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You can read or listen to our modules. There is a play button in each heading so you can listen while you read. Or you can listen to the whole module in one go or download it as a podcast. You'll find a play and download button for the whole module at the bottom of this page. At the end of the module there is a quiz, so you can test your knowledge and receive a CPD certificate. You will have to hit the play button on the quiz video and enter your name and email address before you start the quiz.

Several types of parasite can affect cats in the UK. The main aims of a parasite control programme and use of parasiticide medicines are to control the parasites that can cause or transmit significant disease in cats, or be transmitted to humans. In the UK these are: fleas; roundworm; ticks; tapeworm; and lungworm. By the end of this module you will:

  • know the five most important parasites that affect cats
  • understand why cats are at risk
  • understand why parasite protection is important for humans and cats
  • know the basic parasite protection cats should get.

Fleas and roundworm can affect all cats anywhere in the country and so all cats need protection against fleas and roundworm.

The cat flea (Ctenocephalides felisare) is a very successful parasite due to its rapid reproduction, and its ability to persist in a pupal stage in the environment, and to parasitise a wide range of animals including cats, dogs, rabbits, foxes and hedgehogs. Many owners believe that fleas are only a summer problem, but fleas can be active all year round perhaps because of central heating and warmer winters.

Flea control is important because fleas can cause flea allergy dermatitis, irritation, and anaemia in heavy infestations. In addition, fleas transmit the flea tapeworm Dipylidium caninum. They can also transmit bacterial diseases to cats. For example, Bartonella henselae, which can be transmitted to humans and cause cat scratch disease. 

Fleas are present across the whole of the UK and may be brought into homes on pets and on pet owners’ or visitors’ clothes. It is therefore practically impossible to avoid exposure, which in turn can lead to household infestation. This is why parasite specialists recommend that all susceptible pets in the household should be routinely protected against fleas. As it can take 3 months or more to get rid of a flea infestation, prevention is usually better than cure. 

There is a wide range of parasiticide medicines for controlling fleas. See the module "Making sense of flea and tick products".

Cat roundworm (Toxocara cati) is a worm that lives in the intestines of cats. It can be transmitted to humans and potentially cause serious disease, and so it has significant public health implications. Roundworm is present throughout the UK.  Most kittens will become infected via their mothers' milk (see the module on kitten worming). Cats may also become infected by ingesting roundworm eggs in the environment or through eating infected prey such as rodents.

Roundworm infection in cats is lifelong because roundworm larvae remain dormant in the cat's body tissues. This does not usually affect the cat, but eggs are intermittently shed in the faeces, helping the spread of roundworm. People can become infected through ingestion of eggs in contaminated soil, or on unwashed fruit, vegetables and toys, or through transfer of eggs from the coats of pets. Children aged 2-4 years are most commonly affected by roundworm infection. Roundworm can be controlled by regularly worming cats.

Washing hands before eating and covering sand pits when not in use will help prevent infection and spread of roundworm. Cats should also be wormed regularly with a wormer that is effective against roundworm, to reduce the shedding of roundworm eggs. Worming every 3 months is sufficient for most cats, but monthly worming is recommended for hunting cats and for pets that have contact with young children and immunosuppressed people. 

There are many non-prescription wormers for controlling roundworm. They also usually cover tapeworm too. 

The cat's lifestyle might expose it to these other parasites.

Ticks can attach to cats leading to diseases such as dermatitis, bacterial infection and, in severe cases, anaemia. Ticks also have the potential to carry bacterial diseases such as Lyme disease and babesiosis and although not affected by these, cats can help spread them by transporting infected ticks. A flea and tick product should be used regularly on cats that are frequently exposed to ticks. 

Two types of tapeworm predominate in UK cats: Taenia taeniaeformis and Dipylidium caninum.

Cats become infected with Taenia taeniaeformis through eating infected rodents. However, cats are usually unaffected, even by large numbers of worms, and this worm does not affect humans. People do not usually like the idea of their cat having worms and so if tapeworm segments are seen around the cat's anus, monthly tapeworm treatment might be needed.

Fleas and lice can carry the tapeworm Dipylidium caninum. Infection occurs either by grooming or by eating infested prey, but infection is usually well tolerated in cats. The tapeworm can be spread to humans but this is rare and does not usually cause symptoms. Control of this tapeworm depends on flea control.

There are many non-prescription wormers for controlling tapeworm. They usually also cover roundworm.

The lungworms that affect cats are not the same as those that affect dogs. The main lungworm affecting cats in the UK is Aelurostrongylus abstrusus. Preventing exposure to lungworms is difficult in outdoor cats.

The lifecycle of A. abstrusus involves slugs or snails as intermediate hosts. Larvae pass out in the faeces of cats into the environment and penetrate slugs and snails. These might be eaten by various animals including reptiles, amphibians and birds, which in turn can pass on the infection to cats that eat them.  Hunting cats are therefore at greater risk of lungworm infection than non-hunting cats. Adult worms live in the lung tissues, and do not always cause any problems to the cat, but infection can cause a mild to moderate chronic cough, sneezing, wheezing, nasal discharge and breathing difficulties.  

Non-prescription medicines containing fenbendazole (the brands Granofen and Panacur) are licensed for the treatment of this lungworm in cats.

The following questions will help determine the appropriate level of roundworm protection for a cat and the need for protection against the other main parasites – ticks, tapeworm and lungworm, as well as fleas.

Question 1Is your cat in regular contact with young children, or a person with a condition or on medication that suppresses the immune system? If so, monthly rather than 3-monthly roundworm treatment is recommended.

Question 2Have you ever found a tick on your cat? A history of tick attachment strongly suggests that the cat’s lifestyle exposes it to ticks. A product effective against fleas and ticks is recommended,

Question 3Does your cat go outdoors/does it hunt. Unless the cat remains indoors it is likely to be exposed to lungworms. Cats that hunt might also be at increased risk of tapeworm infection. Treatment with a product that controls lungworms and/or tapeworm may be needed.

If using non-prescription products, two separate products are needed to cover fleas and ticks and worms. Some prescription-only products cover all the key parasites in one product. See the modules on "Making sense of flea and tick products" and "Making sense of wormers" for more on product choice.

There are certain things you should check before selling a parasiticide medicine.

  • what parasites the product is licensed to cover. Although different products might have the same ingredients, they might have different licensed uses.
  • what species it is intended for
  • that the product is suitable for the animal's age 
  • that the dose is correct (for the animal's weight)
  • how often it should be used
  • the expiry date

Remind the owner to read the information in or on the package before using it.

Practical exercise

Become familiar with the parasiticide products stocked for cats. What different formulations can you offer (e.g. collar, spot-on, tablets)?


You can listen to a complete podcast of the module by using the play button below or use the download link on the right hand side of the player to download the podcast to your mobile device.

Test yourself

To do the CPD quiz and receive your certificate, you will need to hit the play button on the player below and enter your name and email address before you start.


Committee for medicinal products for veterinary use, 2008. Guideline for the testing and evaluations of the efficacy of antiparasitic substances for the treatment and prevention of tick and flea infestation in dogs and cats.

Dryden MW et al. Control of fleas on naturally infested cats and dogs and in private residences with topical spot on applications of fipronil and imidacloprid. Vet Parasitol 2000; 93: 69-75.

Elsheika HM et al. Updates on feline aelurostrongylus and research priorities for the next decade. Parasites Vectors. 2016; 9: 389.

ESCCAP. Worm control in cats and dogs. ESCCAP guideline 01 second edition. September 2010.

ESCCAP. Ectoparasites part 1: control of parasitic insects and ticks in dogs and cats. Guideline 3, March 2009.

Fisher M. Toxocara cati: an underestimated zoonotic agent. Trends Parasitol 2003; 19: 167-70.

Halsby K et al. Epidemiology of toxocariasis in England and Wales. Zoonoses Public Health 2016; Feb 20. doi: 10.1111/zph.12259.

Holland CV. Knowledge gaps in the epidemiology of Toxocara: the enigma remains. Parasitology  2015. doi:10.1017/S0031182015001407.

Overgaauw PAM, Van Knapen F. Veterinary and public health aspects of Toxocara spp. Vet Parasitol 2013; 193: 398-403.

Wright I et al. The prevalence of intestinal nematodes in cats and dogs from Lancashire, north-west England. J Small An Pract 2016. doi: 10.1111/jsap.12478

Wright I, Wolfe A. Prevalence of zoonotic nematode species in dogs in Lancashire. Vet Rec 2007; 161: 790-1.