Parasites In Humans
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Taenia Saginata - Beef Tapeworm

Taenia saginata is a large tapeworm that causes an infection called taeniasis. It is commonly known as the beef tapeworm or cattle tapeworm because it uses cows as intermediate hosts. Humans are the only definitive hosts. Taeniasis occurs worldwide and is relatively common in Africa, Eastern Europe, Latin America and the Philippines.

The life cycle of Taenia saginata starts, when eggs are passed in the feces of an infected human in a container called a proglottid or a tapeworm segment. They can survive a few months out in the environment. If a cow (the intermediate host) feeds on contaminated vegetation, it ingests mature eggs or gravid proglottids. In the small intestine larvae called oncospheres hatch, penetrate the intestinal wall, enter the bloodstream and migrate to muscle tissue (rarely to liver or other organs), where they encyst into cysticerci. The tiny cysticerci can survive for years and still be infective when humans eat the meat. If the beef is not cooked properly, cysticerci excyst in the small intestine and develop into adults within two months. Adults attach to the intestinal wall with their scolex using four suckers. The scolex has a pear-shaped and cup-like appearance reaching 1–2 mm in diameter. It is attached to the neck which starts to produce proglottids that make up the flat, long, segmented body also known as strobila. The proglottids mature and grow bigger as they get further from the neck. They are about 16–20 mm long and 5–7 mm wide and each proglottid has its own reproductive organs. They absorb nutrients through their membranes and produce up to 100 000 eggs per day. Proglottids break off from the tail and move with stool out of the human body. A full-grown Taenia saginata is whitish in colour and has about 1000–2000 proglottids and about six of them detach every day. The eggs usually stay inside the proglottids until they are out in the environment. When the proglottid dries up, it ruptures and releases the eggs. The eggs are embryonated, walnut brown and about 35 micrometers in diameter having a 6-hooked oncosphere inside its thick shell. If the feces land on grazing ground for cattle, a cow might accidentally ingest proglottids or eggs. Taenia saginata can live up to 25 years. It can grow up to 5 meters but in some cases can reach lengths of over 10 meters (coiled in the intestinal tract).

Taenia saginata life cycle

The disease is often asymptomatic. Taeniasis caused by Taenia saginata is more noticeable than taeniasis caused by Taenia solium (although T. solium is overall more dangerous because of the risk of cysticercosis). Heavy infection of Taenia saginata can cause some of the following symptoms:

  • Taenia saginataallergic reactions
  • constipation
  • diarrhea
  • dizziness
  • headache
  • loss of appetite
  • Taenia saginata proglottid (segment)nausea
  • obstruction of the bowel
  • stomach ache
  • weight loss.

Migrating proglottids can cause:

  • inflammation of the appendix)
  • inflammation of the bile duct)
  • unpleasant surprise when seen in the feces.

A full grown Taenia saginataYour health care provider makes the Taenia saginata diagnosis by identifying eggs or proglottids. Eggs and proglottids start appearing in the stool sample after three months of the start of the infection. During the first three months antibody detection methods can be used to find antibodies from a blood sample. All Taenia species have similar eggs so identification can only be done at the genus level. For educational purposes the specific species can be identified by examining gravid proglottids. The diagnosis can also be done during an endoscopic examination.

Treatment is traditionally done with an oral drug called praziquantel. It causes paralysis of the worm by opening its membrane calcium channels. Then through peristaltic movements the tapeworm is defecated out. Alternatively niclosamide can be used. Both drugs have some side effects (especially praziquantel) that are similar to actual tapeworm infection symptoms. Endoscopic treatment is available in some areas. In the endoscopic treatment a drug is injected straight to the small intestine. This causes all nearby tapeworms to detach and come out whole. If the scolex (and neck) is left behind, it might produce new segments.

To prevent infection:

  • Cook beef at or above 60 °C until it is no longer pink inside. Alternatively freeze the meat at or below -5 °C for a few days.
  • Prevent cattle from eating in areas, where vegetation might be contaminated with humans feces.