A Guide to the different types of pet worms

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There are several species of worm which can affect cats and dogs and also pose significant health threats to people. The majority of puppies and kittens are born with roundworms or can be infected through their mothers’ milk. Most animals do not showing outward signs unless they are carrying a significant worm burden. There are two different groups of worms which are classified according to appearance and their life cycle.


These include hookworms, whipworm, heart worm, lungworm, and bladder and liver worms. The most common roundworms in Britain are Toxocara sp.

Toxocara canis infects dogs and puppies and can be passed on to humans causing organ damage and possibly blindness through the migration of the larvae. Dogs are able to contract the worms through any of three routes.

Before birth: Larvae migrate from the bitch’s muscles to the uterus from approximately day 42 of pregnancy.
Eating infective eggs: these will have been passed out in the faeces and can be transferred onto fur (or clothing) allowing the dog to ingest the eggs whilst grooming. Eggs can remain infective in the environment for up to 2 years if conditions are suitable
Eating an intermediate host: This transfers the worms directly to the intestine of the dog.


Tapeworms are flat and consist of many segments. It is more common to see individual segments then the whole worm. These look like moving grains of rice and are found around the rear end.

There are 3 main types of tapeworm common in the UK

Echinococcus granulosus – Transmitted through eating infected sheep. This can be transmitted to humans where the parasite forms a hyatid cyst usually on the liver or lungs.
Taenia sp. Contracted through eating raw infected meat e.g. offal or catching live prey.
Dipylidium caninum - The most common tapeworm in the UK. Transmitted through infected fleas which are eaten when grooming.


Hookworms are occasionally seen in the UK but are predominantly found where large numbers of dogs live together such as hunt or racing kennels.


Lungworm is usually contracted through the cat or dog eating an infected snail or slug. Infection at present is mostly located in Southern England and south Wales.


Whipworm are bladder and liver worms which are rarely seen in the UK

Heart worm

Heart worm is not found in the UK but should be treated for if visiting warmer countries. It is endemic from the Mediterranean region of France southwards.

By Ardent Pets

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