.

  • Denise says:

    I have a 9 month old Working Cocker Spaniel puppy who will whenever she can bring snails in from the garden, I don’t think that she has eaten any as my husband check to see if or what she has on entering the house, has any one got got any tips as to how I could stop her doing this as she might eat one one day.from Denise.

  • Jenny says:

    It is worth trying to remove snails from the garden and especially from your pet’s mouth, but don’t forget that some of the host snails and slugs are so small that you may not see them. They can lurk in wet grass and in puddles and be swallowed without the owner noticing. So your dogs best protection is regular worming. Not all products treat this particular worm, so do seek advice from your vet and mention that your dog may eat snails. I hope your cocker puppy’s liking for snails does not cause her any problems.

  • Karan says:

    My 8 week old puppy has just eaten a snail from the garden. I’ve just seen the empty shell! He was wormed about 2 weeks ago. Can anyone advise me on what I need to do. Do i worm him again? Thanks.

  • Jill says:

    If I have already spot-on’d my dog for fleas and I think it needs a prophylactic treatment for lung worm, is there a product which can be used – preferably an oral tablet / granules?

  • jo says:

    Hi i have a 14 week old border collie i think he’s just eaten a few slugs in the garden! He was wormed and vaccinated about 3 weeks ago…. will he be ok or is it worth a trip to the vets??? Any help would be great!! Thanks!!

  • Yvonne says:

    Use corn flour put in a jar and snails slugs love it and they will die check every day .

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