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Worming your dog

What worms can dogs get?

Dogs can get three different types of worms: roundworms, tapeworms and lungworms.


Roundworms are spaghetti like in appearance, usually 8-15cm long, and live in the small intestine. They are not normally seen in the stools. The adult worms shed thousands of microscopic eggs each day which pass out in the dogs faeces and contaminate the environment. Puppies are usually infected from their mother via the placenta and through the milk.  Dogs are also infected by unwittingly eating the roundworm eggs, or by eating an “intermediate host” such as a mouse.


Tapeworms are long, flat and segmented. Infected dogs shed tapeworm segments containing microscopic eggs in their faeces. The most common dog tapeworm segments resemble grains of rice and can sometimes be seen moving around in the hair around your dog’s anal area. This type of tapeworm is often caught via fleas –  flea larvae eat the tapeworm eggs in an infected dog’s faeces – when other dogs pick up the fleas and eat them during grooming they also become infected. Another tapeworm species is transmitted via rodents and is less common.


Until relatively recently few dogs were diagnosed with lungworm in the UK. However, a new and serious threat to dogs has emerged with the establishment of a lungworm called Angiostrongylus vasorum. Adult lungworms live in the pulmonary arteries and right ventricle of the heart. Affected dogs show a wide range of symptoms – some severe, including coughing, fits, bleeding problems, and lethargy. The lungworm parasite is carried by slugs and snails which act as an intermediate host. Dogs sometimes eat slugs and snails, but even snail slime trails left on grass and toys can be infectious.

What are the signs of having worms?

Most dogs show no obvious signs when they first catch worms. Heavy roundworm and tapeworm infections can partially block the intestines and cause weight loss, vomiting, anaemia and failure to thrive. Puppies often appear bloated and may have diarrhoea and/or blood in the faeces. Lungworm can cause coughing, blood clotting problems and even seizures.

Human health implications

Humans can be infected with roundworm (Toxocara canis) and tapeworm (Dipylidium caninum). Toxocara is potentially dangerous in children, where ingestion of the worm eggs may result in migration of the larvae through the body. If they go to the back of the eye they can cause blindness. Although this is rare, we advise you to be particularly vigilant about worming your dog if you have young children. Even if you don’t have children your dog may still go where children play.

How frequently should I worm my dog, and what with?

We advise breeders to treat puppies for roundworm at two and five weeks of age, and then again before the puppy goes to a new home. It is a good idea to ask the breeder if this has been done.

Puppies under 12 weeks of age should be treated for roundworms every 2-3 weeks.

The frequency and type of medication used for older puppies and dogs is determined by the lungworm risk and the environment the dog lives in. The range of products available and the different combinations of flea, worm and mange protection can be bewildering. Please discuss your requirements with us so that we can advise you on the best worm and flea treatment for your pet.

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