factsheet – fleas and worms

Fleas and worms
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What are fleas?
Fleas are known as external parasites. An external parasite is an organism that lives and feeds on the surface of another animal. Fleas are small, brown, wingless insects with a flattened appearance that allows them to move freely through a cat’s fur. Fleas have a specialised mouth that pierces the skin of the cat and sucks on the blood. Flea saliva contains anti-coagulants that stop the cat’s blood from clotting.

The flea, once on your cat, will stay and lay eggs. One female flea can lay around twenty eggs per day. Flea eggs do not stick to the animal’s coat so will be shed throughout the environment. This means anywhere your cat grooms themselves, sleeps, or is patted.

The eggs can be found on clothes, bedding, and furniture. Depending on the environment, a flea egg will hatch within 2-7 days. When the egg hatches, small ‘maggot’ type larvae appear. At first they are white in colour, but then change to brown as they develop into a flea. The larvae feed on dead skin cells, flea fæces , and sometimes tapeworm eggs. Flea larvae are light sensitive and tend to live in dark areas like deep carpet layers and underneath furniture. The flea larvae can become adult fleas within a few months. Fleas can live on both cats and dogs but cannot live on humans. They will often bite humans, but cannot survive on their blood.

It is important to note that fleas can be living in grass so even if your cat doesn’t go outside, they may still get fleas. Fleas and flea eggs can travel in the wind, through open windows and even on our clothes.

If you have a very young kitten or elderly cat, always chat with your vet about what the best treatment for fleas and worms will be for them.

How to recognise if your cat has fleas
Once fleas are established in your home they may cause itching and irritation in your pets, and they can often bite humans. Some people and animals have an allergic reaction to flea saliva, causing severe irritation at the bite site. An individual cat may tolerate a small number of fleas; others may develop an allergic reaction to the same number. Signs to look for in your cat that show flea activity include:

  • Over-grooming
  • Scratching
  • Hair loss
  • Small black flecks, known as flea dirt, in the fur
  • Pale gums
  • Ulcers on the lips or mouth

Hazards for your cat if you don’t treat fleas
There are a number of reasons you need to treat your cat for fleas. Firstly, flea bites will cause your cat discomfort. When your cat is scratching they are trying to relieve this irritation. Some cats can be very allergic to flea bites causing severe dermatitis, hair loss, and over-grooming. Secondly, fleas are feeding on your cat’s blood. This can cause severe blood loss or anaemia in your cat, and in the case of small kittens or older cats, can kill them. Lastly, as flea larvae can feed on tapeworm eggs, this can make the flea a host for tapeworm. The flea can pass the tapeworm on to your cat, or you.

Treatment for fleas is as easy as a spot of liquid on the back of the cat’s neck once a month. We recommend ‘Advantage’ for fleas or ‘Advocate’ for fleas and worms. You will need to make sure the environment the cat lives in is treated as well to kill any larvae or eggs that may be around. Vacuum regularly to avoid the eggs hatching. If your cat has sensitive skin, you can also get an oral flea treatment, ‘Comfortis’, that can be placed in their food or directly into their mouth.

What are worms?
The worms your cat can have are intestinal worms. These worms are known as internal parasites as they live and feed inside a host. Tapeworm, roundworm, and hookworm are the types that can live inside your cat.

Worms live in the intestines and feed on the nutrients from the food your cat consumes. Hookworms feed on damaged tissue in your cat’s stomach and intestines. Hookworm and roundworm can be passed on by ingestion of the worm eggs from the environment, usually grass. Tapeworm is passed in the fæces and can stick to the fur, thereby passing on to the grass or bedding. Tapeworm can also be transmitted by fleas, as well as in a mother cat’s milk to her kittens.

How to recognise if your cat has worms
It is not always possible to tell whether your cat has intestinal worms. There are a few signs you can look for to see if your cat has worms. These include:

  • Overeating with no weight gain
  • Irritation and constant licking of the anus
  • Bloating of the stomach
  • Rubbing of the anus on the ground
  • Worms (alive or dead) in your cat’s fæces
  • Pale gums
  • Small worm segments – tapeworm – in the fæces or in the the cat’s fur around the anus

Hazards for your cat if you don’t treat worms
As worms feed on the nutrients from your cat’s food, or worse, your cat’s intestinal tissue, this can mean your cat isn’t receiving all the nutrients they need to survive (this is why cats with worms do not put on weight). Severe worm infestations can cause long term gut irritations and can even kill very young kittens and elderly cats. It is also important to treat your cat for worms to stop the possible transmitting of worms to other pets or humans.


Worming your cat is a very simple procedure. We recommend a spot-on treatment once a month, ‘Advocate’ to treat worms and fleas (please note your cat will still require a treatment every three months for tapeworm if you use ‘Advocate’), ‘Profender’ spot-on treatment for all intestinal worms or ‘Milbemax’ oral treatment, every three months for intestinal worms. Please note you may see dead worms in your cat’s fæces after using a worming product. This is normal as the dead worms are being passed from the gut.

If you suspect you may have contracted worms from your pet this is also very easily treated; see your doctor or pharmacist for advice.

While all care has been taken in preparing this document, it is intended to provide general information only and should not be taken as constituting professional advice. Mention of a product or business does not mean endorsement by Cat Protection.