Paelussid

Paelussid, typically translated as tapeworms, are a group of parasitic flatworms in the class Cestoda that inhabit the digestive tracts of vertebrate hosts, including humans. They have a simple body plan consisting of a scolex for attachment, a neck, and a chain of segments called proglottids that make up the strobila. Tapeworms lack a true mouth and digestive system; they absorb nutrients directly through their tegument from the host’s digested food.

Life cycles usually involve one or more intermediate hosts. Eggs or gravid proglottids are released in the host’s feces and contaminate the environment. If an intermediate host ingests the eggs, larvae develop within its tissues; the definitive host becomes infected by consuming undercooked meat or fish containing these larvae. In humans, common examples include Taenia species (causing taeniasis) from beef or pork, and Diphyllobothrium latum (fish tapeworm). Echinococcus species can cause hydatid disease when their eggs are ingested, and Hymenolepis species can infect humans directly.

Clinical presentation varies. Many infections are mild or asymptomatic, but heavy worm burdens can cause abdominal discomfort, weight loss, and nutritional deficiencies. Certain tapeworm infections can lead to severe disease if larvae migrate to tissues, as seen with cysticercosis caused by Taenia solium or echinococcosis.

Diagnosis typically relies on identification of eggs or proglottids in stool, supported by imaging or serology when tissue involvement is suspected. Treatments include antiparasitic drugs such as praziquantel or albendazole, with different regimens depending on the species and burden. Prevention focuses on proper cooking of meat and fish, good hygiene, and sanitation to limit environmental contamination with eggs.