Internal parasites


The two groups of internal parasites most commonly found in cats are tapeworms and roundworms, both of which live in the intestinal tract (the gut).


Tapeworms are flat, tape-like worms that are common in the bowel of most mammals, the cat included.

What are the signs of tapeworms?

Tapeworms consist of a scolex (head), which attaches itself to the wall of the gut by either suckers or hooks, and a series of segments containing eggs. These segments break off and are passed out with the faeces. They are sometimes visible in the faeces, around the cat’s anus or in bedding. They resemble small grains of rice and may move.

Tapeworm lifecycle

In the environment, the segments disintegrate, releasing eggs. The eggs themselves are not infectious to cats. They have to pass through a host to be able to complete their life cycle. The host varies for different types of tapeworm, but a cat will become infected when he ingests an infected host such as a flea or rodent.

As one type of tapeworm is transmitted by fleas, it should be assumed that a cat infected with fleas also has tapeworm and vice versa.

The worms live by absorbing pre-digested food in the bowel of the cat. They are rarely harmful except where heavy infestations cause obstruction of the gut or weight loss.



Roundworms are the most common intestinal parasite in cats. Adult roundworms look like a white earthworm. They can grow up to 10cm in length.

Roundworm lifecycle

Adult worms live in the cat’s intestine and feed on digested food. Their eggs are passed in the faeces; the entire worm is not usually passed. The eggs are not infectious to other cats when first passed but become infectious after a few days when they develop into larvae. They may remain infectious for years until eaten.

Roundworms can be passed through the milk of the queen (mother) to her kittens. This is a very common route of infection so we can assume that most kittens born to a mother with roundworm will be infected.

How can worms be treated and prevented?

Vets provide the only effective treatment for worms in cats. Some worming medications are effective against both roundworm and tapeworm, while others are only effective against one or the other.


Information on worming kittens is currently limited. Most guidance is based in studies carried out in puppies. However, puppies can become infected while in the womb, whereas kittens only become infected via the mother’s milk.

Cats Protection recommends that if there is concern that a mother cat has worms which may have been passed to her kittens, they should be treated with a suitable product from four weeks of age. Veterinary guidance should be sought prior to treatment.


From six weeks of age, healthy kittens will require monthly treatment against roundworms. From six months of age, they will generally require treatment against roundworms and tapeworms every three months. 

Kittens should be weighed prior to every worming treatment to ensure that the correct dosage is administered.

Adult Cats

Adult cats need to be treated with a drug active against both roundworms and tapeworms every two to six months. The precise frequency of treatment recommended will vary slightly depending on the individual cat, eg whether the cat hunts and is regularly treated for fleas.

Veterinary guidance should be sought before deciding what to use and how often.

Why control worms?

Heavy burdens of worms in cats can cause weight loss, vomiting, diarrhoea and/or failure to thrive, particularly in young kittens.

Roundworms can occasionally infect, but provided the litter tray is emptied and cleaned daily, there is no risk from the fresh faeces.

Tapeworm infection of humans is not common but can occur occasionally, usually in children who have ingested a flea which contains the larvae of the tapeworm.

Worming your cat regularly and keeping it treated against fleas will ensure the risk is absolutely minimal.

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