Hookworms
The hookworms cause hookworm disease, which is
one of the five major parasitic disease in China(malaria,
shistosomiasis,
filariasis,
kala-
azar
and
hookworm
disease). At least two species of hookworms infect man,
Necator americanus（美洲板口线虫）and Ancylostoma duodenale
（十二指肠钩口线虫）.
I.
They live in small intestine.
Morphology:
1.Adults: They look like an odd piece thread and are
about 1cm. They are white or light pinkish when living. ♀is
slightly larger than♂.The male’s posterior end is expanded to
form a copulatory bursa.
2.Eggs:
60 × 40 µm in size, oval in shape,
shell is thin and colorless. Content is 2-8cells.
3. The Morphological Differences between Two species of Hookworms
A. duodenale
Size
N. americanus
Size
larger
Shape
single curve, looks like C
Mouth
2 pairs of ventral teeth
1pair of ventral cutting plates
1pair with separate
1pair which unite to form a
Copulatory
Spicule
endings
♀caudal spine
♀vulva
smaller
double curves, looks like S
terminal hooklet
present
position
no
post-equatorial
pre-equatorial
4. Differences between Decorticated Ascaris and Hookworm eggs
______________________________________________________
Decorticated ascaris egg
hookworm egg
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Shell
thick
thin
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Egg cell
unsegmented
4-8cells
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Space between
Shell and cell
II.
new moon shaped space
between cell and ends of shell
empty space surrounding
the segmented cells
Life Cycle
1. Final host: man
2. Inf. Stage: Larva 3 or filariform larva
3. Inf. Route: by skin
4. Food: blood and tissue fluid
5. Site of inhabitation: small intestine
6. Life span: Ad 15years, Na 3-7years
7. Blood loss: (0.02-0.1)×7ml/Ad/day, 0.02-0.1ml/Na/day.
8. Blood-lung migration:III.
diagnosis
Methods:
1. saturated brine flotation technique
2. direct fecal smear
3. culture of larvae
IV.Requirements
1.Study the morphological characters of ova and adult worms of
hookworms
2.Realize the life cycle of the worm.
3.Master the methods of the diagnosis.
V. Individual observation
eggs and the adults
VI. work
Draw an egg of hookworm
Enterobius vermicularis
The pinworms are one of the most common intestinal
nematodes. The adult worms inhabit the cecum and colon.
Right after mating, the male dies. Therefore, the male worms
are rarely seen. The female worms migrate out the anus
depositing eggs on the perianal skin. Humans get this
infection by mouth and by autoinfection.
I.
Morphology
1. Adults: The adults look like a pin and are white in
color. The female worm measures about 8 to 13 mm in size
and is fusiform in shape. The male adult is only 2-5mm. The
tail of a male is curved. They die right after mating, thus
males are rarely seen. The anterior end tapers and is flanked
on each side by cuticular extensions called “ cephalic alae”.
The esophagus is slender, terminating in a prominent
posterior bulb , which is called esophageal bulb. The cephalic
alae and esophageal bulb are important in identification of
the species. .
2. Egg: 50 to 60µm by 25µm, persimmon seed-like,
colorless and transparent, thick and asymmetric shell,
content is a larva.
II. Life cycle
1. site of inhabitation: cecum and colon
2. infective stage: embryonated egg
3. infective route: by mouth
4. without intermediate host and reservoir
5. life span of female adults: 1-2 months
III. Diagnosis
Diagnosis depends on recovery of the characteristic eggs.
The eggs and the female adults can be removed from the
folds of the skin in the perianal regions by the use of the
cellophane tape method. The examination should be made in
the morning, before the patient has washed or defecated.
IV. Requirements
1.Study the morphological characters of ova and adult worms of
E. vermicularis
2.Realize the life cycle of the worm.
3.Master the methods of the diagnosis.
V. Individual observation
The eggs and the adults of E. vermicularis
VI. Work
Draw an egg of E. vermicularis