It depends what you mean by “best”! However, cats can suffer from a wide range of worms, so it’s always wise to make sure you’re using the right product, at the right time. To begin with, we’ll have a look at some of the creepy crawlies that can infest your beloved pet, and then we’ll look at how to kill them!

Wriggling worms:

The group of worms we’re usually most concerned about are the roundworms. As the name suggests, these are quite fat worms, looking a bit like earthworms (but not closely related at all). They are most commonly contracted from larvae shed in other cats’ faeces and picked up from the environment. In cats, roundworm infestations can cause weight loss (because the worms are eating the cat’s food!), diarrhoea and sometimes vomiting.

Itchy worms:

The next group are the tapeworms. These are long, ribbon-like worms, made up of a long string of segments (called “proglottids”) behind a head that hangs onto the gut wall. These can cause all the same symptoms for the same reasons, however, there’s a more common sign that your cat may have tapeworms – an itchy bottom.

Tapeworms are usually transmitted through a cat’s prey (rats, mice etc) or through other parasites (like fleas and lice – if the cat catches a flea while grooming, they’ll crunch it, and then they become infected with the tapeworm). So to control them, you need to make sure you’ve got good flea control as well!


Yes, cats can get lungworms too! However, they’re not the same sort as dogs get. Cats usually develop a worm called Aelurostrongylus abstrusus. These live in the lungs, laying eggs which are coughed up. The most common symptoms are coughing, mucus build-up in the chest, and occasionally difficulty breathing (in very heavy infestations).

These worms are spread when cats drink water, or eat prey (birds, mice, rats etc.) that are infected with the worm larvae. Lungworms are often quite hard to kill, but fortunately they only rarely cause serious disease.

Horrible things! So how do we kill them?

There are a LOT of different wormers on the market nowadays, so in this section we’ll look at some of the more common preparations*.

Homeopathic wormers and nosodes

Sadly, there is no evidence that these products have any effect on worms one way or the other. We do not recommend them as a solution to worm problems or as a preventative.

Herbal wormers

These are widely available now, and some of them certainly can work. The trouble is that using a herbal wormer is often fundamentally unreliable – those herbs that are effective contain pretty much the same chemicals as the pharmaceutical tablets, but in widely varying doses – because the plants don’t do quality control on what they put in their leaves! Although there is no reason that herbal wormers can’t work, we do see cases regularly where they have failed, resulting in severe infestations and sometimes a very sick cat. As a result, we wouldn’t recommend herbal products for treatment of an infestation, and would advise caution if you are using them as a preventative.

Over the counter pet shop and supermarket tablets

These are usually very, very cheap, so we understand why you’d be tempted by them! However, although they often contain real and effective ingredients, in practice they tend to be limited in which worms they kill (for instance, Bob Martin’s Clear Wormer Spot On kills only tapeworms, whereas their Clear Wormer Granules kill only roundworms), and often are of only limited effectiveness. Some of these (e.g. Beaphar Worming Syrup) are really popular with owners because you can see the worms being passed… but that happens because the worms haven’t been killed, just paralysed (the active ingredient is piperazine which a paralytic, not a worm killer). As a result, it’s probable that there are some left inside to carry on breeding.

Vet and pharmacy-only tablets and liquids

The liquids are generally aimed at kittens, so kill roundworms only (e.g. Panacur, containing fenbendazole). Most of the tablets, however, are effective and contain a mixture of ingredients to kill different types of worms. For instance, Drontal contains pyrantel embonate to kill roundworms and praziquantel to kill tapeworms. Because they are more effective, there are legal controls on their sale, which is why our receptionists can only sell them if there is someone with suitable qualifications in the building (a vet, a pharmacist, or an AMTRA-trained SQP).

Prescription-only worming tablets

These are highly effective, and very safe. They usually contain a range of different substances (typically milbemycin oxime against roundworms and praziquantel against tapeworms). In general, they’re also smaller and easier to give than the bigger non-prescription tablets!

Prescription-only spot-on medications

There are now a range of different spot-ons that will kill worms. Many (e.g. the popular moxidectin/imidacloprid combination) will only kill roundworms, but there are some (e.g. Emodepside/Praziquantel mixtures) that will kill roundworms and tapeworms equally effectively.

If you need advice on worming, feel free to give us a ring – our vets will be able to help you choose the most effective solution for your cat!

* NB – under UK law, it is illegal for us to name any prescription-only brands in this blog, so where necessary we’ll use the drug’s generic or chemical names.