Nematodes
• Female or male
• Cylindrical
• 4 tubes
• Digestive system, genital system, excretory system, nervous system.
The Nematodes: (Round worms)
- They are small round elongated worms, non-segmented, with a body cavity,
have separate sexes.
• Divide into:
• intestinal nematodes and tissue nematodes
Ascaris lumbricoides
Infect by eggs that are strongly resistant to desiccation &
environmental conditions.
• Eggs are 75x40 µm, with a thick mamillated brownish shell.
• Freshly passed eggs in feces are not infective, they require 2-3
weeks to develop to be embryonated (contain larva).
Ascaris lumbricoides
• Largest nematodes in the human small intestine
• Small intestine ( 85% in the jejunim,15 in the ilium)
• ADULT:
• Large cylindrical with tapering end
• Sex are separate
• Flesh color
• Mouth at the interior end with 3 toothed lips
• Male
• 15-30cm * 2-4mm
• Posterior end curved to form hook
• Femal
• 20-40cm *3-6mm
• Posterior end straight
• Distinct groove is present at valvar opening
• 2,00,000 eggs per day
• 2 type of eggs
• Fertilized egg
• Embyronated unsegmented ovum
• Develop into the infective form
• Round oval
• Unfertilized
• Atrophied ovum
• Elliptial in shape
• larger
Unfertilized egg
Elongated
Thin shelled
Disorganized internal content
Ascaris lumbricoides
Unfertilized egg
Elongated
Thin shelled
Disorganized internal
content
Egg containing a larva-
infective if ingested
Adult worms
Hookworms
Ancylostoa duodenale & Necator Americanus:
- Small nematode 1cm x 1mm, adult worms found in small intestine get
hold by teeth resulting in hemorrhages.
Adult male and female
worms of A. duodenale
Egg of A. duodenale in faecal smear
Trichuris trichiura• Whip-worm, adults 3-7cm, live in caecum & colon of man.
• Eggs are barrel-shaped, 50x25 µm with a thick brown shell and a
mucoid plug at each pole. They are passed in feces to complete
development in soil as in Ascaris. This emryonated egg is the infective
stage.
Adults of T. trichiura Egg of T. trichiura
Enterobius vermicularis (Pinworm)
Small nematode, a common parasite among children, it is unique in that
eggs are viable shortly after being laid directly on the perianal skin. They
can be accidentally ingested, or passed on fingers, clothing or fecal flecks
to others.
Itching around the anal or vaginal areas are the most common pinworm
symptoms. Suspect a pinworm infection if the child shows night time
itching in these areas.
Pinworm EggsAn adult pinworm An adult pinworm
Life Cycle Diagram of Pinworms
Tissue nematodes
• Skin lymph vessel
• vectors