Intestinal Worms in Dogs and Cats

There are several different types of internal parasites that can affect your cat or dog. This blog looks at the four most common types of intestinal worms, which primarily affect the gastrointestinal system. Left untreated, intestinal worms can cause serious illness in your cat or dog, particularly kittens and puppies. In this blog, we’ll go through the different types of intestinal worms, explaining how they affect cats and dogs, how they’re picked up, and what you can do to protect your pets from them.

What are Intestinal Worms?

In the UK, there are four main groups of intestinal worms that can affect your cat or dog.

For dogs, the most dangerous type of worm is roundworm, but tapeworm, whipworm and hookworm also pose a risk. Cats are usually only at risk of roundworm and tapeworm.

Intestinal worms live in the inner organs or bloodstream of their host and infect your pet’s gastrointestinal system.

Each different type of worm affects your pet differently, and they can be transmitted in different ways.


Roundworm is the most common type of intestinal worm in both cats and dogs. They are long and white, a bit like spaghetti, and can grow up to 15cm long.

Infection starts when roundworms are ingested by the dog or cat. They live in the animal’s intestinal tract, but some types of roundworm will also migrate into other parts of the body, such as the lungs, as part of their life cycle. They absorb nutrients from their host, and pass their eggs through their host’s stools to complete their life cycle.


Hookworms are short parasites that attach themselves to their host’s intestinal wall. They then feed on the host’s blood, causing severe anaemia in many cases. Hookworms are particularly dangerous to puppies and kittens because of the volume of blood they consume.

Luckily, hookworms are not common in the UK, but they are present in Europe.


Also uncommon in the UK, whipworms are longer with a thicker end. They live in the large intestine. Since they don’t extract as many nutrients from their host, they are not as dangerous as other types of worms, and pets rarely show symptoms.

However, they can sometimes burrow into the intestinal tissue, which can cause damage to the intestines and result in bloody diarrhoea.


Reaching up to half a foot in length, tapeworms are long and flat. Tapeworm latches onto the wall of the small intestine with their six rows of tiny teeth to absorb nutrients as food is ingested.

They are composed of many segments, and will release the mature ones which contain eggs, allowing them to pass through their host’s faeces. These mature segments appear like grains of rice and can sometimes be seen on your pet’s bottom, in their bed, or in their stools.

How Do Dogs and Cats Get Worms?

Pets can become infected by intestinal worms in a number of ways. These include:

Ingesting Contaminated Soil

Some types of intestinal worm, including hookworm, whipworm and roundworm, can be passed on to cats and dogs if they eat soil containing worm eggs. Hookworm and roundworm eggs can end up in soil when an infected animal goes to the toilet there. The eggs themselves can survive for a long time in the environment before infecting other animals. Cats and dogs might accidentally ingest soil while grooming, or when eating something from the soil.

Walking on Infected Soil

Dogs and cats can be exposed to hookworm larvae by walking over or lying down on contaminated soil.

The stool of an infected animal contains microscopic hookworm eggs which can hatch into larvae and stay alive in soil for several months. If a cat or dog walks over or lies on infected soil, hookworms can infect them by burrowing through their skin.

Hookworm is the only type of worm that can be passed on this way.

Via Intermediate Hosts

All four types of intestinal worm can be contracted by eating an infected animal, known as an ‘intermediate host’.

For example, a mouse might eat roundworm eggs before being hunted by a cat, passing on the infection. Different worms use different animals as intermediate hosts.

Tapeworm is transmitted to cats and dogs via fleas. Infection occurs when a cat or dog ingests a flea that is carrying tapeworm eggs, for example while grooming. Flea ingestion is the only way in which tapeworm can be transmitted to cats and dogs.

Through Their Mother

Roundworm and hookworm can both be passed onto kittens and puppies through their mother.

Roundworm can penetrate the womb, passing from mother to unborn puppy or kitten.

They can also be transmitted to puppies and kittens via their mother’s milk. When a female cat or dog is infected with roundworm, some of the larvae remain dormant in the body until the pet becomes pregnant, at which point the larvae migrate to the mammary glands. They are then excreted in the mother’s milk when she feeds her young. This is a very common route of infection for roundworm.

Symptoms of Worms in Dogs and Cats

Cats and dogs infected with intestinal worms don’t always show any symptoms, which makes it difficult to spot. This is why prevention is so important.

However, they may sometimes show a few of the following symptoms of intestinal worms:

  • Diarrhoea (sometimes with blood)
  • Weight loss
  • Increased appetite
  • Itchy bottom
  • Vomiting
  • Pot-belly (in kittens and puppies)
  • Poor growth (in kittens and puppies)
  • Nutritional deficiencies and overall weakness
  • Tapeworm can appear like grains of rice around your pet’s bottom, in their bed or in their faeces
  • Roundworm and hookworm infections can result in a cough

As parasites, intestinal worms feed off the nutrients inside your pet’s body as they digest them. This means your pet will become weaker over time, and less able to overcome common, otherwise less serious illnesses.

In very severe cases, untreated worm infections can lead to fatalities in cats and dogs.

How to Prevent Worms in Cats and Dogs

Since it’s often difficult to spot a worm infection in your pet, it’s very important to administer regular worming treatment to prevent your pet getting infected in the first place. After all, prevention is always better than cure.

You should regularly give your pet a worming treatment specifically formulated for their species, size and weight – never give dog treatment to a cat and vice versa.

One treatment may not cover all types of potential worm infections, so you should speak to your vet about which types your pet is most at risk of catching to determine which treatment is most suitable for your pet. Other factors, such as whether your cat or dog is pregnant or has underlying health issues, will also impact which worming treatment is most suitable.

Worming treatment comes in a variety of forms, including tablets, spot-on solutions and liquid formulations. Here’s an introduction to some of the best worming treatments available.

Please note that these are not veterinary recommendations; for individual advice on the products that would work best for your pet, consult your vet.

Best Worming Tablets for Dogs

Prazitel Plus Worming Tablet for Dogs kills all four of the common intestinal worms in dogs, including roundworms, hookworms, whipworms and tapeworms. It has a tasty pork flavour and can be given with or without food.

Frontline Wormer Tablets for Dogs is suitable for dogs, including nursing dogs, and puppies from 2 weeks of age as long as they weigh at least 3kg. It kills roundworms, hookworms, whipworms and tapeworms. There is also a Frontline worming tablet suitable for larger dogs.

Beaphar WORMclear Worming Tablets are suitable for small and medium dogs and there is another version for large dogs – always give the dosage recommended on the pack for your dog’s size unless otherwise advised by your vet. These worming tablets for dogs contain pyrantel embonate, praziquantel and febantel, working quickly to kill all four types of intestinal worms that affect UK dogs and puppies over 2 weeks old.

Best Worming Tablets for Cats

Prazitel Worming Tablet for Cats is a meat-flavoured tablet that kills roundworm and tapeworm, the two types of intestinal worms that cats are most at risk of in the UK. It’s suitable for kittens over the age of 6 weeks and can be used for lactating cats.

Drontal Cat Worming Tablets kill roundworm and tapeworm, and can be used for cats and kittens over 6 weeks of age, as long as they weigh between 2-6kg. These fast-acting worming tablets are easy for cats to swallow and can be used during lactation but not during pregnancy.

Frontline Wormer Tablets for Cats are film-coated, meat-flavoured pills that kill both roundworms and tapeworms in cats. They can be given with food or on their own and are suitable for cats and kittens from 6 weeks of age who weigh at least 1kg, as well as nursing cats.

Read our blog, How to Give a Cat a Pill for advice on how to successfully administer tablets to cats.

Best Spot-On Wormers

Dronspot Spot-on Wormer Solution for Cats is a great choice for cats who don’t like taking tablets. Available for small, medium and large cats, this product is simply applied to the back of your cat’s neck to effectively kill tapeworm and roundworm in cats over the age of 8 weeks.

Best Liquid Wormers

Drontal Oral Worming Suspension for Puppies is intended to be given to puppies at regular intervals from the age of 2 weeks old until weaning. It comes as an easy-to-use liquid with a syringe for accurate dosing, and will protect puppies against roundworm, whipworm and hookworm.

Best Granule Wormers

Beaphar Worming Granules for Cats and Kittens are odourless and tasteless, and can be added to your cat’s food without them detecting it, making it a great choice for cats who resist tablets. It effectively treats roundworm infestations in cats over the age of 12 weeks.

How Often Should I Worm My Dog or Cat?

Always check the product instructions for your particular worming treatment, as the frequency of administration may differ from product to product. In general though, cats and dogs should be wormed every three months.

Some cats and dogs may need to be treated more frequently than this, as often as once a month. This is the case if:

  • Your pet is less than 6 months old
  • Your cat goes outside on their own or your dog goes on off-lead walks
  • You feed your pet a raw diet
  • Your pet lives with children, elderly people, or immunocompromised people

Find more advice on how often you should be worming your cat or dog here.

How Else Can I Protect My Pet from Worms?

As well as giving your cat or dog regular worming treatment, you should also:

  • Regularly disinfect your pet’s food and water bowls, especially if they have been left outside. Be sure to use a pet-friendly disinfectant
  • Regularly wash any soft furnishings that your pet has access to at 60°C

Can Humans Catch Worms from Dogs and Cats?

Yes, it is possible for some worms to be transmitted to us via our pets. However, it is not very common. It can occur in young children if they have been playing in areas where a cat or dog has been to the toilet. For more information on how intestinal worms can impact humans, visit the NHS website.

To help protect yourself and family members, wash your hands thoroughly with hot water and soap after touching your pet.

Wrapping Up

Regular worming treatment is essential to protecting your pet from the four main intestinal worms found in the UK. Tapeworm, whipworm, hookworm and roundworm are all unpleasant parasites which don’t always cause obvious symptoms in your pet. You can find a range of worm treatments on our website. Always consult your vet first before you start treatment. You may also wish to speak to your vet about the possibility of prescription-only wormers.

As well as intestinal worms, cats and dogs in the UK are also at risk of lungworm. Our pets can contract lungworm by accidentally ingesting larvae in infected slugs and snails, which then hatch inside the body. For more information about lungworm, which can be fatal, take a look at our blog.

Biography of Animed vet, Karin Volker, MRCVS