The lifecycle of

A diagram showing the lifecycle of Hymenolepis microstoma.

Various flour beetles (e.g. Tribolium and Tenebrio spp.) may act as first intermediate hosts, becoming infected following ingestion of eggs from mice faeces or egg contamination in their environment.

Oncospheral larvae are released from the eggs and use hooks and secreted enzymes to penetrate the gut of the beetles and enter the haemocoel.

In the haemocoel the larvae undergo complete cellular reorganization (ie metamorphosis), transforming into cysticercoid larvae in approximately 7 days.

Mice become parasitized via predation of infected beetles. Ingested cysticercoids excyst in the stomach of the mice and enter the small intestine where they eventually emigrate to the bile duct.

By approximately 5 days post-infection they become strobilate (segmented) worms and by day 10 they are producing infective eggs.

Adult worm infections in mice held under laboratory conditions persist for 6--12 months. Longevity of the larval cysticercoid stage in the beetle may be as long as the lifespan of the adult beetle (up to 3 years), although any age-related decrease in viability has not been studied.