There are 2 main types of worms in dogs – roundworms or tapeworms.

ROUNDWORMS
Toxocara canis is the name of the common roundworm in dogs. The worm is round in cross section like an earthworm. The adult worm looks like a piece of plastic covered wire, between 5 and 15cm long, pale beige/grey in colour, curved or coiled into a spring shape. The worms can be seen when the dog vomits, although they are rarely the cause of the sickness. Roundworms do little harm to adult dogs, but puppies can have problems if they have large numbers of worms.

LIFE CYCLE: The adult worms live in the dog’s intestines, where they mate and lay eggs invisible to the naked eye. These are passed in the faeces and develop in a warm, moist environment, in about 4 weeks, to form larvae (infective eggs can survive for years outside). A dog will be infected when it eats these larvae, either through eating food that has been in contact with infected soil, eating a bird or rodent which has swallowed a larva, or by licking its feet clean after exercising on grass. The larvae reach the intestines where the adults live, but they must mature first, so, in puppies, they burrow through the bowel wall, enter the bloodstream, and travel via the liver to the lungs. They are coughed up the windpipe then swallowed, arriving back at the intestines to become adult worms. Some larvae do not complete this cycle in one hop – they form cysts in various places and are triggered to start moving again when a bitch is pregnant (and pass through the placenta to the unborn pups, or to the milk glands) or ill.
RISK TO CHILDREN Toxocara larvae can be swallowed by children playing on infected grassland eg parks, gardens. When this happens, most larvae fail to develop as they are in the wrong host. But occasionally a larva will migrate as in the dog and reach the retina (back of the eye), where it can cause interference with the child’s sight. This is rare, but important, and demonstrates the need to worm dogs regularly, dispose of their faeces properly, and promote good hygiene with children.

WORMING: Dogs should be wormed every 3-4 months, and puppies and pregnant bitches should be wormed more often – ask your vet for details.

TAPEWORMS
The common tapeworm is called Dipylidium, and the segments look like creamy white grains of rice, which may wriggle, around the dog’s back end or in its faeces. The adult worm consists of a large number of segments and those that we see are the ripe ones, full of eggs, detached from the main worm. The eggs cannot infect another animal until they have passed through their secondary host which is the flea or louse. Here the egg grows into a tiny cyst, and when the flea is swallowed by a dog a new tapeworm will develop in the dog’s intestines from this cyst. The adults do not cause harm, but the segments may cause anal discomfort.

WORMING: Dogs should be wormed every 3-4 months, also fleas must be controlled, otherwise the dog can become reinfected by swallowing a cyst-carrying flea.

Other worms do infect dogs. They are all too small to be seen by the naked eye, so must be diagnosed by looking microscopically at faeces samples. A tiny tapeworm called Echinococcus occurs in farm dogs in sheep farming areas, and causes hydatid disease in humans. Regular worming and limiting access to sheep is the effective answer.
No-one, adults or children, can catch worms from a dog. If a child has worms, they are a human type and did not come from the family dog.

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