medical parasitology

1. Hymenolepis nana
By: Mr. Osman H. Ali
Lecture 15

2. Hymenolepis nana
is the most common human cestode, belongs to a large family known
as Hymenolepididae.
Hymenolepis nana previously known as vampiroleis nana.
Hymenolepis nana is the most common tapeworm in humans. It is also
known as the dwarf tapeworm due to its particularly small size (nana
meaning dwarf).
Definitive host of H.nana includes human, mice and rats, It is the
only cestode that does not require an intermediate host to develop into
its infective stage, intermediate host some time optional (various
species of beetles and fleas may serve as intermediate hosts)

3. Geographical distribution
Hymenolepis nana can be found
throughout the world, but is usually
most common in temperate zones.
Hymenolepis nana can be found
wherever humans and rodents live.
They have been found in almost all
types of terrestrial biomes
It is most often seen in children in
countries in which sanitation and
hygiene are inadequate

4. Hymenolepiasis
is the term when a human is infected with either H. diminuta or H.
Nana
Hymenolepis nana Hymenolepis diminuta

5. Morphology of H.nana
Adult worm are only 10-45 mm long and 0.5-
1 mm wide
Neck is long and slender
Whole H. nana adult worm with various stages of proglottid development stained for visibility

6. Morphology of H.nana
Scolex is small, 0.3 mm in diameter,
globular (rounded), cup-like.
Scolex situated at the anterior end,
has four suckers and retractile
rostellum with a single row of 20–30
hooks.
Genital pores are unilateral (side of
the segment)
Each mature segment contains three
testes

7. Morphology of H.nana
They have 100-200 segments that are wider
then they are long
Gravid (mature, full of eggs) proglottids are
0.2–0.3 mm long and 0.8–0.9 mm wide.
Proglottid is filled with eggs,
Each proglottid has both male and female
reproductive organs making Hymenolepis
nana hermaphroditic.
A proglottid copulates with itself or with
other segments of the same individual or
nearby H.nana.
Proglottids usually disintegrate in the
gastrointestinal tract and are rarely present in
the feces.

8. Morphology of H.nana
H. nana egg is colourless, almost transparent,
round to oval , 30–50 µm in diameter, has
polar filaments.
When shed in stool they are immediately
infective and survive up to 10 days in the
external environment,
they are embryonated and have a 6-hooked
oncospheres inside the shells.
Shell consists of two distinct membranes. On
inner membrane there are two small “knobs”
or poles from which 4–8 filaments arise and
spread out between the two membranes.

9. Morphology of H.nana

10. Life cycle of H.nana
Eggs of the tapeworm H. nana are infective when passed with the stool, but cannot survive
more than about 10 days outside the body.

11. Life cycle of H.nana
When eggs are ingested (in contaminated food or water or from hands contaminated with
feces), the oncospheres contained in the eggs are released.

12. Life cycle of H.nana
The oncospheres penetrate the intestinal villi and develop into cysticercoid (encysted) larvae.
Upon rupture of the villus, the cysticercoids return to the intestinal lumen, attach to the intestinal mucosa
and develop into adults that reside in the ileal part of the small intestine and produce gravid proglottids.

13. Life cycle of H.nana
Eggs, when released in the small intestine, are passed in the stool.

14. Life cycle of H.nana
*An alternate mode of infection occurs, known as internal autoinfection, where the eggs
release their oncospheres, which then penetrate the villi continuing the infective cycle without
leaving the host's body.

15. Life cycle of H.nana
The life span of adult worms is four to six weeks, but internal autoinfection can permit an
infection to last for years.

16. How we get infection with H.nana and what is symptomes
By accidentally ingesting tapeworm eggs.
by ingesting fecally contaminated foods and water
by touching your mouth with contaminated fingers
by ingesting contaminated soil.
Once you are infected, the dwarf tapeworm may cause auto infection where
the tapeworm may reproduce inside the body and continue the infection.
Symptoms are:
-Those who have symptoms may experience nausea, weakness, loss of
appetite, diarrhea, and abdominal pain. headache, itchy bottom, or
have difficulty sleeping.
-H. nana can be deadly in children or people with a weak immune system
-Dehydration can result from prolonged diarrhea.
-Sometimes infection is misdiagnosed as a pinworm infection.

17. Diagnosis
- Examination of the stool for eggs confirms the diagnosis.
-Seeing tapeworm in intestine.
Image byAkram from yüzüncü yıl hastanesi

18. Treatment
Treatment:
Praziquantel, adults and children, 25mg/kg in a single-dose therapy.
Alternatives:
Niclosamide: adults, 2 gm in a single dose for 7 days;
children 11-34 kg, 1 gm in a single dose on day then 500 mg per day orally
for 6 days;
children > 34 kg, 1.5 gm in a single dose on day then 1 gm per day orally for
6 days.
Nitazoxanide: adults, 500 mg orally twice daily for 3 days; children aged
12-47 months, 100 mg orally twice daily for 3 days; children 4-11 years, 200
mg orally twice daily for 3 days.
-Expect full recovery following treatment

19. Prevention
-Good hygiene
-Elimination of rats and mice
-Awell-balanced diet to promote resistance to infection
-Public health and sanitation programs