Taenia saginata
المؤلف:
Patricia M. Tille, PhD, MLS(ASCP)
المصدر:
Bailey & Scotts Diagnostic Microbiology
الجزء والصفحة:
13th Edition , p686
2025-11-03
53
GENERAL CHARACTERISTICS
T. saginata or beef tapeworm has a worldwide distribution and is more common than T. solium. The worm can grow 4 to 12 m and contain 1000 to 2000 segments. T. saginata may produce 100,000 eggs and live up to 25 years in the human intestine.
EPIDEMIOLOGY
T. saginata has a similar life cycle to that of T. solium. Cattle are the intermediate hosts and humans are infected through the ingestion of cysticerci (larval form) in raw or undercooked beef.
PATHOGENESIS AND SPECTRUM OF DISEASE
The life cycle of T. saginata begins with human ingestion of undercooked or raw meet infected with larvae. The larvae are ingested in the meat and, following digestion, released into the small intestine where the worm attaches to the mucosa and matures. In about 3 months, the worm may grow up to 4 to 5 m in length and gravid segments begin to break off and pass in stool. Following deposition of gravid segments in the soil, an intermediate bovine host may ingest the segments. The segments are digested and the eggs hatch, releasing an oncosphere that penetrates the muscle tissue. Following penetration of the mucosa the organisms are carried via the lymphatic vessels and bloodstream throughout the intermediate host. Humans then ingest the infected meat of the intermediate host, as previously indicated. Humans typically are asymptomatic, or have very mild indigestion, loss of appetite, vomiting, and abdominal discomfort. A rare case of severe infection may result in intestinal obstruction and appendicitis. Patients are often unaware of their infection until gravid motile segments are passed in the feces and cause psychological distress.
LABORATORY DIAGNOSIS
The stool should be examined for proglottids and eggs; eggs may also be present on anal swabs. The eggs of T. saginata are indistinguishable from those of T. solium. The uterus of T. saginata is longer than wide and typically contains 15 to 18 lateral branches on each side (see Figure 1). The scolex has four suckers and is unarmed or does not contain any hooklets (Figure 2). Stool specimens should be handled with care since the eggs cannot be distinguished from those of T. solium. Slight eosinophilia may develop.
Fig1. Gravid proglottids. A, Taenia saginata. B, Taenia solium. C, Diphyllobothrium latum. D, Dipylidium caninum. (From Garcia LS: Diagnostic medical parasitology, ed 5, Washington, DC, 2007, ASM Press.)
Fig2. T. saginata scolex with suckers. (Courtesy Dr. Henry Travers, Sioux Falls, S.D.)
ANTIPARASITIC SUSCEPTIBILITY AND THERAPY
Recommended treatment includes praziquantel or niclosamide. Treatment of T. saginata can be considered successful when no proglottids are passed for 4 consecutive months.
PREVENTION
Beef should be inspected for cysticerci and thoroughly cooked before ingesting.
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