Contributors: Eran Dvir, Ian Wright

 Species: Feline   |   Classification: Miscellaneous


  • Cats may harbor nematode (roundworm) and cestode (tapeworm) infections, most inhabiting the intestines. These intestinal worms are the mainstay of worm control regimes. However, worms may be present in other organs, especially in cats traveling abroad.
  • There is an increased risk of importation of non-endemic species with the increase in the numbers of animals entering the UK under the Pets Travel Scheme (PETs Pet travel scheme) particularly since there has been a recent relaxation in the rules. Cats traveling abroad will also be at risk of exposure to novel worms such as Dirofilaria immitis  Dirofilaria immitis.
  • Some worms carried by cats have zoonotic potential such as Toxocara cati  Toxocara cati  and Ancylostoma braziliense  Ancylostoma braziliense. Worm control programs should identify cats at high risk of transmitting zoonotic pathogens and risk be minimized accordingly.
  • Worm control centers on suitable anthelmintic regimes and environmental control.
Print off the owner factsheet on Worm control Worm control to give to your client.Print off the owner factsheet All about worms All about worms to give to your client.

Worms commonly infecting cats

  •  Toxocara cati:  the most common nematode of UK and US cats. Kittens are infected by the trans-mammary route and may have patent infection by six weeks of age. Female worms are prolific egg-layers. Eggs passed in the environment develop into the infectious embryonated stage in 2 weeks under optimum conditions. Cats are infected through ingestion of embryonated eggs, especially through grooming, hunting, or eating uncooked meat containing somatic larvae (eating the paratenic hosts). Approximately 10% of domestic cats continue to pass eggs in their feces, though much higher prevalences have been recorded in European feral populations. Zoonotic risk comes primarily from ingestion of embryonated eggs in soil (geophagia), on contaminated objects (pica  Pica) or possibly from fur. Ingestion can lead to visceral or ocular larval migrans Visceral larva migrans with neurological and covert forms of the disease also now being recognized.
  •  Toxascaris leonina  Toxascaris leonina: infection is acquired through ingestion of paratenic hosts or embryonated eggs and cats are normally weaned before they acquire infection. Development takes place in the small intestine where the adult worms remain. Infection is much less common than T.catiin UK and US with prevalences of 5% or less recorded in UK cat populations.
  • Hookworms Hookworm disease: uncommon infections in UK cats but recent studies have shown Ancylostoma tubaeforme  Ancylostoma tubaeforme and Uncinaria stenocephala  Uncinaria stenocephala to be present in endemic foci. The life cycle is direct with larvae hatching from eggs passed in the feces and developing into third stage larvae in the environment. Ancylostoma braziliense and A.tubaeforme are more common in the USA, Western and central Europe. A tubaeforme is the third most common helminth in cats (after T. cati and D. caninum  Dipylidium caninum) in Australia. So Ancylostoma species may be encountered more frequently in traveling or imported cats. A.braziliense is a significant zoonosis with the L3 larvae causing the creeping skin eruption known as cutaneous larval migrans. Optimal development of hookworm larvae takes place in warm, moist, sandy soil that is sheltered from direct sunlight. Therefore, most cases of hookworm disease occur during late spring, summer and early autumn.
  •  Aelurostrongylus abstrusus   Aelurostrongylus abstrusus: thought to be endemic in the UK but recent prevalence data is lacking. Transmitted through the ingestion of Mollusc and amphibian intermediate hosts, infection can lead to bronchitic signs. This worm is sporadically distributed throughout Europe.
  •  Ollanulus tricuspis and Physaloptera  Physaloptera infection species are worms that can inhabit the feline stomach. Ollanulus infections occur only sporadically in the US and are more common in free-roaming cats and those housed in multiple-cat facilities. Cats become infected by ingesting the parasite-laden vomitus of another cat.
  •  Dirofilaria immitis Dirofilaria immitis: cats have some innate resistance to infection and prevalence in cats is often around 10% of the level in dogs in endemic countries. D.immitisis not endemic in the UK but cats traveling abroad may become infected through mosquito bites.
  • Tapeworms: cats may acquire Taenia spp Taenia taeniaeformis tapeworms through hunting and Dipylidium caninum  Dipylidium caninum though ingestion of fleas and lice. Exact prevalence data on tapeworm infections is lacking as fecal egg-counts are unreliable for detecting tapeworm infections and post mortem prevalence studies and post mortem studies are scarce but tapeworm infection overall in hunting and flea infested cats is common. Echinococcus multilocularis  Echinococcus multilocularis does not occur in the UK, but is endemic across a large area of central Europe. The intermediate hosts are small rodents and the fox acts as a definitive reservoir host. Although dogs and cats can be infected, cats are less susceptible hosts, carrying fewer worms and allowing fewer to reach patency. E.multilocularis is the cause of the serious zoonosis alveolar echinococcosis.

Deworming frequency

  • Disease in intestinal worm burdens is a function of numbers present and deworming every 3 months is normally sufficient to prevent significant disease. This frequency may need to increase to monthly regimes in hunting cats or decrease in indoor cats where good hygiene is maintained.
  • Deworming every 3 months reduces Toxocara Toxocara cati spp ova shedding and is therefore a minimum requirement in cats with access to the outdoors, hunting or in contact with children or immune suppressed adults. Where these activities are common or where cats are communing with very young children whose hand hygiene may not be adequate then frequency should be increased to monthly deworming. This will decrease ova production by over 90%. 
  • Treatment of kittens may start later than pups as there is no trans-placental transmission. Treatment should start at 3 weeks of age, repeated at 2 weekly intervals until 2 weeks post weaning and then monthly until 6 months old. This is to eliminate Toxocara egg shedding from trans-mammary infection and significant populations establishing in the intestine.
  • Avermectins (Moxidectin Moxidectin, eprinomectin Eprinomectin), tetrahydropyrimidines (eg oxantel, febantel Febantel), emodepside and benzimidazoles such as fenbendazole Fenbendazole   are all effective in treatment of T.cati. Praziquantel Praziquantel is and effective and broad spectrum tapeworm treatment.
  • Cats traveling abroad to heartworm endemic areas should be treated with a licensed macro cyclic lactone such as selamectin Selamectin, milbemycin oxime Milbemycin oxime, eprinomectin or moxidectin a week before travel and the monthly until a month after return to the UK. Monthly praziquantel should also be administered to cats spending more than a month abroad as a precaution against  Echinococcus multilocularis infection.

Environmental management

  • Flea/louse/fly control  Flea: control:  to prevent D.caninum transmission and to prevent mechanical transmission of eggs
  • Picking up of cat feces: to reduce environmental contamination with ova and larvae. As most ova take few weeks to be transformed into an infectious stage, regular and frequent picking is of utmost important and should be beneficial.
  • Good hand hygiene: to prevent zoonotic transmission of T.cati eggs
  • Thorough cleaning/disinfection of catteries, litter trays and runs: to prevent build-up of infectious environmental stages. However, once an infection in the soil has been established many of the eggs become highly resistant and toping the floor with fresh gravel might be required.
  • Preventing or reducing hunting behavior: if practical.
  • Eliminating paratenic hosts: especially rodents that might be attracted to the food in the cattery.