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