2. INTRODUCTION
Common name: The old world hookworm
The parasite was first discovered in 1838 by
an Italian physician Angelo Dubini.
Geographical distribution:
It is widely distributed in all tropical and sub
tropical countries.
It is found in Europe, North Africa, India
(Punjab and U.P)
3. Contd…..
Habitat: The adult worm lives in the small
intestine of man, particularly in the jejunum.
Morphology:
It is small, greyish white, cylindrical worm.
It appears reddish brown when freshly
passed in faeces due to ingested blood in its
intestinal tract.
The anterior end of the worm is bent slightly
dorsally, hence the name hookworm.
4. Contd…
The buccal cavity is armed with two pairs of
teeth and two knob like plates.
It has both digestive and excretory system.
There are 5 glands connected with the
digestive system, one of them called an
oesophageal gland, secretes a ferment which
prevents the clotting of blood from the site of
bite.
5. Contd…
Male
Size: Smaller, 8mm in
length.
Shape of tail:
Expanded in an umbrella
like fashion(copulatory
bursa).
Genital opening:
Posteriorly opens with
cloaca.
Female
Size: Longer than male
12.5mmin length.
Shape of tail: Tapering,
no expanded bursa.
Genital opening:
middle third of the body
6. Contd…
The worm assumes a Y-shaped figure during
copulation.
Copulatory bursa: This consist of 3 lobes : 1
dorsal and 2 lateral. Each lobe is supported by
chitinous rays; Total number of rays are 13.
Life span of the adult worms is about 3-4
years.
10. Eggs
- Oval or elliptical in shape measuring 65x40um.
- Colourless.
- Surrounded by a transparent hyaline shell
membrane.
- Contains a segmented ovum usually with 4
blastomeres ; has a clear space between the egg
shell and segmented ovum.
- Floats in saturated solution of common salt.
- The eggs when passed out in faeces, are not
infective to man.
13. Larvae
- There are 2 types of larva Rhabditiform larva and
Filariform larva.
- The Rhabditiform larva (250um in length )
hatches out in soil in 48hrs.
- The Rhabditiform larva moults twice, on 3rd day
and 5th day, it then develops into filariform larvae
(500-600um) in length. This is the infective stage
of parasite.
- The time taken for the development from eggs to
filariform larvae is on an average 8-10 days.
14. Life Cycle
No intermediate host is required. Man is only
the definitive host for A. duodenale.
The various stages of life cycle are as
follows:
Stage I: Passage of eggs from infected host:
The eggs containing segmented ova
with 4 blastomeres, are passed out in the
faeces of the human host.
15. Contd……
Stage II: Development in soil:
- From each egg a Rhabditiform larva (250um in
length) hatches out in the soil in about 48 hours.
- The Rhabditiform larva moults twice (3rd and 5th
day)
- Later it then develops into a filariform larva (500-
600um) in length, the infective stage of the
parasite.
- The time taken for development from egg to
filariform larvae is 8-10 days.
16. Contd…
Stage III: Entrance into a new host:
The filariform larva are infective to
man. The larvae gain entrance to the body by
penetrating the skin.
Stage IV: Migration:
The larvae penetrate the skin and
enter into the lymphatics or small venules. It is
then carried to the heart and lungs. In the lungs,
it breaks the capillaries and enters the alveoli.
They then migrate on to the bronchi, trachea and
17. Contd…
larynx, crawl over the epiglottis to the back of the
pharynx and are ultimately swallowed. On entering the
oesophagus, a 3rd moulting takes place and a terminal
buccal capsule is formed.
Stage V: Localisation and Laying of eggs:
- The larvae settle down in the small intestine .
- The larvae with the help of buccal capsule, attach to
the intestinal mucosa and grows into an adult worm.
- In about a months they are sexually mature and
eggs are laid by the female. The eggs are passed in
stool and then the cycle is repeated.
19. Pathogenicity and Clinical features
The worm causes hookworm disease or
ancylostomiasis in man.
Mode of infection:
This occurs when man walks bare foot
on the faecally contaminated soil. The
filariform larvae penetrate directly through
the skin with which they come in contact. The
most common sites of their entry are:
20. Contd…
the thin skin between the toes.
the dorsum of the feet.
the inner side of the soles.
The larvae can penetrate any part of the
skin which is sufficiently thin.
- Infection may also occur by the accidental
drinking of water contaminated with filariform
larvae.
21. Contd…
Infecting agent: Filariform larvae
Migration: through lungs.
Portal of entry: skin
Site of localisation : small intestine.
Pathogenic effects: These may be considered
under two heads.
1. Pathogenic effect caused by Ancylostoma
larvae.
2. Pathogenic effect caused by Adult worms.
22. Contd…
1. Pathogenic effect caused by Ancylostoma
larvae.
a) Lesions in the skin:
i) Ancylostome dermatitis(ground itch)
ii) Creeping eruption.
Ground itch: occurs at the site of entry
disappears in 1-2 weeks.
24. Contd….
Creeping eruption: is a condition in which
filariform larvae wander about through the skin
for several weeks and months (upto 2 yrs)
producing a reddish itchy papule.
Lesions in the lungs:
Bronchitis and bronchopneumonia may
occur when the larvae break through the
pulmonary capillaries and enter alveolar space. A
marked eosinophilia occurs at this stage.
25. Contd…
2. Pathogenic effect caused by adult
worms:
The adult worm inhabit the
small intestine (jejunum of man , attaching
themselves to the mucous membrane by
means of their powerful buccal.
Anemia of microcytic hypochromic
type develops.
26. Contd…
Causes of anemia:
i) chronic blood loss: A duodenalae sucks
about 260ul ( 0.2ml ) blood per day, but a greater
amount of blood is lost by bleeding from the site
of bite. It is facilitiated by an anticoagulant like
substance secreted by the oesophageal gland.
ii) Nutritional defects: deficiency of the
available iron and haemopoietic substances in the
diet.
27. Contd…
- with iron deficiency a microcytic hypochromic
anemia.
- with deficiency of folic acid and vitB12 a
macrocytic type of anemia.
Clinical features:
This may be considered under
two heads;
28. Contd…
Gestrointestinal manifestation:
- duodenal ulcer
- abnormal appetite
- hypoacidity
- Achlorhydria
Effects of Anaemia:
- The skin assumes a swallow appearance
(light yellow color).
- The mucous membrane of the eye, lips and
tongue show extreme pallor(lack of color).
29. Diagnosis
- Examination of stool in the faeces.
- Detection of larvae in the sputum.
- Occult blood test positive.
- Blood examination shows eosinophilia.
Treatment:
- Albendazole 400mg once
- Ferrous sulphate 400mg thrice daily.
- Folic acid and vitB12
30. Contd….
Prophylaxis :
- Prevention of soil pollution by proper control
of sewage disposal.
- Personal protection – wearing of boots and
gloves.
