Didylidium caninum is the most common tapeworm for dogs. The adult worm, which can be up to 8 inches long, lives in your dog's small intestine. The worm has a mouthpart with six rows of teeth that attach to the intestinal wall, a neck and lots of tail segments. Fortunately, Didylidium caninum is easily diagnosed if you know what to look for, and modern treatments are safe and effective.
The Dog and the Worm
Inside the dog, tapeworm segments, called proglottids, grow from each worm's neck. Each segment has its own reproductive system, with male and female organs that enable a single worm in your dog to reproduce. As new segments are produced, the older ones are pushed towards the tip of the worm's tail, where segments contain about 12 fertilized eggs. End segments fall off and are passed in the dog's feces. The fertilized eggs are released as the segments dry and break.
The Flea's Role
Fleas act as intermediate hosts for Dipylidium caninum. Flea larvae will eat some of the eggs, and the tapeworms and fleas develop together. When the fleas are adults, the tapeworms are mature, too, ready to infect a dog. Your pooch can accidentally swallow the infected fleas when he chews or licks himself. The young tapeworms release in the dog's small intestine when the fleas are digested. These immature worms attach to their new hosts, and the life cycle begins again. After your dog swallows infected fleas, it will be about three weeks before you're likely to notice segments in his stool.
Signs of Tapeworm Infection
In an adult dog, tapeworms are unlikely to cause major health problems. The nutrients passing through the dog's intestine can usually feed the pooch as well as a light infestation of tapeworms, which don't need a lot of nutrients. A dog typically has few symptoms; your pooch may not have any. You might notice him scooting -- dragging his bottom along the ground -- or excessively licking his bottom if the segments passed in his feces cause irritation. Occasionally, a tapeworm detaches from the dog's intestinal wall and the whole worm passes in his feces or is vomited up.
Heavy Tapeworm Infections
A heavy tapeworm infection can be serious for a puppy and interfere with his growth. The pup may become anemic, and the worms could create an intestinal blockage. Even in an adult dog, a lot of worms can cause vomiting, diarrhea and weight loss. Tapeworms are generally detected before they become a problem, because you'll likely notice them in his stool or crawling in the fur around his rear end. The segments look like white rice grains, about an eighth-inch long, and they turn a golden color when they dry out.
A Double Treatment
A single treatment with a medication such as praziquantel, given in tablet form or by injection, will kill all the tapeworms in your dog's body. The worms dissolve in the dog's intestine and normally won't be seen in his stools. Your veterinarian may recommend a second dose of wormer three weeks after the first treatment, as any dog infected with Dipylidium caninum will also need to be treated for fleas. Getting fleas under control can take up to a month. All the dogs in your home, and cats, as they have the same fleas, will need treating.
Dipylidium Caninum and People
You can't get tapeworms directly from your dog, but Dipylidium caninum can infect a person who accidentally ingests a flea. Children occasionally swallow infected fleas while playing with dogs. See your physician for a diagnosis and treatment if you think your child may have contracted tapeworms -- segments can be seen in bowel movements.