The document discusses several nematode parasites including Ascaris lumbricoides (roundworm), the hookworms Ancylostoma duodenale and Necator americanus, and Strongyloides stercoralis (threadworm). It provides details on the life cycles, diagnostic stages, geographic distribution, and distinguishing morphological features of these parasites. Comparative information is given on the rhabditiform and filariform larvae and eggs of hookworms and Strongyloides stercoralis.

1. Medical Parasitology
Lab8, part 2
:Prepared by
NASR A. Sinjilawi

2. Nematodes
 Ascaris lumbricoides.
 Hookworms:
A- Ancylostoma duodenale.
B- Necator americanus.
 Strongyloides stercoralis

3. Ascaris lumbricoides
 Common name: Roundworm.
 Habitat: Small intestine.
 Definitive host: Human.
 Route of infection:Hands carry infective ova
from soil contaminated with human excreta,
vegetables, dust, …etc.
 No Intermediate host.
 Infective stage: Eggs.
 Diagnostic stage: Eggs in Stool.
 Disease: Ascariasis.

4. Ascaris lumbricoides life cycle1

5. Ascaris lumbricoides life cycle2

6. Ascaris lumbricoides life cycle3

7. Ascaris lumbricoides
 Male: 150-200 x 2-4 mm
Curved tail. Shorter than female.
 Female: 200-350 x 4-6 mm.
 Habitat: Small intestine.
 Head of adult to show arrangement of
the three lips.( SEM;above.LM; C.S.
below.)

8. Ascaris lumbricoides Eggs
 Above-central: Thick mammillated albuminous
material, thick chitin shell, embryo inside.
 Above-right: Decorticated egg; only thick chitin
shell. Unembryonated.
 Above-left: Unfertilized egg; unequally distributed
mammillated albuminous layer,Unembryonated.
 Normal: Corticated,Unembryonated.

9. C.S. in Female of A. Lumbricoides
 Cu: Cuticle of skin.
 Lc: Dorsal nerve cord.
 Ms: Muscular layer.
 Od: Oviduct of ovary.
 Uterus filled with
eggs.

10. Ancylostoma duodenale
 Common name: Old world hookworm.
 Habitat: Small intestine.
 Definitive host: Human.
 Route of infection: Filariform larvae penetrate the skin
of human.
 No Intermediate host.
 Infective stage: Third stage larvae ( filariform).
 Diagnostic stage: Eggs in Stool.
 Disease: Hookworm infection, Ancylostomiasis.
 Geographic Distribution: Southern Europe, North parts
of Africa, China, India, and Japan.

11. Ancylostoma duodenale
life cycle

12. Hookworm life cycle

13. Ancylostoma duodenale
 Above-right: Egg; 60 x 40 um, thin-smooth-hyaline
shell, 4-8 cell cleavage (Unembryonated).
 Above-central: Ancylostoma feeding,C.S. in small
intestine.
 Above-left: SEM shows Ancylostoma head; Buccal
capsule with 2 pairs of teeth.

14. Necator americanus
 Common name: New world hookworm.
 Habitat: Small intestine.
 Definitive host: Human.
 Route of infection: Filariform larvae penetrate the
skin of human.
 No Intermediate host.
 Infective stage: Third stage larvae ( filariform).
 Diagnostic stage: Eggs in Stool.
 Disease: Hookworm infection, Ancylostomiasis.
 Geographic Distribution: Western hemisphere,
central and south Africa, south Asia, south pacific,
and India.

15. Necator americanus
 Above : Buccal capsule with
one pair of cutting plate.
 Below: Egg (70 x 38 um)
similar to A. duodenale;
Thin hyaline egg shell, 4-8
cell cleavage
(Unembryonated).
Life cycle similar to
A. duodenale

16. Hookworm Eggs

17. Necator americanus life cycle

18. Hookworm Rhabditiform larva
 Immature: 270 x 15
um, Mature: 540 x 700
um.
 Long buccal cavity
 small genital
primordium.

19. Hookworm Filariform larvae
 700 um
 Long buccal cavity.
 Small genital
primordium.
 Long esophagus.
 Pointed tail ( below)
Infective stage

20. Strongyloides stercoralis
 Common name: Thread worm
 Habitat: Small intestine.
 Definitive host: Human.
 Route of infection: Filariform larvae penetrate the
skin of human.
 No Intermediate host.
 Infective stage: Third stage larvae ( filariform).
 Diagnostic stage: First stage larvae(Rhabditiform)
in feces.
 Disease: Strongyloidiasis.

21. Strongyloides stercoralis life
cycle1

22. Strongyloides stercoralis life cycle2

23. Strongyloides stercoralis Rhabditiform larvae
 220 x 15 um.
 Short buccal cavity.
 Prominent genital primordium
( black arrow).
Diagnostic stage

24. Strongyloides stercoralis Filariform larvae
posterior part
 Filariform larva with
notched tail.
 |Infective stage
 600 x 20 um.

25. Comparison between hookworm and
Strongyloides stercoralis
Hookworm Strongyloides
stercoralis
Rhabditiform Long buccal Short buccal
larvae cavity, small cavity, prominent
genital genital
primordium primordium
Filariform Larvae Pointed tail, Short ,Notched tail
esophagus Long esophagus
Egg Thin shell,4-8 cell Thin shell,4-8 cell
cleavage cleavage

26. Comparison between hookworm and
Strongyloides stercoralis