Why Is It Important to Treat Puppies and Kittens for Worms?

Why do puppies and kitten need worming throughout the year?

Created: 8/9/2021 Updated: 1/19/2024 - Vicky Payne

Health & Wellbeing

Pregnant cats and dogs can pass roundworms (Toxacara) to their offspring through the placenta before the puppies or kittens are even born. Further infection can then take place through the milk, grooming, and from the mother’s coat. Pregnancy hormones stimulate roundworms (which have been encysted in body tissues) to migrate.

Larvae present in the puppy or kitten at birth will develop into adult worms by the time the puppy or kitten is two weeks old. Roundworms can cause abdominal pain, diarrhoea, stunted growth, and a pot-bellied appearance. Puppies and kittens may not pass worms in their faeces, even with a heavy infestation.

A severe roundworm infection can be debilitating, and sometimes fatal, for a young animal. Added to the risk for the pet, infected puppies and kittens can shed eggs into the environment which can infect children. Toxacara can cause serious health conditions in children including blindness and liver damage.

Common types of worms


There are two species of roundworm affecting cats and dogs: Toxacara canis and Toxascaris leonina. They grow into long spaghetti-like worms which absorb nutrients from the puppy or kitten. Roundworms can hide in body tissues (encyst) which can make them difficult to completely eradicate.


Tapeworms live in the small intestine and absorb nutrients from food as it is digested. They have a row of sharp teeth which grip onto the gut wall and can grow to over 15cm in length! Tapeworms reproduce by shedding segments which pass out in the faeces. These segments look like rice grains and are sometimes seen in pets’ fur.


These are short blood sucking worms which can be fatal to puppies and kittens. They are less common in the UK than in Europe.


Again, a less common worm in the UK. These live in the large intestine and are less likely to cause health problems.


Contracted from the infected slime of slugs and snails, lungworm is a problem for dogs in the UK. It can cause persistent coughing but can also cause fatal bleeding disorders.

Black and brown puppy dog sat on grass

Signs your puppy or kitten has worms

Assume that your new puppy or kitten comes with worms! There may be no signs of worm infection if your puppy or kitten has a light infection.

Heavier infections may cause diarrhoea, poor weight gain, a poor coat, lethargy, and a pot-bellied appearance. Advanced cases can cause constipation by blocking the gut. In some cases, puppies and kitten will vomit roundworms or pass them in the faeces.

How to prevent worms in puppies and kittens

When rehoming a puppy or kitten, you should ask to see records of the worming that the breeder or rescue organisation has carried out. It is usual for at least two courses of worming medication to be given before a puppy or kitten is 8 weeks old. The following product is suitable for use in puppies and kittens from 2 weeks of age:

When you take your puppy or kitten for their first health check and vaccination, your vet will be able to advise on an ongoing worming schedule. Most will advise monthly roundworm treatment and tapeworm treatment every 3 months. The following products are suitable for puppies and kittens in their new homes:

Black and white kitten with mouth open

If lungworm is a risk for dogs in your area you will need a prescription lungworm treatment from your vet. These should be given once a month.

Puppies and kittens usually come with a few fleas too, which are not only irritating but also spread tapeworm. Fleas can be infected with tapeworm eggs, which the puppy or kitten then ingests during grooming. Clever, but gross!

Keep your new puppy or kitten flea free with some of the following products:

For home infestations the following products can be useful, but follow the guidelines for safe use carefully:

Close up of puppy looking at camera

Clean up after your pet

Even if your pet is regularly wormed, it remains the responsible thing to do to clean up after them. Puppy owners should always take poop bags with them and dispose of dog waste in a bin. Kitten owners should encourage their pets to use indoor or outdoor litter trays to reduce the risk of contaminating garden soil, especially with the popularity of home vegetable growing!

Interestingly, fresh pet faeces have a very low risk of causing infection in humans, with the eggs of some species only becoming infective after as long as a month outside the body. Even so, washing your hands (or using a hand sanitizer gel if out and about) is highly recommended.

Do you need further advice?

If you need any further advice, please contact the OSCAR Helpline Team on our freephone number 0800 195 8000 or email helpline@oscars.co.uk.