2. 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 and Ancylostoma duodenale.
They live in small intestine.
3. I. 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.
4. Adults of A. duodenale Adults of N. americanus
Differences between two hookworms
5. Scanning electron micrograph of the mouth
capsule of Ancylostoma duodenale, note the
presence of four "teeth," two on each side.
6. Scanning electron micrograph of the mouth
capsule of Necator americanus, another species of
human hookworm. Note the presence of two
cutting "teeth“.
9. Left picture: Copulatory bursa and spines of N.
americanus(a side view);
Right picture: copulatory bursa of A. duodenale(a
top view)
10. Morphologically it is
not possible to
differentiate between
A. duodenale and N.
americanus.
Interference contrast.
×400. Enlarged by 5.4.
11. 3.The Morphological Differences between Two
species of Hookworms
_____________________________________________________
A. duodenale N. americanus
______________________________________________________
Size larger smaller
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Shape single curve, looks like C double curves, looks like S
______________________________________________________
Mouth 2 pairs of ventral teeth 1peir of ventral cutting plates
____________________________________________________________
Copulatory circle in shape oval in shape
Bursa (a top view) (a top view)
____________________________________________________________
Copulatory 1pair with separate 1pair of which unite to form
spicule endings a terminal hooklet
_______________________________________________________
caudal spine present no
_______________________________________________________
vulva position post-equatorial pre-equatorial
_______________________________________________________
12. II. 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-lung migration:
skin, cavum, right heart, lungs
14. III. Pathogenesis and Clinical Manifestations
1. Larval migration
(1) Dermatitis, known as "ground itch" or "stool
poison".The larvae penetrating the skin cause
allergic reaction, petechiae 0r papule with itching
and burning sensation. Scratching leads to
secondary infection.
(2) pneumonitis (allergic reaction), Loeffier's
syndrome: cough, asthma, low fever, biood-tinged
sputum or hemoptysis, chest-pain, inflammation
shadows in lungs under X-ray. These manifestations
go on about 2 weeks.
15. 2. Adults in small intestine
(1) Epigastric pain as that of a duodenal ulcer.
(2) A large worm burden results in microcytic
hypochromatic anemia (character manifestation). The
symptoms are lassitude, edema, palpitation of the heart.
In severe case, death may result from cardiac failure or
physical exhaustion.
(3) Allotriophagy (orpica) is due to the lack of trace
element iron .
(4) Amenorrhea, sterility, abortionmay take place in
women.
(5) Gastrointestinal bleeding
(6) Infantile hookworm disease
17. Iv. Diagnosis
Criterion: 1. hemoglobin is lower than 120g/L in man, 110g/L in
woman. 2. find hookworm egg
Method:
1. saturated brine flotation technique
2. direct fecal smear
3. culture of larvae
V. Treatment
1. Albendazole 2. Mebedazole
VI. Epidemiology
worldwide distribution. 22-26℃ is the optimal temperature for
Ancylostoma duodenale development, Ancylostoma duodenale
mainly prevalent in north of China. 31-35℃ is suitable for Necator
americanus, it is mainly prevalent in south of China
VII. Prevention
Unified measures: 1. sanitary disposal of night soil, 2. individual
protection, 3. health education, 4. cultivate hygienic habits, 5.
treat the patients and carriers.
