Advice on worming your pets

Worming your Dog

Why Worm?

Roundworms (including Toxocara canis) and tapeworms are intestinal parasites which can be found in any dog although infection is easily treated. Worms may cause sickness and diarrhoea in young animals. Adult dogs generally show no signs of ill health but still need regular worming.

Human infection (toxocariasis) may occur if mature Toxocara (roundworm) eggs are swallowed, however, it is very rare for anyone to become ill as a result. About 1-2% of healthy adults in the UK already possess Toxocara antibodies which means that they have been exposed to Toxocara eggs or larvae with no ill effects.

Children are more vulnerable to Toxocara infection because they might pick up infective eggs when playing where the faeces from dogs carrying worms have been deposited. On the rare occasions when human disease does occur it usually causes only mild symptoms. In exceptional cases it can cause damage to the eye in young children.

The chances of developing toxocariasis are low. It is estimated that there are only about two new cases of disease due to Toxocara infection per million of the population each year. However, if every owner treated their dog with a worming preparation, and cleared up after their dog, toxocariasis would be virtually eradicated. Newly deposited faeces are not infectious.

Dogs are infected with tapeworms through the ingestion of infected raw meat (e.g. rabbits and other small animals) (Taenia spp) or from the ingestion of fleas during grooming (Dipylidium caninum).

Worming your Dog

Pregnant Bitches and Unweaned Pups

Puppies become infected with roundworms from their mother while in the uterus or through her milk. Pregnant bitches and bitches with young puppies should be wormed frequently.

We recommend that bitches should be wormed before mating, after the first 45 days of pregnancy and after giving birth. They should then be wormed with their pups at 2, 5 and 8 weeks and after weaning. It is also possible to worm the bitch daily from day 40 of pregnancy to 2 days after whelping. This will ensure that the pups have an absolutely minimal worm burden at birth.


It is very important to worm puppies. It is reasonable to assume that all puppies are infected with roundworms (Toxocara canis) and produce larger numbers of eggs. We recommend that puppies are wormed monthly between 2 and 6 months of age.

Adult Dogs

Adult dogs are relatively resistant to roundworms unless they are pregnant. They become infected with tapeworms through contact with fleas and via meat. They should be routinely wormed every 3 to 6 months.

Worming your Cat

What are Tapeworms and Roundworms?

Tapeworms and roundworms are two of the most common intestinal parasites of cats.


These are long flat worms composed of many individual segments which live in the cat intestine. Mature segments (which contain eggs) are shed in the faeces, or sometimes seen around the anus. They look a little like grains of rice and can be mobile.


These are shorter with rounder bodies, and produce microscopic eggs which are shed in faeces. They may occasionally be vomited up from the stomach.

How does my cat get tapeworms?

There are a variety of different tapeworms that infect cats but the two most common are diplydium caninum and taenia taeniaformis. The tapeworm segments shed in the faeces contain eggs which are eaten by an intermediate host (flea larvae or small rodents). When the cat eats an infected flea (when grooming) or kills and eats an infected rodent the life cycle of the tapeworm is completed as the tapeworm develops and attaches to the lining of the cat's intestines. All cats that come into contact with fleas or who hunt are likely to be infected with tapeworms.

How does my cat get roundworms?

The common roundworms of the cat are toxacara cati and toxascaris leonina. With both these worms, infection is by the ingestion of infective eggs or eating another animal (intermediate host) such as a mouse that is itself infected. Toxacara cati may also be transmitted through the milk of the queen (mother) meaning kittens can be infected with roundworms from a very young age. Roundworm infections are extremely common and it is safe to assume that all kittens will be infected.

Can these worms infect humans?

It is possible for humans to be infected with roundworms, both toxocara cati and dipylidium caninum, although the latter is rare. Toxocara cati is a concern, particularly in children, where ingestion of the eggs may result in migration of the worm larvae through the body and potential damage. This is much more of a risk with the dog roundworm (toxocara canis) but can still occur occasionally with toxocara cati.

Due to the potential human health hazard, as well as the possible health of your cat regular worming of cats is important. In addition, careful disposal of litter from litter trays will reduce the risk of passing on other infections (such as toxoplasma) which can occasionally be passed from cats to humans.

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