How do I treat my cat for worms?

What are the main kinds of worms that infect cats?

The two main types of worms that infect cats are roundworms and tapeworms. Many cats don’t show signs of having worms, but large numbers can cause weight loss, vomiting, diarrhoea and the failure to grow and develop.

What are roundworms?

Roundworms are the most common intestinal parasites in cats. There are two different types, Toxocara cati and Toxascaris leonina. Eggs from these worms are passed in the faeces and can be eaten (ingested) by other cats. Eggs can remain infective within the environment for months to years! Infection can also be passed by rodents (an intermediate host) that have eaten eggs and in turn are eaten by a cat.

Toxocara cati is also passed through the milk of the queen (mother) to her kittens. Whenever a queen is infected with roundworm some immature forms of the roundworm (larvae) remain dormant in certain tissues in the body. This causes no harm to the queen but when she gives birth the larvae migrate to the mammary glands and are excreted in the milk. This is a very common route of infection and we can therefore assume that most kittens will be infected with Toxocara cati. It is estimated that 10% of adult cats also shed this worm in their faeces. T leonina is not often seen in the UK.

Kittens are particularly susceptible to roundworms and are often infected from birth.

What are tapeworms?

Tapeworms are long flat worms composed of many segments. Segments containing worm eggs are passed in the faeces. These segments resemble grains of rice in appearance and can sometimes be seen on the hair around the anus of the cat, in the faeces and on the cat’s bed.

The most common types of tapeworm that infect cats are called Dipylidium caninum and Taenia taeniaeformis. Dipylidium is transmitted to cats by fleas. Immature fleas (larvae) ingest the eggs of the worm and infection is passed on to a cat when it swallows an infected flea during grooming. It should therefore be assumed that any cat infected with fleas also has Dipylidium, and vice versa.

The other type of tapeworm, Taenia taeniaeformis, is passed on to cats by small rodents (rats and mice). Worm eggs are eaten by rodents and passed on to cats when they hunt and eat an infected rodent. This infection therefore occurs in any cats that hunt.

Don’t forget to buy a flea product to eliminate the fleas and their lifestages from your carpets and soft furnishings, and pet bedding should be washed regularly.

How do I treat worms?

Worms are impossible to prevent. There is no preventative treatment that will stop your cat from becoming infected. However, there are a number of very good products that will kill worms. Remember, however, that most oral worming products are effective at the time of use only, and they do not have a prolonged action.

For kittens, creams or syrups, which are available both from pet stores and vets, are usually the most suitable and easiest to administer. Treatment needs to be every two to three weeks to begin with, lessening to once a month at three to six months, and thereafter once every three months.

Adult cats will also pick up worms from the wider environment, but, having a more developed immunity, do not need to be treated as frequently as kittens. Once a quarter is sufficient for most family pets.

People and worms

Roundworms can infect humans. In a few very rare cases, children who ingest the eggs can suffer eye damage or blindness as the worm larvae move through the body causing tissue damage, so it’s important to control infection of your cat.

Which worming products should I use?

Some worming medications are effective against both roundworm and tapeworm, while others are only effective against one or the other. It’s important to chose the right product for your cat.

Many worming medications are now available such as liquids, pastes and granules as well as injections from your vet and spot-on treatment. Your vet is the best person to ask for advice on the correct treatment. Here are the most commonly used worming medications, all of which are very effective:

Panacur (Intervet) Contains fenbendazole. Active against gastrointestinal roundworms, lungworms and Taenia tapeworms. Licensed for use in kittens from 2 weeks of age and for use in pregnant queens. It is available in the form of granules, liquid, paste and a newly formed palatable tablet.
Drontal cat (Bayer). Contains pyrantel (active against roundworm) and praziquantel (active against tapeworm), in a tablet form.
Droncit injection (Bayer). Contains praziquantel. Active against tapeworm only.
Droncit spot-on (Bayer). Contains praziquantel. Active against tapeworm only.
Stronghold spot-on (Pfizer). Contains selamectin. Active against roundworm only. Also active against ear mites (Otodectes cynotis), mange (Sarcoptes scabei) and fleas.
Milbemax for cats and Milbemax for small cats and kittens (Novartis). Contains milbemycin oxime (effective against roundworms) and praziquantel (effective against tapeworms). Very small and palatable tablets which make them easier to dose cats with.
Profender spot-on (Bayer) Active against tapeworm, roundworm and hookworms.

Read our advice about worming treatment options.