Hymenolepiasis and Lifecycle of Hymenolepis nana Larvae

Oval with a thin wall, smaller than Hymenolepis diminuta eggs. Oncospheres have six hooks.

Most often asymptomatic, but heavy infections can cause weakness, headaches, anorexia, abdominal pain, and diarrhea.

Rodents are the primary hosts of H. diminuta.

Humans can get infected by ingesting fleas contaminated with cysticercoid larvae.

The adult tapeworm lives in the small intestine of rodents, and humans get infected by ingesting fleas containing cysticercoid larvae.

Morphology of H. nana eggs is small, oval, and has a polar thickening called the operculum.

Symptoms of Hymenolepiasis in humans include abdominal pain, diarrhea, and weight loss.

Definitive host of H. diminuta includes humans or rodents, and the intermediate host is arthropods.

H. diminuta is transmitted to humans by ingesting an intermediate host carrying the cysticercoid larvae.

In the life cycle of H. diminuta, eggs are passed in the stool, ingested by an arthropod intermediate host, and develop into cysticercoid larvae.

1st Intermediate host: Freshwater crustaceans. 2nd intermediate host: Freshwater small fish. 3rd paratenic host: Freshwater larger fish.

By eating raw or undercooked freshwater fish infected with the plerocercoid larvae.

Hymenolepis nana eggs are unembryonated when passed in human feces and become embryonated later.

Symptoms of Hymenolepiasis include abdominal pain, diarrhea, and weight loss.

Unembryonated eggs are passed in human feces, become embryonated later, hatch in freshwater, develop into ciliated coracidia, ingested by crustaceans, develop into procercoid larvae, then small fish ingest the infected crustacean and produce plerocercoid larvae within their tissues.

Cyclophyllidean tapeworms possess a branched uterus with lateral genetical pores and produce non-operculated eggs that generate non-ciliated larvae.