Devoted to More Wags and Purrs.
Continuing the "things you don't want to read with your breakfast" theme...

The Gross, but Interesting, Tapeworm

Tapeworms (Dipylidium caninum) are one of the most famous of pet parasites; primarily because they are one of the few intestinal worms that make their presence obvious. People often find tapeworm segments, which look like flattened grains of rice, in the litter box or dog bed, on their pet, or even crawling on themselves. While disgusting, one has to admire the complexity of such a “simple little worm.”

Tapeworms, like most intestinal worms, live their entire lives in the intestines, and will only leave if killed or forced out. The tapeworms themselves can be several inches long; the rice-like segments seen crawling out of a pet are not actual worms but mobile packets of eggs called proglottids. The proglottids are little armored personal carriers, moving these egg packets to the ground, where the eggs are released and the life cycle continues.

Once the tapeworm eggs manage to make it to the ground, their life cycle takes a complicated twist as an intermediate host is required, The egg packets have to be ingested by a flea larva, which are are the worm-like larva of recently hatched fleas that feed on debris an the ground. Once inside the flea, the tapeworms larva, now called an oncosphere, burrows through the flea’s intestinal wall and lives in the flea’s abdomen. The flea then grows up with this developing tapeworm, now called a cysticercoid, inside of it.  For the tapeworm to continue its life cycle, the flea now has to be eaten by a dog, cat or another mammal (including people!)

Tapeworms themselves, while disgusting, cause less problems than most other intestinal parasites. They do minimal damage to the walls of the intestine, and the amount of food they consume in negligible. In the late 1800’s, unscrupulous snake-oil salesman used to sell human tapeworm eggs in capsules as a “diet pill.” Apparently, while they did give people tapeworms, they did not help people lose weight. Some individual animals may have allergic type reactions to the worms, or if huge numbers are present they could actually cause an intestinal blockage. Some pets will also injure themselves licking and biting at themselves as they feel the worms crawling out.

There is another species of tapeworms, Echinococcus species, are luckily much less common in the United States, but have the potential to be dangerous. These worms will burrow through the intestines in mammals to form a cyst inside the abdomen. Hunters will sometimes find these cysts in deer or other hunted animals. These tapeworms can cause severe disease in humans if they are ingested.

Tapeworms are easily treatable by oral medication, though the medication which kills other intestinal parasites is often ineffective for tapeworms. Since tapeworms typically are caught by eating fleas, treating for fleas becomes important as well. Without getting rid of the source for the tapeworm infection, they can be re-caught the day after treatment.

Tapeworms, like so many parasites, can be really fascinating in their complexity. Unfortunately, this does not make them any less gross.
 

Michael J. Rumore, D.V.M.