Q. How did my dog get tapeworms?

Leslie Sinclair, DVM says: Tapeworm larvae are carried by fleas, so dogs usually become infected with tapeworms when they ingest a flea. The adult tapeworm is made up of many segments, called proglottids, each about the size of a grain of rice (adult tapeworms can be as long as 8 inches). As a tapeworm matures inside the intestines, these proglottids break off and pass into the stool. They are able to crawl, and they can usually be seen in a dogs stool or crawling about near the dogs anus. The segments eventually dry up and break open, releasing tiny tapeworm eggs onto the ground. These eggs are then ingested by flea larvae, and the cycle starts over again.

As disgusting as they may seem, tapeworms cause little harm to dogs. Sometimes a dog will find their movements irritating and will scoot, that is drag his anus across the ground or carpet to relieve the discomfort. Rarely, a very long tapeworm in a dogs intestines will extend into the stomach and cause the dog to vomit. Puppies who are infested with tapeworms may develop severe diarrhea or vomiting that may lead to dehydration, a potentially fatal condition.

Veterinarians typically give treatment when the tapeworm segments are observed or when a dogs scooting or vomiting cannot be attributed to any other cause. The drug praziquantel is the most common treatment and causes few side effects. It eliminates Dipylidium caninum, the most common canine tapeworm, as well as the tapeworm Taenia pisiformis, which dogs can get when they eat the viscera of rabbits and rodents. There are other, rare species of tapeworms that infest dogs, and there are other tapeworms that affect humans but not dogs.

While humans cannot be infected by Taenia pisiformis, people, especially children, can become infected with Dipylidium caninum by accidentally swallowing a flea, although the risk of this is minimal. The most effective way for dogs and humans to prevent infection is to practice effective flea control.

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