An oncosphere is the larval stage of a tapeworm that hatches from the egg after being consumed by an intermediate host.

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Tapeworms (cestodes) are a class of flatworms (platyhelminths) that are segmented and utilize suckers or hooks located at their head region (scolex) to attach to the wall of the host's small intestine.

Tapeworms (Cestodes)

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Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

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The scolex is the head region of a tapeworm (cestode) that contains suckers or hooks used by the parasite to attach to the wall of the host's small intestine.

Scolex

Proglottids are the segments that compose the body of a tapeworm, each containing reproductive organs that detach upon fertilization of the gametes to release gravid segments filled with eggs.

Proglottids

Oncosphere

Cysticerci are the larval cysts of tapeworms that develop within the tissues or organs of an intermediate host after the migration of the oncosphere.

Cysticerci

*Taenia saginata*, commonly known as the beef tapeworm, is a species of tapeworm that infects humans through the consumption of undercooked, contaminated beef. It is relatively benign, residing in the intestine and causing minor digestive issues or occasional allergic reactions.

*Taenia saginata*

*Diphylobothrium latum* is the largest species of tapeworm that infects humans, reaching lengths of up to $${}15$$ meters, and is acquired by eating undercooked, contaminated fish.

*Diphylobothrium latum*

*Echinococcus granulosus*, commonly known as the dog tapeworm, is a parasitic tapeworm that can infect humans and utilizes dogs as an important host.

*Echinococcus granulosus*

*Taenia solium*, commonly known as the pork tapeworm, is a species of tapeworm that infects humans through the ingestion of undercooked, contaminated pork. Its larvae can migrate from the intestine to colonize other tissues, such as skeletal and smooth muscle, and the central nervous system, where they form cysticerci and cause neurocysticercosis.

*Taenia solium*

The life cycle of *Taenia* tapeworms begins when eggs or gravid proglottids are released from an infected host into the environment. Intermediate hosts, such as cattle (*T. saginata*) or pigs (*T. solium*), ingest contaminated vegetation. The eggs hatch into oncospheres, which penetrate the intestinal wall, travel through the circulation to muscles, and develop into infective cysticerci. Humans, the definitive hosts, become infected by consuming raw or undercooked meat containing these cysticerci. In the human small intestine, the tapeworm's scolex attaches to the intestinal wall, where it develops into an adult worm.

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