البوم لبويضات ال Hymenolepis nana

Hymenolepis
nana

Hymenolepis
nana egg in wet mounts.

Eggs of Hymenolepis nana.
These eggs are oval and smaller than those of H. diminuta, with a
size range of 30 to 50 µm. On the inner membrane are two poles,
from which 4-8 polar filaments spread out between the two membranes.
The oncosphere has six hooks.


A	B

A, B: Eggs of H.
nana in an unstained wet mount. Note the presence of hooks in
the oncosphere and polar filaments within the space between the
oncosphere and outer shell.


C	D

C: Egg of H. nana in
a wet mount. Image courtesy of the Georgia Department of Public
Health.
D: Egg of H. nana in an unstained formalin ethyl
acetate (FEA) wet mount. In this image, four of the hooks in the
oncosphere are clearly visible. Image courtesy of the Oregon State
Public Health Laboratory.


E	F

E, F: Eggs of H.
nana in an unstained wet mount. In these two images, the polar
filaments in the space between the oncosphere and outer shell are
clearly visible.

Life
cycle of Hymenolepis
nana.

البوم لبويضات ال Hymenolepis nana H_nana_LifeCycle

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
,
attach to the intestinal mucosa and develop into adults that reside
in the ileal portion of the small intestine producing gravid proglottids
.
Eggs are passed in the stool when released from proglottids through its
genital atrium or when proglottids disintegrate in the small intestine
.
An alternate mode of infection consists of internal autoinfection, where
the eggs release their hexacanth embryo, which penetrates the villus
continuing the infective cycle without passage through the external
environment
.
The life span of adult worms is 4 to 6 weeks, but internal autoinfection
allows the infection to persist for years.

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