All About Intestinal Worms in Canines

Intestinal worms are a common problem in dogs. While intestinal worms are unlikely to cause life-threatening disease in healthy adults, they can cause serious disease in puppies and in dogs that are ill for another reason. In rare cases, worms from dogs can also infect humans. This means it is very important to give preventative worming treatment to your dog on a routine basis, and eliminate infection if a problem is found. There are many treatments available that can effectively prevent and treat worms in dogs.

What happens when a dog is infected with worms?

Worm infection does not always cause symptoms in dogs. When symptoms do develop, these arise because worms deprive your dog of nutrients and can also irritate the intestines and damage the delicate gut lining. Signs of intestinal worm infection include weight loss, poor condition, a pot-bellied appearance, diarrhoea and anaemia.

Worm infection can be very serious in puppies and it can even be fatal if the worm burden is high enough. In some cases, there can be so many worms present that the intestines can become blocked.

There are different types of intestinal worms in dogs, and the nature of the symptoms depends to some extent on the type of worms that your dog is infected with.

What types of intestinal worms can infect dogs?

Dogs can be infected with four main types of intestinal worms: roundworms, tapeworms, hookworms and whipworms. Of these, roundworms and tapeworms are the most important in the UK.

Roundworms

Roundworms look a bit like white spaghetti. They live in the dog's intestines where they can grow to about 15 cm long, and they lay a lot of eggs which are passed out in the dog's faeces. These eggs can then be either eaten directly by a dog, or be eaten by another animal such as a rodent. If the latter happens, the roundworm larvae then live in little "cysts" in the tissues of the rodent. A dog can then be infected again by eating the rodent.

In the dog's body, some worm larvae may pass into other tissues such as the liver or muscle, Larvae can also cross the placenta and infect puppies, or be passed on in the milk when puppies are suckling. This is one of the reasons why it is so important to follow a thorough worming regime for pregnant dogs and young puppies.

With roundworms, it is important to remember that the larvae can occasionally infect humans. Although this is very rare it can be serious, as the larvae can migrate into the eye and cause blindness in children. Because of this, it is important to keep your dog wormed and to make sure that your children wash their hands after they have been playing in areas where dogs may have toileted.

Tapeworms

Tapeworms are flat like ribbons, and while these can grow very long in the dog's intestines (up to 60 cm), you will generally just see little segments that break off the worm and migrate out of the dog's anus. These little segments can move by themselves, and you may see them like tiny mobile grains of rice. The segments produce eggs which are then picked up by another animal - an "intermediate host". For the most common dog tapeworm in the UK, this intermediate host is a flea. The flea larva picks up the tapeworm egg, and later on a dog can be infected by eating the flea.

Whipworms

Whipworms are a less common cause of disease for dogs in the UK. They have a simpler life cycle - the worm lives in the intestine, lays eggs which pass out in the dog's faeces, and then these eggs are eaten by a dog to cause infection.

Hookworms

Hookworms are again not so common in the UK but they can cause severe disease in puppies. These worms are short, about an inch in length, and they attach to the intestinal lining with sharp teeth and suck the dog's blood.

Their life cycle is more complicated. Firstly, adult worms in the intestine produce eggs which are passed in the dog's faeces and then develop into larvae. These larvae can then either be eaten or can invade through the dog's skin. Larvae that are eaten go straight into the intestines, whereas those that enter through the skin pass to the lungs where they are coughed up and swallowed.

When should I treat my dog for worms?

It is not always obvious when your dog has worms. While some dogs will be ill and show the symptoms described above, others may appear perfectly well. In some cases, you may see roundworms or tapeworm segments in your dog's faeces, or you might notice tapeworm segments migrating in the fur around their back end. However, other times you may see no signs at all. It is best to assume that your dog will come into contact with worms from the environment or from fleas, and treat on a routine basis.

Many different dog worming treatments are available. Some only protect against certain types of worms, so your vet will be able to advise on which treatment is best for your pet. Puppies should be wormed more frequently: the general advice is to treat every two weeks till 12 weeks of age, then every month till 6 months, then every three months after that. It is also important to check your pet regularly for fleas and treat as necessary, as this will break the lifecycle for the most common dog tapeworm.

It is always sensible to take other basic hygiene measures to reduce the likelihood of worm infection, such as cleaning up dog faeces promptly and making sure that your children wash their hands after playing anywhere where a dog may have toileted.

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