What’s what with worms

Worried about worms? Learn the difference between the different worms that can affect your pet.


There are a number of different worms which can infest dogs and cats, including roundworm, hookworm and tapeworm. Although they may not be visible, our pets are commonly infected with worms.


Toxocara spp. & Toxacaris leonina

This is most common type of worm to affect dogs and cats. Studies show that up to 30% of dogs and 70% of puppies are infested with Toxocara canis1,2 and a recent Irish study showed that 32% of cats were infested with Toxocara cati3.

Pets can become infected in a number of ways: by eating soil contaminated with eggs, by hunting and by eating rodents.Puppies and kittens can be infected from their mother’s milk.


Roundworms can lay up to 200,000 eggs per day!

Infection does not usually cause symptoms in adult dogs and cats, but can cause serious disease in puppies and kittens, including weight loss, diarrhoea and respiratory problems.

Human risk:

Toxocara spp. worms (AKA roundworms) can affect humans if eggs are accidentally ingested. Children are most at risk, as they may play in areas such as sandpits and gardens where worm eggs are commonly found. The parasite can cause a variety of problems, including damage to the liver, lungs or eyes.

Regular treatment will help to protect your pet and this will help to protect your family too.

 Kids in Sandbox


Ancylostoma tubaeformeA. BrazilienseUncinaria stenocephala

Hookworms are relatively uncommon in pet dogs and cats in Ireland.

Infection can occur through eating larvae from the environment. The adult worms in the intestine feed off blood and some blood may pass in the faeces which typically turns faeces a blackish colour.


Tapeworms are less common than roundworms, and do not usually cause symptoms. The two main types of tapeworm found in pets in Ireland are Dipylidium caninum (flea tapeworm) and Taenia species.

Dipylidium caninum (flea tapeworm)

Pets become infested by ingesting fleas. Good control of fleas will prevent this tapeworm.

Taenia species.

Pets become infested by hunting and eating rodents or eating uncooked meat / carcasses. If your cat regularly hunts AND eats rodents, ask your vet about treatment for Taenia spp. tapeworms.



  1. Overgaauw et al., Veterinary and public health aspects of Toxocara spp. Veterinary Parasitology 2013, 398–403.
  2. Helminthoses digestives des carnivores domestiques. EMC, Veterinaire, Gastroenterologies, 0300, 2010.
  3. Power, C. et al. The prevalence of gastrointestinal and cardio-respiratory parasites in stray dogs and cats in Ireland. Poster presentation at ESCCAP Europe Congress, April 2018.



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