Morphology, Life cycle, and Lab diagnosis of Taenia  saginata (Beef Tapeworm).

Morphology of Taenia saginata (Beef tapeworm or unarmed tapeworm of man)

It is found in the human intestine of persons who eat beef meat. Its intermediate host is cattle and buffaloes. It is longer than Taenia solium. It moves in the human intestine from the lower end of the small intestine to the upper end of the small intestine.

There are two forms of Taenia saginata. These are Adult beef tapeworm and its egg.

Adult beef tapeworm: Its length varies from 5 to 10 mitres. In some cases, its length may extend to 25 meters. There are three parts in adult beef tapeworm. These are Scolex, Neck, and Strobila.

• 1. Scolex: It is knob shaped structure at the anterior end of an adult beef tapeworm and is the head of an adult beef tapeworm. Its diameter is up to 2mm. It does not have hooklets, Rostellum but it has four adhesive suckers.

• 2. Neck: It is present between the neck and scolex. It is a long, narrow, and fragile structure.

• 3. Strobila: The number of proglottids is between 1000 to 2000. There are three types of proglottids in Taenia saginata. These are immature proglottides, mature proglottides and gravid proglottides.

  • · Immature proglottides: They are present in the anterior part of the strobila. They are young proglottides and do not contain reproductive organs.

  • · Mature proglottides: They are present in the middle part of strobila. Well developed both male reproductive organs and female reproductive organs are present in these proglottides. The uterus is unbranched.

  • · Gravid proglottides: They are present at the posterior part of the strobila. Reproductive organs disintegrate but a branched uterus filled with fertilized eggs is present. They shed out from the strobila and are called apolysis.

Morphology of beef tapeworm eggs

The morphology of beef tapeworm (Taenia saginata)and pork tapeworm (Taenia saginata) eggs are the same.

Eggs are spherical in shape and golden brown in color. The golden brown color of eggs is due to staining of eggs with human bile. Eggs are covered with transparent film and found in clumps. Eggs have embryos thus also called Oncosphere. The life span of the oncosphere is 8 weeks. It does not float on a saturated saline solution. They can infect cattle but not humans.

Life cycle of T. saginata (Beef Tapeworm)

The life cycle of Beef Tapeworm is complex and involves multiple hosts. Human and carnivorous animals are the definitive hosts (primary hosts) of the Taenia saginata. Cattle, buffaloes, and herbivorous animals are the Intermediate hosts (Secondary hosts) of the Taenia saginata.

• 1. Egg: The life cycle of Beef Tapeworm begins with the egg. These eggs are excreted from the human host body with stool.

2. Intermediate host: Herbivorous animals such as Cattle and buffaloes are the intermediate host of the Taenia saginata. Tapeworm eggs enter their body with the contaminated water and vegetation.

3. Larva development: Tapeworm eggs release larvae inside the intermediate host's body. These larvae are called Oncospheres. Oncospheres penetrate the intestinal wall of the intermediate host and migrate to various tissues of the heart, lungs, and muscular tissues. Inside tissue, they form fluid-filled cysts called cysticerci.

4. Definitive host infection: Infected intermediate hosts are eaten by the definitive host. Carnivorous animals and humans are the definitive hosts of the Tapeworm. Definitive hosts get an infection after consuming raw or undercooked meat (intermediate host) containing cysticerci. Cysticerci can survive up to six months.

5. Adult Tapeworm: Cysticerci develop into adult Beef Tapeworms inside the intestine of the definitive hosts. It takes 2 to 3 months. They attach to the intestine wall by using a scolex (Head). They grow and develop segmented bodies. Each segment is called proglottids. Tapeworm is hermaphrodite. Both sexes are in the same body. Each proglottid has both sex organs. Proglottids continuously produce eggs.

6. Eggs release: Mature proglottids (Gravid proglottids)containing eggs are at the end of the Beef Tapeworm body.