Within the UK
Roundworms (Toxocara):
White worms that look like a piece of string or spaghetti. Present in puppies from 2 weeks old and kittens from 6 weeks old as they can become infected from their mother in the uterus and via their milk. In young animals they can cause lethargy, bloating, diarrhoea and weight loss. These worms can be transmitted to humans and although a rare ocurrence, in children they can cause permanent eye damage leading to blindness, so for this reason alone all pets should be routinely treated for roundworms.
Tapeworms:
These worms attach themselves to the small bowel and can grow up to 5 meters long! They look like flat ribbon shaped pieces or pale segments the size of a grain of rice which can often be seen in your pet’s fur or around the anus. Often pets become infected by swallowing fleas when grooming which carry the tapeworm larvae. Dogs and cats that hunt can also be infected from their prey. Dogs that holiday in Wales and Scotland can also be at risk of the sheep tapeworm, which can also be transmitted to humans.
Hookworms:
Hookworms are blood sucking parasites that live in the small intestines. More commonly seen in kennelled dogs, leading to diarrhoea and even anaemia. Hookworm larvae can directly penetrate your pet’s feet leading to infection. Hookworms can cause human skin disease.
Whipworms:
Whipworms are blood sucking parasites that live in the large intestines. They can cause diarrhoea and anaemia similar to hookworms. More common in kennelled dogs. Faeces of infected dogs will often be mucous covered.
Lungworms:
Infection occurs when dogs eat infected snails or slugs or possibly lick the mucus trails. Foxes are the main host. Does your garden attract urban foxes? The associated symptoms in dogs are coughing and respiratory problems.
Outside the UK
As well as the types mentioned above, travelling pets may come into contact with worms only found abroad:
Heartworm:
Heartworm gets its name as the adult worms will live in your dog's heart. Spread by infected mosquitoes, causing coughing, and appetite loss with advances stages being fatal. These worms are only found in Southern Europe, USA, and Australia.
Tapeworm - Echinococcis multilocularis:
Does not occur in the UK. This worm can infect your pet but can also cause very serious liver disease in humans.