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Lungworm warning as summer arrives

Slugs and snails the main culprits

The recent warm and damp weather has as usual encouraged the slugs and snails to come out of hiding in some force. Dog owners in particular are becoming more aware of the worm Angiostrongylus vasorum - commonly referred to as lung or heart worm - as are vets across the UK.

Until recently it was thought that this worm was only to be found in the south of the UK but there have been reports right across the UK as far north as Scotland. The geographical distribution of the parasite has expanded northwards, but it is very patchy.

Most vets will advise owners to worm their dogs with Milbemax or Advocate for this parasite. Dogs can become infected with this parasite by eating or accidently ingesting slugs and snails. As dogs will scavenge, food or faeces or through grass-chewing, they can accidently eat a small snail or slug even though they are not known to be slug and snail eaters, any dog can become infected.
Dog owners should make sure that at the end of the day all their dogs toys, chews and bones should not be left in the garden or anywhere such as a garden shed where a slug or snail will have access to them and could hide eventually to be inadvertently be eaten by their dogs.

Eric Morgan of Bristol University is currently researching the spread of this parasite, he told us, “It is a real shame, though, to see dogs going down with it even though their owners believe they have taken care of worming, I am not aware of any adverse reactions to treatment with Milbemax or Advocate. There are some old reports of anaphylactic shock following treatment of heavy burdens of worms with levamisole, but this is no longer used and most vets would take precautions against this anyway during treatment. The fear of toxicity following long term preventative use of macrocyclic lactones also has no basis in the literature, but is a personal choice I guess. We know very little about whether less frequent worming (i.e. longer than the pre-patent period of the parasite) has any protective effect”.

Some owners concerned that these worming medications are not suitable for their breeds are working with their vets and taking faecal samples on a daily basis to try to detect evidence of slug and snail eating. This is then followed by a worming programme under veterinary supervision.


Bleeding disorders are a common symptom of this worm, particularly internal bleeding, which is a consequence of infection, and an affected dog is often (though not always) presented in an advanced state which makes it hard to reverse the damage. The most commonly seen symptoms of lungworm infection are reluctance to exercise, coughing, (which may sound like the dry cough of kennel cough), depression, weight loss, fits, vomiting, weakness, paralysis/inability to walk and excessive bleeding from minor wounds.

It has been claimed that dogs can pick up the worm from simply licking the slime trails left by the slugs and snails. However after testing numerous slime trials no evidence of worm larvae have been found. More research into this parasite and its intermediate hosts is needed.

We asked Eric Morgan for advice to reduce the risk our dogs becoming infected, “Laying down slug pellets is obviously a really bad idea. Depopulation of slugs using beer traps or picking up in torchlight is likely to work only very rarely, in small and well enclosed gardens. Avoiding leaving dogs in the garden or off-lead outside the home during periods of high slug activity (dawn and dusk in warm and humid weather) should reduce infection risk, though there is no proof of this. We are conducting quite a lot of research this year into infection in the intermediate hosts using a new PCR test, and are developing improved diagnostic tests for dogs, which we will employ in risk-factor studies. So we are building on the admittedly weak evidence base. It has been hard to raise funds for this in the past as awareness was low, hence the poor current state of knowledge”.

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