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Helminths(General Features)
1..Helminth Greek word means Worm.
2. Their outer covering which is resistant to
intestinal digestion is called cuticle.
3. Their mouth is provided with teeth/cutting
4. Hooks are for attachment to host.
5.Helminths do not possess complete digestive
system and depend on predigested
nutrients available from the host.
Helminths(General Features
6.Males are smaller than females.
7.They do not multiply in the host.
Classification(Worm Shape)
1..Nematodes: (Cylindrical shape,unsegmented)
s,Ascaris lumbricoides,Trichinella spiralis
2. Trematodes: (Leaf-like called
Shistosomes,Fasciola hepatica
3. Cestodes: (Tape-like,segmented)
T saginata, T solium, E granulosus, D latum,
H nana
General features of
1..The name nematode means threadlike.
2.Nematodes are elongated, cylindrical,
unsegmented worms with tapering
3.They are bilaterally symmetrical.
4.The adults vary in size from about 1mm
to about 1 meter in length.
General features of
5.The body is covered with a tough
smooth cuticle.
6.The sexes are separate.
7.Nematodes may produce
eggs(oviparous),or larvae(viviparous).
Some lay eggs containing larvae
General features of
8.The life cycle consists of 4 larval stages
and the adult form. The cuticle is shed
from one stage to another.
9.The shedding of cuticle in order to
acquire new growth is called Moulting.
Ancylostoma duodenale(Hook
1.Live in small intestine mostly jejunum.
2.They are reddish brown in color due to
ingested blood.
3.Anterior end curved, hence name hook worm
4.Male 8-11mm in length and 0.4mm thick.
5.Female 10-13mm in length and 0.6mm thick.
6.Eggs are oval containing 4-8 segmented
ovum measuring 6oµm by 40µm.
Adult forms male and female
Ancylostoma duodenale is found in
1.Pakistan and India
2.Middle East
3.North Africa
It infects about 1 billion people of the
world(1/5 of world population is
Life Cycle
1.Eggs passed in feces. In sandy soil develop
into rhabditiform larva in two days which is
non-infectious and feed on vegetation. It is
about 250µm long.
2.On 3rd or 5th day infective filariform larva
develops after two moults which does not
feed and wait for human host. It is about
500µm long.
3.When person walks bare-footed it penetrates
the skin.
Life Cycle(Contd:)
4.Then enters S/C tissue and penetrates into
5.Through blood circulation reaches right side
of heart and then in lungs.
6.Then it breaks out the capillaries to reach
7.Migrates upwards, crawls over epiglottis,
reaches jejunum when swallowed.
Life Cycle(Contd)
8.In jejunum it matures into male or
female adult after two moults. It takes
about 6 weeks to become sexually
9.In small intestine they attach to the
intestinal wall and feed on blood.
10.After mating female produces eggs
and cycle is repeated.
Egg of Ancylostoma duodenale
Rhabditiform larva
Filariform larvae
Life cycle
Pathogenesis and C/F
1.Local itching where larva enters skin
and if it is associated with secondary
bacterial infection it is called ground
2.Pneumonitis and cough.
Pathogenesis and C/F(Contd:)
4.Iron deficiency anemia(Hypochromic
microcytic anemia)
5.Epigastric pain, vomiting
6.Diarrhea,reddish/black stools
1.Presence of eggs in feces by direct
2.Adult hook worm may be seen in feces.
4.Microcytic hypochromic anemia.
Egg of Ancylostoma duodenale
Adult forms male and female
1.Mebendazole / Pyrantel pamoate.
2. Iron to treat iron deficiency anemia.
1.Do not defecate in places other than
latrines, toilets.
2.Do not walk barefooted.