Tapeworm Infection: Symptoms, Causes & Treatment (2024)

What is a tapeworm?

A tapeworm is a flat, parasitic worm that lives in the intestines of an animal host. It commonly infects many different animals, including humans, livestock and domestic cats and dogs (usually meat-eating mammals.)

Like other parasites, the mature tapeworm can only survive inside the host animal, feeding off of the host’s own nutrients. The head attaches to the inside of your intestines and absorbs nutrients from the food digesting there.

Meanwhile, the body continues to grow and lay eggs. The eggs pass through the intestines of the host animal and out of their body in their poop. This is how the eggs will find their new host.

What do tapeworms look like?

The tapeworm gets its name from its flat shape, resembling a tape measuring ribbon. The body grows in segments. The tapeworm has three distinct parts: a head, which attaches to the host, an unsegmented neck, where new body segments generate from, and the segmented lower body.

Each body segment produces its own eggs. In some species, the segments break off with the eggs to pass through the intestines of the host in their poop. The segments look like little grains of white rice. Segments in poop are often the first visible sign of a tapeworm infection.

What is a tapeworm infection?

Tapeworm infection comes in two forms:

Intestinal tapeworms

Intestinal tapeworms are adult tapeworms that have hatched and matured inside the intestines of a host animal. The mature tapeworms attach to your intestinal walls and absorb nutrients from the food digesting there. These tapeworms often cause no noticeable symptoms, and many people don’t realize they're infected. However, a severe infection can cause nutritional deficiencies, unexplained weight loss, nausea or diarrhea. Some tapeworms can live up to 30 years and grow up to 30 feet long.

You might hear your healthcare provider refer to your tapeworm infection as “taeniasis.” This term refers to an infection by tapeworms from the genus Taenia. Taenia solium (pork tapeworm), Taenia saginata (beef tapeworm) and Taenia asiatica (Asian tapeworm — also from pork) are all species that target humans as their definitive host. However, other species also infect human intestines, including Diphyllobothrium latum (fish tapeworm) and Hymenolepis nana (dwarf tapeworm — a smaller variety).

Invasive tapeworm larval infection

An invasive larval infection can happen if tapeworm larvae in your intestines migrate outside of your intestines and enter your bloodstream and other organs. The larvae adhere to your insides and form cysts there — pockets of fluid that grow around the larvae as they grow. These cysts can cause a variety of complications, depending on where they are. Cysts in your lungs, liver or heart can grow big enough to disrupt those organs’ normal functioning. Cysts that adhere to your spinal cord or brain can cause neurological symptoms, such as seizures.

You can have a larval infection with or without an intestinal tapeworm. The pork tapeworm Taenia solium causes both intestinal infections and invasive larval infection. (The larval infection is known as cysticercosis.) Other tapeworm species only infect humans as larvae. These infections go by different names depending on the species — cystic hydatid disease (echinococcosis), alveolar disease, sparganosis and coenurosis — but they all manifest in the same way, as cysts. Some cysts don’t cause any trouble, but some do and you may need someone to remove them.

How common is tapeworm infection in humans?

Tapeworm infection occurs around the world, particularly in countries where people commonly eat raw meat and fish and where sanitation is less rigorous. In the U.S., tapeworm infection is rare, but U.S. citizens can get an infection while traveling and bring it back with them. Worldwide, tapeworm infection rates are difficult to measure. Tapeworms often cause no noticeable symptoms, and many countries lack the resources to diagnose everyone who has symptoms. They may be more common than we can tell.