How people get a tapeworm is likely dependent upon the species of tapeworm with which they are infected. With nearly every species, however, people get a tapeworm by ingesting the tapeworm in the larval form, and the larvae then migrate to different areas of the body where they eventually grow into full-sized parasites. The ways in which people ingest the larvae can include through uncooked or undercooked meat, by drinking infected water, or by accidentally ingesting larvae on unwashed hands.
Pets are more likely to get a tapeworm than people. The primary way in which pets get a tapeworm is by ingesting an infected flea. Pets, especially cats, are also vulnerable to tapeworm infection by eating a rodent or other small animal that is infected with a tapeworm.
Owing to the risk of tapeworms from fleas, practicing good flea control is a good measure to prevent pets and people from tapeworm infection. It is also important to treat a tapeworm infection in pets as soon as there is reason to suspect the pet may have a tapeworm. Children are especially vulnerable to tapeworm infection by getting larvae on their hands from an infected pet and then ingesting the larvae by failing to wash their hands. Children may also be susceptible to getting a tapeworm by accidentally swallowing an infected flea or louse.
The beef tapeworm, Taenia saginata, is primarily contracted from beef. In most instances, people get a beef tapeworm by consuming undercooked beef. This tapeworm can grow to 25 feet (7.5 m) in the human intestines.
The pork tapeworm, Taenia solium, is primarily contracted by eating undercooked pork. People can also get the pork tapeworm by eating other foods or drinking water that is infected. This tapeworm can grow to 21 feet (6 m) in the human intestines.
The fish tapeworm, Diphyllobothrium latum, is contracted from eating undercooked fish. This fish can grow up to 25 feet (7.5 m) in the human intestines. The dwarf tapeworm, Hymenolepis nana, is contracted by eating feces-contaminated food. It is small in comparison to other tapeworm species and grows to only about 12 inches (about 30 cm).
The most common symptoms of a tapeworm infection are nausea, diarrhea, and weight loss. Some people will also experience abdominal pain, fatigue, and unexplained fever if they get a tapeworm. In many instances, there are no symptoms when people get a tapeworm. In rare instances, tapeworm infection can cause more serious symptoms.
In addition to treating pets for fleas and tapeworm infection, there are other steps to prevent tapeworm infection in people. This prevention includes good hand-washing hygiene and not eating undercooked meats. Children should also be taught to wash their hands before eating, after using the bathroom, and after playing with pets.