Tapeworms live in the intestines of their carnivore hosts. If your dog has tapeworms you may see the tapeworm segments around the tail or anal area. They look a little bit like grains of rice. They are white to yellowish in colour and may wriggle and move. After they have been shed they will eventually dry and shrivel up. Sometimes if your dog has a very heavy infestation of tapeworms then it may show signs of weight loss or general malaise. Occasionally these worms may cause vomiting or diarrhoea; large segments of the tapeworm could be vomited up. Dogs with tapeworms may also show signs of anal irritation since the tapeworm segments can cause itchiness and irritation as they emerge. The dog with tapeworms will therefore groom and nibble around its tail and bottom quite frequently.
The tapeworm which is most common in both dogs and cats is called Dipylidium caninum. It lives in the small intestine and regularly sheds segments which are about 5-8mm long. These segments are passed from the anus of the dog and may be noticed around the tail area. The segments will usually fall from the dog eventually and they will then shed their eggs into the carpet or cracks in the floorboards where flea larvae will become infected. When the infected flea larvae (which is the intermediate host) develops into an adult flea it will find a host such as a dog to complete its own life-cycle. Since the infected flea is likely to irritate the dog and be eaten during normal grooming activities the worm will be passed on to its final host - your dog! The life-cycle of this worm takes about three weeks so it is roughly in line with the length of its intermediate host's life-cycle. If your dog has a flea problem then it will almost certainly have these tapeworms too! If you want to get rid of these worms you must control the fleas. See the article on fleas for advice.
Dogs may catch the tapeworms Taenia ovis, T. multiceps, T. serialis T.hydatigena and Taenia pisiformis by eating sheep carcases or small prey mammals such as rabbits. If your dog is a hunter then it is likely to be infected with these tapeworms from time to time. Exposure to these worms is dependent upon your dog's lifestyle. Indoor type dogs may never catch these tapeworms while regular outdoor rabbiters may be frequently infected. The segments of these tapeworms are often noticed since they can be about 1 cm in length.
The most worrying of the tapeworms which may infect your dog in the UK is Echinococcus granulosa. This tapeworm is small so it would probably not be noticed in the same way that other species would be. The life cycle of this parasite is around 5 weeks and it is a problem because it can infect humans as well as other animals. Humans together with pigs, sheep, cattle and deer are intermediate hosts for this tapeworm. The final hosts include cats and dogs as well as some wild carnivores. It is a problem for humans because in the intermediate hosts these worms form cysts (called hydatid cysts) these cysts are formed in vital organs such as the liver or lungs and can cause organ failure and even death. In rural areas, especially where sheep are present these worms may be a particular problem since the dogs may eat parts of infected sheep carcasses and catch these parasites. It is very important that owners of dogs are aware of this zoonotic disease and treat their dogs for worms regularly. This is particularly important if your dog hunts, scavenges or receives any raw meat as part of its diet. In the UK this problem is not as widespread as in Europe where the tapeworm Echinococcus multilocularis is a more serious problem.
Dogs should ideally be treated for worms every three months with a reliable product such as Drontal. If your dog is a regular scavenger/ hunter or has fleas then it may be necessary to worm him more frequently.