These are a common problem, Lets look at the types of worms your dog may encounter, and what ill effects they can cause.

The most common types in the UK are Tapeworms and Roundworms of course in warmer climates differing species are encountered.

If you would like to contact me regarding other types of worms encountered I will be pleased to add the information but for now I will concentrate on the main ones encountered in the UK.

Roundworms

Roundworms (Toxicaria canis, Toxicaria cati, and Toxascaris leonina) are common parasites found in both dogs and cats. These are by far the most common intestinal parasite of puppies and are normally acquired prior to birth via the mother's bloodstream. Roundworms can also be transmitted via the milk whilst the puppies are nursing. Roundworms lay many thousands of eggs which can easily re-infect your pet if the surroundings are not kept clean and free from facaes. Adult roundworms live in the small intestine and in puppies and kittens roundworms are often referred to as ascarids. The roundworm is the most common form and these are found worldwide.

Symptoms of roundworms

The main symptoms include potbelly - diarrhea - gas - vomiting - lack of energy - slower growth rate - and dull coat. If the immature roundworms are migrating through the lungs then coughing can also occur. Some dogs can show all these symptoms, some a few and some none at all.

How does my dog get roundworms?

 they are transmitted in one of four ways, Eggs are passed in the stool "baby roundworms" if these are taken in by the mouth (ingested) the eggs are infectious. Roundworms can be carried by an intermediate host such as birds, beetles, earthworms and mice. The puppies can be infected in the womb. Infectious larvae in the mother's system pass across the placenta and infect the growing puppies. The larvae can also be secreted and deposited in the Mothers milk which is then fed to the puppies infesting them.

Roundworms and humans

Although extremely rare roundworms can affect humans, resulting in a condition called Visceral Larva Migrans. The roundworm larvae migrate around in the tissue of a person's abdominal organs, causing damage to the organs which can sometimes be severe and even fatal. Humans are not the definitive host and roundworms will not develop into adult worms in them. People most at risk of developing Visceral Larva Migrans are children, especially if they have been eating dirt. This condition can be prevented by careful attention to hygiene, make sure all pets are checked and treated routinely for roundworms and other parasites your veterinarian will be able to prescribe the best medication and will indicate how often the treatment should be repeated , don't let children eat dirt or play with the stools of pets.

Tapeworms  
(Diplidium caninum, Taenia pisiformis and Taenia taeniaformis) are common parasites found in both cats and dogs. Tapeworms live in the small intestine and compete with the pet for the food they eat. These are the worms that are usually responsible for your pet having an itchy back end. The worm lives in the intestine and can be up to twenty inches long. Tapeworms are composed of segments and these are passed out through the pets anus. They can often be seen sticking to the coat under the tail and they look like dried grains of rice. The most common source of tapeworm infection is the flea, so tapeworms are very common in summer and Autumn

Symptoms of Tapeworms

The most common symptom is your dog rubbing his/her rear end along the floor to relieve the itching caused by the crawling egg which contains segments shed by the worm, in some cases the coat will be dull and your dog may show weight loss, they can also experience diarrhea, vomiting, excess gas and a lack of energy. In severe cases the tapeworms can cause an intestinal blockage due to their bulk, however in most cases the tapeworms cause little impairment to the health of your dog.

How does my dog get Tapeworms?

Tapeworms are transmitted when the pet eats an intermediate host containing the infectious stage of the tapeworm. Creatures that act as intermediate hosts include fleas, mice, rabbits, and many small insects. Tapeworms can also be transmitted by raw or poorly cooked pork, fish or beef. Once the infectious stage is eaten the tapeworm embeds its head into the wall of the small intestine, it then forms a long segmented body. The end segments (proglotids) are the oldest ones and they contain the infectious egg of the tapeworm, these segments will periodically break off and crawl around on the pet's rear end or will exit in the stool. After leaving the body the tapeworm segment dries and is eaten by one of the intermediate hosts as above and the cycle begins again.

Tapeworms and humans

 Generally speaking the answer is humans can't catch dog or cat tapeworms although it is possible under certain bizzare circumstances. If proper hygiene is observed humans will not become infected. It should be noted at this point that humans can get infected on occasion with other species of tapeworms but not from dog or cat tapeworms. Humans usually get tapeworms from eating poorly cooked meat products.
Once treatment has been given the tapeworms are eliminated as they have a direct life cycle. Though re-infection is not uncommon. Try to keep your pet free from fleas, do not feed raw or undercooked meat or fish, and try to minimise hunting for things such as rabbits and mice. Again your veterinarian can prescribe a very effective treatment for this problem, follow the instructions and repeat as often as instructed

Tips

Always clean up after your pet make sure that puppies and young dogs do not eat their own stools or the stools of others. If you have more than one pet it is wise to treat them all at the same time (your veterinarian will advise on this) to prevent cross infection.

 Remember to always wash your hands after dealing with excrement or after handling young dogs or puppies.