Eggs of Hymenolepis nana are immediately infective when passed with the stool and cannot survive more than 10 days in the external environment
When eggs are ingested by an arthropod intermediate host
(various species of beetles and fleas may serve as intermediate hosts), they develop into cysticercoids, which can infect humans or rodents upon ingestion and develop into adults in the small intestine. A morphologically identical variant, H. nana var. fraterna, infects rodents and uses arthropods as intermediate hosts. When eggs are ingested
(in contaminated food or water or from hands contaminated with feces), the oncospheres contained in the eggs are released. The oncospheres (hexacanth larvae) penetrate the intestinal villus and develop into cysticercoid larvae
Upon rupture of the villus, the cysticercoids return to the intestinal lumen, evaginate their scoleces