Compare and contrast infection with Taenia saginata and Echinococcus granulosus in humans, including the consequences of the infections.

Question

What will be an ideal response?

Answer 1

Both of these parasites are cestodes (tapeworms) that are acquired by ingestion. Humans are the definitive host for T. saginata and become infected when they consume undercooked beef containing the immature larvae in the form of cysticerci. The larvae emerge in the intestine, attach to the wall, begin feeding, and mature into self-fertilizing adults. The humans pass the eggs in their feces. Intestinal infection with the adult tapeworm may be asymptomatic, but patients may experience diarrhea, nausea, abdominal pain, and weight loss.

Humans are accidental intermediate hosts of E. granulosus, a parasite of canines. Humans become infected when they ingest the tapeworm eggs, which hatch in the intestine. The larvae then burrow out of the intestine and take up residence in a variety of organs ranging from the liver to the brain. The larvae of E. granulosus are capable of asexual reproduction in intermediate hosts, so the cysts established by the larvae continue to increase in size (and number of larvae) throughout the lifetime of the host. Eventually, the expanding cyst damages the organ in which it resides, and the condition may progress to organ failure. As a consequence, the human hosts experience a range of symptoms determined by the organ(s) being damaged (e.g., declining liver function to the point of failure or brain damage may mimic a tumor). Humans are considered dead-end hosts for E. granulosus because their flesh is rarely consumed by the definitive host.