Dog - Tapeworms

What are tapeworms?

Tapeworms, as their name implies, are flattened intestinal worms. They consist of many small segments each approximately 3–4 mm long. Unlike roundworms which live freely in the bowel, tapeworms attach to the wall of the intestine with special hook-like mouthparts.

The most common tapeworm of dogs (and cats) is Dipylidium caninum. Adult worms reach approximately 20 cm (8") in length. The individual segments are developed from the anterior (front) end. They gradually mature, finally being shed from the rear of the tapeworm, either singly or in short chains. The segments are passed out on the faeces when the dog defecates. 3 mm (1/8") in length, they resemble grains of rice. Occasionally they can be seen moving on the hairs around the anus or on freshly passed faeces. These mature segments are packed with fertilised eggs. As they dry they become gold coloured and split to release the eggs.

Unlike roundworms dogs cannot be infected by eating these tapeworm eggs. They have to pass through an intermediate host which in the case of Dipylidium caninum is most commonly a flea.

How are dogs infected?

When the fertilised eggs are released into the environment they have to be ingested by flea larvae (immature fleas). Inside the flea larvae the eggs develop as the larvae develop and ultimately become fully infective in the adult flea. During natural grooming or nibbling to allay irritation the dog ingests the flea which is digested and the infective tapeworm larvae completes its development in the intestine of the dog.

Are tapeworms dangerous for my dog?

Tapeworms do not usually cause too many problems in adult dogs. It is usually the appearance of motile segments crawling round the anus that causes owner concern. Occasionally dogs will be seen dragging their bottoms across the ground (scooting). This is done to relieve the irritation. This behaviour however can also be due to other reasons, e.g. impacted anal sacs.

In puppies tapeworm infestation can be more serious. Lack of growth, anaemia and sometimes blockage of the bowel can occur depending on the number of tapeworms involved. Sometimes contact with the bowel wall is lost by the scolex (head of the tapeworm). The entire worm is usually then passed either in the faeces or is vomited.

How is diagnosis made?

Initial diagnosis is usually based on the history of 'rice grain segments moving around the dog’s anus'. Sometimes yellowish dried segments are found in the dog’s bed.

Tapeworm segments are only passed intermittently and therefore are often not diagnosed on routine faecal examination. If you do find any segments, white or yellow in colour, please let us see them so we can make a definitive diagnosis.

What is the treatment?

With modern drugs, treatment is simple and very effective. Worm treatment is available in the form of tablets, injection or as a spot-on preparation (which also covers roundworms, fleas and other ectoparasites).

These drugs are very safe and should not cause vomiting, diarrhoea or any other adverse side effects. However the majority do dissolve the worms so that a mass of dead worms following successful treatment is now largely a thing of the past.

Is there anything else I should do?

Control of fleas is vital in the management and prevention of tapeworm infection. Flea control involves treatment of the dog, and the environment. A separate fact sheet is available which we will be happy to supply.

In a flea infested environment your dog can become reinfected with tapeworm in as little as two weeks. Since tapeworm medication is effective, return of tapeworms is almost always due to reinfection from the intermediate host and not due to failure of the product.

Can we catch canine tapeworms?

Human infection is not common or likely. Direct infection from the dog is not possible and thus human infection with Dipylidium caninum would depend on the victim swallowing an infected flea. A few cases have been reported in children. Even this very slight risk can be eliminated with vigorous flea eradication.

Are there any other canine cestodes (tapeworms) that could pose a problem?

Yes, some other tapeworms are important:

1. Taenia species. These tapeworms are acquired by the dog when eating prey or offal containing the infective larval stage. These are very much larger tapeworms, often up to one metre (over 3 ft) in length. The intermediate stages develop 'hyadatid cysts' in various organs. Very efficient anthelmintic preparations are available.
2. Echinococcus species. These are very small tapeworms. They consist of only three or four segments and are usually less than 1 cm (3/8") in length. Intermediate hosts can be sheep, horses or occasionally man. Infection is by ingesting eggs originating from the faeces of dogs or foxes harbouring the adult tapeworm. In the UK Echinococcus problems are localised to mainly sheep grazing areas. In parts of Europe and North American Echinococcus can pose a major public health problem. Fortunately de-worming preparations, particularly those containing praziquantel are very effective for eliminating these cestodes from the dog.

Such treatment is now mandatory for any dogs entering or re-entering Britain from abroad under the Pets Travel Scheme (PETS).  See PETS handout.

Control measures involve avoidance of uncooked or partially cooked meat and offal.

If you would like to discuss any of these matters further, do not hesitate to contact us.