Worming Your Dog


There are two main types of intestinal worms that affect the dog and cat; Cestodes (Tapeworms) and Nematodes (Roundworms).

If a pet has a lot of intestinal worms (a high worm burden) they may have symptoms such as a potbelly, vomiting, diarrhoea, lethargy, a dull coat and sometimes an intestinal blockage can occur causing faecal constipation.


The tapeworm head attaches to the intestines and grows a chain of segments each of which contains eggs. As the segments fill and drop off they are passed in the faeces and may be found wriggling around the anus. The segments look like grains of rice and seeing them on the fur may be your first sign of a tapeworm infestation.

The tapeworm species Dipylidium canium is also carried as an egg cyst in every flea’s body so if a pet has fleas and accidentally swallows one when grooming itself then this becomes the start of a tapeworm cycle. Humans may also be infected with it if they accidently ingest a flea too, this is therefore, a zoonotic parasite.

Taenia species of tapeworm may be passed to dogs and cats who are fed raw meat or hunt rabbits and mice. Echinococcus granulosus is another type of tapeworm which may be caught when a sheep carcass is eaten. Therefore if your pet is out hunting, regular worming is advised and raw meat diets are best to be avoided.

Small mammals such as mice and rabbits play a part in some lifecycles of the tapeworm species, as already discussed. Mice, gerbils and hamsters may also be infected with a type of tapeworm and this is zoonotic to the owner if eggs are accidentally ingested. Faecal samples can be examined for eggs but light infections are well tolerated.


Roundworms look like spaghetti and are not segmented so are easy to distinguish from tapeworm. Roundworms can be broken down into Ascarids, Hookworms and Whipworms.

The Toxocara species (part of the ascarid group) may be transmitted from mother to infant through the umbilical cord and through the milk, from the environment or when eating rodents and birds which have picked them up from the environment themselves. Toxocara canis is responsible for interfering with vision when ingested by humans so definitely worth keeping your pet's worming up-to-date.

Roundworm infections are not usually a problem in the smaller mammals kept as pets although rats, hamsters, gerbils and mice can carry pinworm infections. A minor burden is usually tolerated although too many can cause diarrhoea, rectal prolapse and poor body and coat condition.


Hookworms such as Uncinaria stenocephala are found in high percentages throughout the fox population in the UK. Infected dogs are most likely to come from kennels or areas where a large number of canines are repeatedly exercised in the same grass runs. The larvae in the environment can penetrate the skin and cause a reaction (dermatitis). If ingested the larvae travel to the intestines and may cause diarrhoea.
Infection of this type of hookworm in cats is unlikely but is possible with Ancylostoma caninum, however it is unknown how commonly this occurs, as it is not widespread in the UK.


Whipworm (Trichuris vulpis) is again picked up from the environment when eggs are passed in the faeces of an infected dog. When the eggs are ingested the larvae goes through stages until it develops as an adult worm in the large intestine. Low level infections are well-tolerated and discovered by identifying eggs in a faecal sample however a heavy burden may result in severe diarrhoea and dehydration. It is a disease of dogs only.

Worm Treatments

The are a variety of wormers on the market but it is worth checking exactly which worms they kill, generally speaking it is worth selecting a broad spectrum wormer such as Drontal, Milbemax, Cestem, Cazitel or Plerion which are avalible in a palatable tablet form. Although Milbemax is only available with a writtten veterinary prescription, Drontal, Cestem, Cazitel and Plerion are both available without the need for a prescription. Drontal is available in Drontal Cat; dosing cats weighing up to 4kg, Drontal Cat XL; for cats over 4kg, Drontal Plus; each tablet dosing 10kg of body weight and Drontal Plus XL with each tablet dosing 35kg of bodyweight. It is extremely important to give the correct dosing, as under dosing is likely to be uneffective and may create resistance to future treatment. Plerion 5 tablets each dose 5kg of bodyweight and Plerion 10 tablets each dose 10kg of bodyweight. Cestem tablets are only available for dogs and each liver falvour tablet doses 10kg of bodyweight.  Cazitel is also only  available for dogs in a pork flavoured tablet, each dosing up to 10kg of bodyweight.

Examples of spot on wormers include Droncit, Profender and Stronghold.

Return to index