What is the pathophysiology of tapeworm infestation?

Updated: Apr 15, 2021
  • Author: Lisandro Irizarry, MD, MBA, MPH, FACEP; Chief Editor: Jeter (Jay) Pritchard Taylor, III, MD  more...
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Answer

When humans are the primary hosts, the adult cestode is limited to the intestinal tract. When humans are the intermediate hosts, the larvae are within the tissues, migrating through the different organ systems.

In most cestode infestations (ie, T solium, T saginata, Diphyllobothrium species, Hymenolepis species, and D caninum), humans are the primary hosts. Adult worms survive inside their human hosts, where they are limited to the intestinal tract. Human fecal contamination of the environment is needed to sustain these life cycles.

In the remaining cestodes (ie, Echinococcus species, Spirometra species, and T multiceps), humans function as the intermediate hosts. Larvae exist within the tissues and migrate through different organ systems.

Hymenolepis species and T solium are the only cestodes for which humans can function as both primary hosts and intermediate hosts. Hymenolepis diminuta is primarily a cestode of rodents, although humans can be a rare and accidental hosts in the life cycle. Humans are infected by swallowing insects that contain cysticercoid larvae, most often by ingesting mealworms or grain beetles that infest dried grains, cereals, flour, and dried fruit.

Table 1. Cestodes and Their Hosts (Open Table in a new window)

Cestode

Primary Host

Intermediate Host

T solium

Humans

Pigs, humans, dogs, cats, sheep

T saginata

Humans

Cattle

Diphyllobothrium

Humans

Fish

Hymenolepis

Humans

Hymenolepis nana: None; Hymenolepis diminuta: Rodents

D caninum

Humans, dogs, cats

Fleas on dogs/cats

Echinococcus

Dogs

Humans, sheep, cattle, goats, horses, camel

Spirometra

Humans

 

T multiceps

 

Hares, rabbits, squirrels, humans (rarely)

Diagram of the Echinococcus life cycle. Image cour Diagram of the Echinococcus life cycle. Image courtesy of the Centers for Disease Control and Prevention.

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