When Did You Last Worm Your Cat or Dog?

Most pet owners know that cats and dogs can become infected with worms and the concept of a regular worming programme is well established, but how many people really know why their pet needs worming, which product they should be using and how often it should be done?

Worming Programme

A worming programme should be tailored to suit each individual animal and its circumstances and in order to do this we must consider which worms our pet is most likely to harbour:

Ascarids or Round worms

Ascarids or Round worms commonly affect young animals. Puppies and kittens usually become infected before birth via the placenta, and also in the first few weeks of life by larvae which pass in the mother’s milk. Larvae develop into adult worms and live in the young animals gut, producing several thousand eggs per gram of faeces. Infected animals become stunted and ‘pot-bellied’, may vomit and have diarrhoea and in some instances can lead to a total intestinal blockage. The eggs which are passed in the faeces develop into larvae and are very resistant to damage and can remain in the environment for up to 2 years. Larvae that are accidentally eaten by other animals (this can include humans!) migrate from the intestine entering a resting state in other tissues such as muscle. Usually larvae migrate without causing any signs of illness to the host, but in some cases the larvae can come to rest in the eye or cause damage to organs which the larvae have migrated through.

Tapeworms or Cestodes

Tapeworms or Cestodes generally cause limited harmful effects to cats and dogs, but the sight of a tape worm segment is quite alarming and repulsive to most people! Cats and dogs become infected by eating raw meat, offal, prey species such as rabbits, rats and mice and also via fleas and lice. Tapeworms are more of a problem to other species because when eggs are accidentally ingested, they pass via the blood stream to various parts of the body and produce cysts. If a sheep ingests tapeworm eggs from dog faeces, cysts sometimes develop in the brain and causes the disease known as ‘gid’ which leads to impaired vision, circling, head pressing and eventually death. The only cure is surgical removal of the cyst. Immature stages of tapeworm can also affect humans by causing cysts in the lungs and liver.


Hookworms are not common in the UK but are most likely to occur in breeding, greyhound or hunt kennels, especially if they are allowed access to permanent grass runs. The larvae penetrate the skin causing dermatitis especially of the feet.


Whipworms burrow into the large intestine, and if present in numbers can cause bloody, mucus diarrhoea. Clinical signs are rare in the UK but again are more likely to occur if dogs have access to a permanent grass run.


Lungworms. Dogs acquire lungworm infection by eating slugs or snails. It is quite rare but causes coughing and exercise intolerance. In cats it sometimes causes coughing, but low-level infections often go un-noticed


Anthelmintic is the name given for a drug which acts against worms. Some only treat round worms or tapeworms whilst others cover both. They come in various preparations including tablets, liquids and granules, or spot-on for ease of application.

It is good practice to weigh the animal in order to be able to administer an accurate dose.

How Often?

If a cat or dog is neutered, does not hunt or eat raw meat and is treated regularly for fleas then the minimal treatment it requires is a round wormer every three months.

On the other hand if a cat or dog hunts, has access to raw meat or may have fleas or lice, it is advisable to use a wormer that covers both tapeworms and roundworms, and in high risk cases as often as once a month.

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