Hookworms
Presented by: Mahamoud Ahmed & Faisal Farea
The disease induced by hookworms…was
never suspected to be a disease at all. The
people who had it were merely supposed to
be lazy, and were therefore despised and
made fun of, when they should have been
pitied.
---Mark Twain
Taxonomy
Kingdom: animalia
Phylum:Nematode
Class: secernentea
Order: Strongiloidae
Family: Ancylostomatidae
Genus: Necator/Ancylostoma
Species: A. duodenale and N. Americanus
Hookworms are the voracious blood feeders of the
nematode world.
Two principal species that infect
around 900 million people on earth
are:
Necator americanus known as the
american killer also known the new
world hookworm.
Ancylostoma duodenale known as
the old world hookworm.
Definitive host
Human
No Intermediate
host
Neactor americanus
N. americanus is the most
common species in humans in
most of the world. About 95%
of the hookworms in the
southern United States are
this species.
N. americanus has a pair of
dorsal and a pair of ventral
cutting plates surrounding the
anterior margin of the bucal
capsule
Males have bursa diagnostic
for the genus. The needlelike
specules have minute barbs
at their tips and are fused
distally.
Ancylostoma duodenale
Associated with miners
because mines offer an
ideal habitat for egg and
juvenile development due
to constancy in
temperature and humidity.
It was known to cause a
serious anemia in miners.
Has two ventral plates,
each with large teeth that
are fused at their bases. A
pair of small teeth is found
in the depths of the
capsule. The needlelike
specules have simple tips
and are never fused
Comparison of hookworms
Bucal cavity
Size of female
Size of male
Position of vulva
Egg production
Penetration
through skin
Longevity
Necator amricans
Ancylostoma
duodenale
Dorsal and ventral cutting
plates
2 ventral plates and
two large teeth
9-11mm
7-9mm
Mid-body
9000/ day
Yes
10-13
8-11mm
1/3 from
posterior
25000/ day
Yes
15 years
5 years
morphology
The eggs are bluntly rounded, thin
shelled, and are almost indistinguishable
between the different species. Measuring
60 by 40µm, the eggs of Ancylostoma
being slightly larger than those of Necator.
The adult parasites
are small cylindrical
worms, (Ancylostoma
duodenale being
slightly larger than
Necator americanus)
The male worm is
equipped with a
characteristic
copulatory bursa,
used to catch and hold
the female during
mating.
Geographic distribution
A.duodenale is the indigenous
hookworm of the north-temperate
zone of the eastern hemisphere. it is
confined in southern Europe, northern
Africa, India, China and southern Asia.
N.americanus is the new world worm.
the “American killer,” was first
discovered in Brazil and then Texas,
but it was later found indigenous in
Africa, India, Southeast Asia, China,
and southwest Pacific islands.
Question #1
The male is equipped with copulatory
bursa, used to catch…
a) food
b) female
c) prey
Life cycle
Life cycle
Eggs are passed with feces. Eggs hatch in about 48 hours
under favorable conditions such as (moist soil, protection
from direct sun rays and temperature about 25°C.
The first-stage larva feed upon bacteria in the feces about
three days and then molt to second-stage larva. First and
second stage larva have a rhabditiform esophagus. After 510 days they molt and become filariform third-stage larva
that are infective.
These infective larva can survive 3-4 weeks in favorable
environmental conditions. 25 -15°C at 0°C death occurs
rapidly. They move to the surface of the soil and wave back
and forth which increases the chance to contact host. When
they contact with the human host, the larva penetrate the
skin and are carried through the veins to the heart and
then to the lungs, break through into air sacs, to the
trachea and are swallowed. The larva reach the small
intestine, where they reside and mature in to adults.
Hookworms have evolved strategies to evade the
host’s defense system, and several of these has
been discovered.
Ancylostoma spp. Secrete a neutrophil inhibition
factor that interferes with activation of
neutrophils.
N. americanus secretes acetyl cholinesterase,
which inhabits gut peristalsis and possibly is an
anti-inflammatory factor.
Question #2
What conditions are required for the
eggs to hatch?
Moist soil & warm temp.
Symptoms/pathogenesis
Itching of skin as a result of penetration by the
larvae.
Congestion in lungs in heavy infections.
Anemia due to loss of blood, particularly if diet is
deficient.
Diarrhea
Persons with chronic hookworm disease are
debilitated.
Chronic heavy hookworm infection can damage
the growth and development of children.
Hookworm infection has been known to be fatal,
particularly in infants.
Hookworm infection/disease
Depends on three factors.
1)Number of worms present
2)Species of hookworm
3)Nutritional conditions of the
infected
person.
In general fewer than 25 N.americanus in person
will cause no symptoms. 500-1000 result in
severe symptoms, and more than 1000 may lead
fatal consequences.
Ancylostoma spp. Suck more blood than
N.americanus fewer worms cause greater
disease. 100 worms cause severe symptoms.
Transmission
Hookworm infection is contracted from
contact with soil contaminated by
hookworm, by walking bare foot or
accidentally swallowing contaminated soil.
Children are at high risk because they play
in dirt and often go bare foot.
Hookworms can’t be spread person to
person.
Diagnosis/treatment
Recovery of the eggs in stool
samples.
Mebendazole or albendazole. It
should not be given to pregnant
women.
Question #3
T/F hookworm infection can be
transmitted person to person?
False
Prevention
Proper sanitation practices.
Appropriate fecal disposal.
Do not walk barefoot or contact with
bare hands in areas where
hookworms is common or there are
likely to be feces in the soil or sand.
Questions from the article
Which stage of larvae feed on bacteria?
Rhabditiform.
To become infective stage the rhabditiform
has to molt?
a) 2 times
b) 3 times
C) 1 time
d) 4 times.
Cont..questions.
Which part of the world the
N.americanus is found?
Central/south. Africa, s. Asia,
Australia and pacific islands.
Which of the worms suck more
blood?
A.duodenale
Works cited
http://www.dpd.cdc.gov/DPDx/HTML
/Para_Health.htm
http://www.dpd.cdc.gov/DPDx/HTML
/Para_Health.htm
http://pathmicro.med.sc.edu/parasit
ology/nematodes.htm