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Lungworms in dogs (Angiostrongylus)

Referring to Angiostrongylus vasorum as a lungworm is quite misleading. Although the early stages of the parasite do affect the lungs and severely infected dogs may show signs of coughing, other signs are far more common. These lungworms (Angiostrongylus vasorum) are also known as the French heartworm. This is a parasite where the adult worm infects dogs but the young stages are carried by slugs and snails. The parasite itself may not cause the dog any problems unless present in very large numbers. However, in order to survive in the blood vessels the parasite releases substances which affect the clotting of  the host's blood. Thus infected dogs are more prone to bleeding than normal dogs. This bleeding can pose a life-threatening risk to an affected pet. Thus this parasite is can be more dangerous to a  dog than the more common worms that live in the intestine and it is very important to take precautions to prevent infection. This disease used to be confined to dogs living in the South of the country (especially the South East, South West and South Wales). However, in the last ten years the disease has become much more common and has been seen in dogs as far North as Scotland. All dogs in the UK should now be considered potentially at risk.

Your questions answered

How could my dog get infected?

The adult worms spend most of their lives in the blood vessels close to the heart. However, when the eggs laid by the adults hatch, the immature worms (larvae) force their way through the walls of the blood vessels and into the lungs. The dog then coughs up the larvae and swallows them. The larvae pass into the faeces which is in turn eaten by slugs and snails (which love dog poo!). The larvae develop in their new host until this is eaten by a dog. Slugs and snails often crawl into dog's food bowls or onto toys if these are left outside. Dogs also eat these garden pests when drinking from outdoor water sources and eating grass. Once back in the dog the young worms make their way back through the dog's body to the blood vessels.

How do I know if my dog is infected?

Many infected dogs show no signs of illness. Dogs that are unwell show a wide range of symptoms: breathing problems, coughing, bleeding excessively from cuts or bleeding internally with no signs of trauma, anaemia and loss of condition. Other animals may show neurological changes including seizures. If your dog is unwell in any way make an appointment to see your vet.

How would my vet know what is wrong with my dog?

Not all dogs with lungworm show breathing-associated signs. The adult worms in the blood vessels and heart can cause heart failure but also produce a substance to stop the blood clotting. This can cause your dog to bleed, with or without an injury. The bleeding can take place inside the body and may affect the brain or eyes resulting in seizures or blindness.

It is unlikely that your vet will know straight away what is wrong with your dog and they will need to do a number of tests in most cases to make the diagnosis. If you live in an area where lungworm is common your vet may be more familiar with the disease and may be suspicious of the signs at an earlier stage. If there is a suspicion that your dog is infected your vet can do a test for lungworms.

If my dog is infected can it pass disease to me or my other pets?

The infection can't pass direct from to dog without first passing through a slug or snail. However, if you have several dogs living in the same household and one is found to be infected it is likely that the others will also be at high risk of infection. The common lungworm of dogs (Angiostrongylus vasorum) does not affect cats or people.

What is the treatment for lungworm?

The aims of treatment are to eliminate the lungworm infection and also to manage the clinical signs. There are a number of drugs that can be used to eliminate the worms but infected dogs should be monitored carefully when receiving treatment as the sudden killing of the worms could result in a severe allergic reaction.

If your dog has severe signs (particularly affecting the brain or signs of heart failure) your vet will want to keep your pet in the hospital for specialised care.

Will my dog get better?

Most dogs go on to make a full recovery with appropriate treatment. However, infection can prove fatal for some dogs despite intensive treatment.

How can I protect my dog against lungworm?

Most dogs are infected by contact with slugs or snails (and usually from eating these) - so if you can reduce your dog's exposure to these that will reduce the risk.

Regular treatment of your dog with a product that can kill the worms can help to protect them against infection. The standard worming treatment that you give your pet every 3 months or so may not protect them from lungworm infections. You will need to get additional treatment from your vet and this may be given in the form of a monthly spot-on (at the back of the neck) which will protect against lungworms and treats your dog for other common parasites such as fleas, worms, and mites. Contact your own vet for further advice on the risks to your dog and how to manage them.

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