You saw those rice-like bits around your pup's backside, the telltale signs of tapeworm infection. Tapeworm segments aren't contagious to children; the only way they can catch a dog's tapeworm is by eating an infected flea.
Tapeworm: A Life
Tapeworm is an intestinal parasite, reaching 6 inches or more in length, that attaches itself to your dog's small intestine. The tapeworm is a head, that holds onto the intestinal wall, a neck and individual segments, or sacs, each with its own digestive system and reproductive tract. As the worm matures, the segments move down the "chain," dropping off the tail and leaving through your dog's rectum. You may see these segments in his poop, or spot them in his bed. The sac may move, since it's filled with tapeworm eggs, and eventually, it will dry up, releasing the eggs.
Enter the Flea
Dipylidium caninum is the most common type of tapeworm in dogs, and its released eggs aren't infectious to animals or people. In fact, without a flea, this brand of tapeworm can't infect anything else because it relies on fleas to perpetuate its life cycle. Flea larvae ingest the eggs while they feed on dirt, dandruff and dust, unwittingly becoming a vector for tapeworm. When your dog grooms himself and swallows an infected flea, the parasite enters your dog's intestinal tract to begin the process again. So, unless your child unknowingly eats an infected flea, he's safe from getting this kind of tapeworm.
Other Tapeworms, Other Hosts
If your dog likes to hunt prey in your yard, it's possible he can pick up a different variety of tapeworm from an infected rodent, such as a squirrel or rabbit. The Echinococcus and Taenia species of tapeworm use large animals, such as deer, and rodents, such as mice and rats, as intermediate hosts. Humans get Taenia infections by eating infected meat, such as pork or beef. Echinococcus can be passed and transmitted through a dog's stool, but it's very rare in North America.
Even though you or your children can't pick up tapeworm from a segment, it's still best to treat your dog to get rid of these parasites. Your vet can prescribe medicine, such as praziquantel, to kill the tapeworm. Preventing fleas is key to keeping tapeworm at bay since these parasites rely on fleas to keep the cycle going.