There are numerous species of tapeworms in the environment, but the two most common that we see in pets are Dipylidium and Taenia species. These two species have a slightly different life cycle. Both live in the small intestine and anchor to the wall with mouth pieces in the head of their body. They are composed of multiple, small segments that mature and eventually detach and are shed in the environment in the feces. These segments are around 6 mm in length and look similar to a rice segment. These segments are packed full of eggs, which then go on to complete their life cycle.
Dipylidium eggs are then ingested by the larval stage of a flea. Once the flea matures into an adult, it finds a dog or cat to feed on. When fleas bite a pet, it typically causes an itch response which leads them to lick and scratch. During this licking, pets can often ingest the flea (with the eggs of the tapeworm inside) and then complete the life cycle in the small intestine.
Taenia tapeworms are different in that they don't use fleas to transfer to another pet. After the eggs are shed in the feces, they are ingested by a intermediate hosts (mouse, deer, cow) and then hatch in the intestines. From here, they spread to other parts of the body and encyst in a small sac. The dog or cat then eats the intermediate host, thereby eating the tapeworm stage and completes the life cycle.
Many times you won't see any clinical signs when your pet has tapeworms. With heavy infections, you may see weight loss (even with a good appetite), diarrhea, or rectal itching. Without clinical signs, you may just see the tapeworms segments in the feces and that is all.
Because tapeworms are in a different family of intestinal parasites, they do require a different dewormer than hookworms, roundworms, and whipworms. The typical treatment is with a medication called pranziquantal. Typically only one injection or pill is needed; however, it may be suggested to repeat the treatment in a few weeks, especially in households where fleas are a problem and reinfection is possible.
I hope that these discussions on intestinal parasites were helpful. Please let me know if you have any questions about any of the common parasites that we see. With the warmer weather our next topic will be heartworm disease. Stay tuned.