Worms in Cats

By E.G.D.McCarrison BVMS MRCVS

Vet of the Year 2007

It may be distressing to be told that, at some time during your cat’s life, he or she will almost certainly be affected by worms. Nevertheless, this is an unfortunate fact of feline life; and it is vital for your own health as well as for that of your cat – that you introduce regular worming into your ‘Cat Care’ regime.

So What Are Worms?

There are some 8 different types of intestinal worms which can infect your cat, and some can be spread between cats and people. Roundworms and Tapeworms are the most common. Both of these types spend their adult life in the cat’s bowels, and in small numbers they are not very harmful. However, in large numbers they can cause suffering, illness and even death.

Roundworms (Toxocara Cati and Toxascaris leonine)

As the name suggests, roundworms resemble the worms we see in the garden – although much thinner. They are long, circular in cross section (not unlike spaghetti) and usually pointed at each end. Their eggs are passed out in the cat’s faeces, but being microscopic there is often no evidence that they are present.

When they are born many kittens will get these worms from larvae in their mother’s milk.

Mice, voles, shrews and birds can all be infected with roundworm larvae, and when the prey is caught and then eaten by the cat the eggs hatch in the stomach.

In addition to regular worming (which we deal with later), it is important to clean litter trays regularly due to the transference of eggs in your cat’s faecal matter onto its paws and coat – which are subsequently swallowed whilst the cat grooms itself.

Tapeworms (such as Dipylidium caninum and Taenia taeniae formins)

Tapeworms are often much longer than roundworms. They hook into the lining of the cat’s bowels and develop long ribbon-like bodies, the ends of which become egg sacs which break off and pass out of the back passage. You will often see these segments in the cat’s faeces or on the hair around the cat’s bottom. When dry the egg sacs resemble grains of rice.

These particular worms are much more of a problem in older cats – particularly those which hunt, or are periodically infected with fleas. The life cycle of a tapeworm involves a second intermediate ‘host’; and this is either a flea or (as with roundworms) a small mammal such as a mouse. The most common is the flea tapeworm (Diplidium) which is acquired by the cat swallowing fleas infected with the tapeworm larvae. A single such flea can infect your cat, and hence it is extremely important that your ‘Cat Care’ regime also includes regular and effective flea control.


The symptoms of worm infestation are negligible in the early stages, which is why regular worm control is essential. By the time symptoms do appear your cat’s health has already been damaged.

The signs of roundworms are primarily vomiting, diarrhoea, weight loss, a dull coat, and lack of energy. In severe cases a swollen/distended tummy (pot belly) – which is particularly noticeable in kittens.

Many cats will not show any symptoms of tapeworms. The most common are an increased hunger, dragging the bottom along the ground due to the irritation caused by the worm, and more time spent washing its anal area. As mentioned earlier, the appearance of egg-filled segments – which look like small grains of rice – around the cat’s bottom.

Hookworms (Ancylostoma tubaeforme) are blood-sucking parasites that live in the small intestine and are becoming an increasing threat mainly due to the increasing fox population, so many of which are carrying the infection. The eggs are deposited on the soil in the foxes faecal matter and hatch there, being picked up by the cat’s feet. In addition to the same symptoms as roundworm, dark stools (caused by bleeding – which can lead to anaemia) and diarrhoea are also a typical sign.

Can humans be infected by the worms?

Some types of worms can be spread between cats and people. For example, the eggs from some of the roundworms can be ingested accidentally, with the result that the egg may hatch and the larva then migrate out of the bowel and lodge in the tissues of our bodies. Whilst this is not common, there are reports of a few children having eaten the eggs and suffering eye damage and even blindness as a result. As the eggs are also left in the soil when an infected cat does its toilet, it is always advised to wear gloves when gardening.

The common tapeworms are much less likely to infect humans, however yet again this can occur, and is most likely to be the result of an infected flea being swallowed.

Treatment and Risk Reduction

It is important to understand that you cannot actually prevent worms; and that they are so prevalent that the vast majority of our cats will be infected. However, with regular and effective worm control as an integral part of your ‘Cat Care’ regime you are able to get rid of those worms which are present at the time of treatment – hence removing the threat of the illnesses and suffering to which we have referred earlier.

There is a multitude of different worming products (for the different types of worms) available on the market from pet shops, supermarkets, and on the internet; and it can therefore be very difficult, and often confusing, to be certain that you are using the right ones. Some treatments are effective against roundworm and tapeworm, whilst others are only effective against one or the other.

Not only is the range of products huge, but so also are the ways of administering them. Some excellent ones are still in tablet form. Other effective ones come in spot-on form, or as pastes, powders, syrups, or with injections by your vet. As regular worm treatment is so very important to your cat’s wellbeing it is therefore a good idea to have a word with your vet before deciding upon the right ones to use for your particular cat.

In my experience cats do not like being wormed, and some are extremely difficult to treat with tablets – even the palatable ones. For this reason, I personally believe that the ‘spot-on’ treatments are by far the easiest to administer.

A good ‘spot-on’ treatment can also control fleas at the same time, and although tapeworm has then to be treated separately the flea treatment itself will reduce the incidents of tapeworm eggs being ingested by your cat via a flea. You usually apply a combined flea and worm ‘spot-on’ treatment monthly, and then the separate tapeworm treatment every two to three months.

Many good flea ‘spot-on’ treatments also control roundworm and hookworm. This combined treatment is useful because it reduces the incidents of tapeworm eggs being ingested by your cat via a flea – as well as treating the roundworms and hookworms. The treatments are usually applied monthly. However, if using these you will still need to apply a separate tapeworm treatment every two or three months.

Bayer has a product called ‘Profender’ which is a spot-on treatment for roundworms, hookworms AND mature tapeworms, so this just leaves the fleas to be treated.

All this may seem a little confusing, especially as some products which control fleas contain a similar drug to those which control worms, and both types should not be used on the same cat for fear of an ‘over-dose’ of similar drugs. This is another very good reason to take advice from your vet.

In general practice I frequently saw cats upon which the owners had, with the very best of intentions, used commercially available treatments but with no success – either through misuse, difficulty in administration, or the lack of effectiveness of the product itself. As a result the cats were not being effectively wormed. For this reason I would repeat my recommendation that you take advice from your veterinary surgery.

Additional risk reduction precautions include wearing gloves when gardening, ensuring that litter trays are regularly disinfected, and that your cat’s bedding is washed as often as possible. If children play in a garden to which cats have access then ensure that the youngsters always wash their hands afterwards.



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"The cat is a dilettante in fur"

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