Adult tapeworm infections Hymenolepiasis is caused by two

Adult tapeworm infections Hymenolepiasis is caused by two cestodes (tapeworms) species: 1. Hymenolepis nana: The dwarf tapeworm. 2. Hymenolepis dimnuta: The rat tapeworm. A cestode of rodents infrequently seen in humans and frequently found in rodents.

Hymenolepis species Genus is derived from the membranous character of the egg shell “hymen”. Ø 3 testes in each mature segment. Ø Uterus is sac-like and transverse. Ø Eggs possess two membranes’ outer membrane is thin and transparent. Ø larval stage is called cysticercoid. Small bladder containing the invaginated head proximally and a solid, elongated portion as a caudal appendage. Ø There are 2 species: n Hymenolepis nana n Hymenolepis diminuta Ø

Hymenolepis nana Disease: Hymenolepiasis or Dwarf tapeworm infection

Notes: n Smallest tapeworm infecting man. n Found worldwide. n Mainly among children. Infection more in school children and institutional population. n The infection is primarily limited to children in warm climates. n Only human tapeworm that can complete its life cycle in a single host. n Man can harbour both the adult and larval stages of the parasite.

n No intermediate host is required in some infection. n It can utilized fleas and beetles for development of cesticercoid. n Exception to the general rule that “Helminths do not multiply inside the body of the definitive host”. n Parasite of small intestine.

Morphology: v. H. nana is the smallest of the tapeworm of man. v. It length is 25 -40 mm. X 1 mm. ( it contain 200 proglottids and they are broader than their long). v. Scolex is provided with four suckers and rostellar crown of 2030 minute hooklets. v. The neck is long and slender.

Morphology: Adult: n n n Found in the ileum. Delicate strobila. Worms may be present in large numbers from 1, 000 8, 000. Short life span, about 2 weeks. Transverse uterus. 3 testes.

194 ( 1 – 4 cm ) Methylene blue s. Hymenolepis nana

Morphology: Scolex n Subglobular. n 4 suckers. n Provided with a short retractile rostellum armed with a single row of 20 -30 hooklets. n Rostellar hooklets are shaped like tuning forks.

Retractile rostellum with hooks scolex of Hymenolepis nana

v Mature segment: wider than long testes 3 globes mid-lateral genital pore. v Terminal gravid proglottids usually disintegrate before separating from the strobila, so that the eggs are randomly mixed with the feces. Genital pores gravid proglottid mature proglottid

Mature Proglottids of H. nana Gravid Proglottids of H. nana segments

Eggs are spherical, measured 30 -47µm. There are two thin membranes shells, the inner one of which has polar thickenings, each provided with 4 -8 long thread like filaments extending into the space between the inner and outer shell. v The egg floats in saturated solutions of common salt. v

Saline s. Iodine stain H. nana eggs, stool smear

v. Cysticercoid larvae (a small solid larva with the scolex enveloped by tissue of its body). Cysticercoid of Hymenolypis spp.