Tapeworms

Tapeworms are parasitic flatworms in the class Cestoda that inhabit the intestines of vertebrate hosts as adults. They have a long, segmented body anchored to the intestinal wall by a scolex, and they reproduce within each segment, called a proglottid. Tapeworms lack a true digestive system and absorb nutrients directly through their outer tegument.

Most tapeworms require one or more intermediate hosts to complete their life cycles. Eggs or gravid proglottids are shed in feces and can contaminate water or soil. Intermediate hosts ingest the eggs, leading to larval cysticerci in tissues. Humans typically acquire adult tapeworms by eating undercooked or raw meat or fish containing cysticerci. In the intestine, larvae mature into adults that can reach substantial lengths, with proglottids shed in the feces.

Several species affect humans, including Taenia saginata (beef tapeworm), Taenia solium (pork tapeworm), and Diphyllobothrium latum (fish tapeworm). Infections are often asymptomatic or cause mild abdominal discomfort, nausea, or weight loss. Taenia solium can occasionally cause neurocysticercosis when larvae migrate to the brain, a serious condition. Diphyllobothrium latum can lead to vitamin B12 deficiency.

Diagnosis relies on stool examination for eggs or proglottids, supported by imaging or serology for suspected tissue infections. Treatment options include praziquantel or niclosamide, depending on the species; neurocysticercosis may require albendazole with corticosteroids and, in some cases, surgery. Prevention centers on proper cooking of meat and fish, good hygiene, sanitation, and controlling intermediate hosts in the environment.