What to know
Taeniasis in humans is a parasitic infection caused by the tapeworm species Taenia saginata (beef tapeworm), Taenia solium (pork tapeworm), and Taenia asiatica (Asian tapeworm). Humans can become infected with these tapeworms by eating raw or undercooked beef (T. saginata) or pork (T. solium and T. asiatica). People with taeniasis typically have mild gastrointestinal symptoms or may be asymptomatic.
Overview
Once ingested, cysticerci attach to the small intestine and develop into adult tapeworms over the course of two months. The adult tapeworms produce proglottids that mature, detach, and migrate to the anus and are then passed in the feces.
T. saginata tapeworms are usually 4 – 12 m in length but can grow to be 25 m; the adult tapeworms produce 1,000 to 2,000 proglottids/ worm and may produce up to 100,000 eggs per worm.
T. solium (pork) tapeworms are smaller, 2 – 8 m in length, produce an average of 1,000 proglottids/worm, and may produce 50,000 eggs per worm.
T. asiatica tapeworms range in size from 4 – 8 m, produce 700 proglottids/worm and may produce 80,000 eggs per proglottid.
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Clinical features
Because of the large size of T. saginata tapeworms, T. saginata taeniasis is more frequently symptomatic compared to T. solium or T. asiatica taeniasis. Typical symptoms of taeniasis include mild epigastric discomfort, nausea, flatulence, diarrhea, or hunger pains. In some instances, passage of tapeworm segments is perceptible.
The most visible symptom of taeniasis is the active passing of proglottids through the anus and in the feces. In rare cases, proglottids may become lodged in the appendiceal lumen, or bile or pancreatic ducts.
Testing and diagnosis
Microscopic identification of eggs and proglottids in feces is diagnostic for taeniasis; however, eggs and proglottids are not released into the feces until approximately 2 – 3 months after the adult tapeworm is established in the upper jejunum. Repeated examination and concentration techniques will increase the likelihood of detecting light infections. Examination of 3 stool samples collected on different days is recommended to increase the sensitivity of microscopic methods. Eggs of Taenia spp. cannot be differentiated; a species determination may be possible if mature, gravid proglottids (or, more rarely, examination of the scolex) are present.
Recently developed coproantigen and molecular assays are more sensitive than stool examination, but these assays are not yet available outside of the research laboratory. Serologic methods, which are available only in research settings, may be used to identify T. solium tapeworm carriers.
Household contacts of neurocysticercosis cases should be evaluated for taeniasis to reduce the risk of cysticercosis.