nematodes

NEMATODES (ROUND WORM)
All important human parasites of the phylum nemathelminthes belong to the class nematode.
Classification
Phylum: nemathelminthes
Class: nematode
The nematodes species may divided in to 2 groups :
1- Intestinal species:
• Entrobius vermicularis
• Tricuris trichura
• Ascaris lumbricoides
• Ancylostoma dudenale
• Strongyloides stercoralis
2- Intestinal –tissue species
• Trichinella spiralis
• Dracuncuus medinensis
General characters of nematodes:
1- They are elongated, cylindrical, unsegmented worms.
2- The male is generally smaller than female.
3- The sexes are separate (diecious)
4- The adults are equipped with complete digestive and reproductive systems.
5- Excretory and nervous systems are rudimentary.
6- Circulatory system is absent and the body wall consist of an outer layer cuticle and inner layer of longitudinal muscle.
Entrobius vermicularis(pin worm)
Common name :thread worm, pin worm, seat worm.
Habitat: the adult worm live in caecum , vermiform appendix and adjacent portion of ascending colon .
Disease: Entrobiasis or pin worm infection
Morphology:
Adult worms: these are small, white, spindle-shaped and resemble short pieces of thread. at anterior end , both male and female worms possess a pair of wing-like extension known as cervical. The male measures 2-4 mm in length and 0.1-0.2 mm in breadth. The posterior one third of the body is curved. The female is longer, 8.12mm in length and 0.3-0.5mm in width. Its posterior one third is straight and drawn out into a thin pointed pin-like tail.
Eggs : the typical E.vermicularis egg measures 48-60 µm in length by 20-35 µm in width. The somewhat oval egg is characteristically flattened on one side. The egg consists of a developing larva surrounded by a conspicuous double-layered , thick-wall . colorless shell.
Infective stage: by ingestion of eggs containing larvae.
Mode of infection:
• by direct infection from a patient (fecal- oral rote) .
• Aerosol inhalation from contaminated sheets and dust.
• Autoinfection: the eggs are infective as soon as they are passed by the female worm. If the hands of the patient get contaminated with these eggs, the patient infect himself again.

Life cycle: Adult worm live in large intestine .After fertilization , the male dies and the female moves out through the anus to glue its eggs on the peri-anal skin . this takes place by night. The egg contain larva . when the eggs are swallowed , they hatch in the small intestine and the larvae migrate to the large intestine to become adult.

Clinical symptoms:
The migration of the worms causes allergic reactions around the anus and during
night it causes nocturnal itching (pruritus ani) and enuresis. The worms may obstruct the appendix causing appendicitis.
Lab.diagnosis:
• Eggs in stool: Examination of the stool by direct smear to detect the egg: this is positive in about 5% of cases because the eggs are glued to the peri-anal skin.
• Peri-anal swab: The peri-anal region is swabbed with a piece of adhesive tape (cello tape) hold over a tongue depressor. The adhesive tape is placed on a glass slide and examined for eggs. The swab should be done in the early morning before bathing and defecation.