introduction to Nematode and Ascaris lumbricodies

University of Duhok
College of Health Sciences
Dep. of Medical Laboratories
Parasitology Theory
3rd stage
Lecture 9
Dr.: Shameeran S. Ismael
BVM & S, M.Sc Medical Microbiology(Parasitology),
PhD Molecular Parasitology
Dr. Shameeran S. Bamarni
parasitology,2021, Medical Laboratory

Class Nematoda

General Features
• Elongated, cylindrical, smooth, unsegmented, flesh-
colored bodies.
• Sex: is separated; the female is usually larger than the
male
• Body is usually tapered to a pointed posterior end, and
to a rounded anterior end.
• The body is covered by cuticle

Female
Male

•Cuticle is secreted by underlying hypodermis, which project
into the body cavity forming two lateral cord carry the
excretory canals, and a dorsal and ventral cord carrying the
nerves.
Cuticle may be modified to form various structures:
1- Leaf crowns consisting of rows of papillae occurring
as fingers round the rim of the buccal capsule
(internal and external leaf crwon)
2- Cephalic vesicle
3- Cervical vesicle

4-Cervical ala
5- Cervical papillae
6. Cervical notch
7- Copulatory bursa in some species of male of nematodes,
which embrase the female during copulation. Which is
supported by bursal rays

• The muscle cells, arranged longitudinally lie between
hypoderms and the body cavity.
• Locomotion is effected by undulating wave of muscle
contraction and relaxation.
• They absorb oxygen through their skin in a process
known as diffusion.
Cross section of adult nematodes

• They have complete digestive system with mouth,
oesophagus, midgut and end with anus in female,
while in cloaca in male, because the cloaca is the
common opening for both digestive sys. and genital
system.
The type of mouth:
1.The mouth of many nematodes is a simple opening
which may surrounded by two or three lips and leads
directly into the oesophagus.
2- Large and open into a buccal capsule, which may be
contain teeth or cutting plate.

• Oesophagus: is usually muscular and pumps food into the
intestine. There are different shape of esophagus:
• Filariform: simple and slightly thickened posteriorly, as in
bursated nematodes
• Bulb-shaped: with a large posterior swelling, as in the ascaridoids
• Duoble-bulb-shaped
• Muscular-glandular: which is muscular anteriorly glandular
posteriorly)
• Trichuroid: has a capillary form, passing through a single column
of cells
• Rhabditiform: with slight anterior and posterior swellings

Types of oesophagus

• Intestine is a tube (enclosed by a single layer of cells)
Reproductive systems:
• Female reproductive sys.: ovary, oviduct and uterus,
ending in a common short vagina which opens at the
vulva.
• Female may be oviparous, viviparous or ovoviviparous

Male reproductive sys.
• Consist of a single continuous testis and a vas
deferens terminating in an ejaculatory duct.
• Spicules are chitinous organ which are usually
paired, which are inserted in the female genital
opening during copulation.
• Gubernaculum, also chitinous, which acts as a
guide for the spicules.

• The nematodes have direct life cycle, Nematodes have
a relatively simple basic life cycle consisting of an egg
stage, four larval or juvenile stages, and an adult stage
Infections is transmitted by:
1) Ingestion of eggs (Ascaris lumbricoides )
2) Penetration of larvae through surfaces (Hookworm)
3) Insect bite (Filaria)
4) Ingestion of encysted larvae (Trichnella spiralis)

Development of eggs and free living larvae
Eggs pass with feces and hatch in 24 hours to
rhabditiform L1. In successive molts, rhabitiform L1
and L2, which feed on micro-organisms, develop to
filariform infective L3. L3 do not feed (they live on
reserves) and are protected from adverse environments
by a sheath, the retained cuticle of the L2.

• Filariform larvae (L4): - the 3rd or infective stage; Long,
thread-like; Designed for penetration.
• Rhabditiform larvae (L1 and L2): - characterized by
the presence of a muscular esophagus and bulbular
pharynx. The worms leaving the egg are termed
“rhabditiform” larvae.

Ascaris lumbricoides
 Ascaris lumbricoides is the largest nematode
(roundworm) parasitizing the human intestine.
 Ascaris lumbricoides is an intestinal worm found in
the small intestine of man.
 They are more common in children then in adult.

Keys
Kingdome: Animalia
Phylum: Nematohelminthes
Class: Nematoda
Order: Ascaridida
Super family: Ascarididea
Family: Ascarididae
Genus: Ascaris
Species: lumbricoides

Common name: Giant Intestinal round worms
Final host: Human
Site of infection: Small intestine
Infective stage: Fertilized eggs
Life cycle: Direct
Disease: Ascariasis

Morphology
1.Adult:
• Large, tapering at both ends in female and curved
posteriorly in male
• The female are slightly larger than males
• When freshly passed in the stool, the adult worm is
light cream or pink in color

Adult worm
Female worm Male worm

Ascaris lumbricoieds lips
•The mouth opens at the anterior end & they possesses 3
finely toothed lips one dorsal & two ventral
•Each lips possesses a pair of sensory papillae on its lateral
margin

Dr. Shameeran S. Bamarni parasitology,2021, Medical Laboratory
2. Egg:
• There are two types of eggs:
1.Fertilized eggs
2.Unfertilized eggs

1. Fertilized Eggs
• Round or oval in shape
• Surrounded by a thick smooth translucent shell
with an outer albuminous coat
• The internal shell is smooth, thick and colorless

2.Unfertilized egg:
-Longer and slender than a fertilized egg. The chitinous
layer and albuminous coat are thinner without
ascaroside and fertilizing membrane. The content is
made of many refractable granules various in size.

Life cycle
• Life cycle direct
• Eggs (fertilized & unfertilized eggs pass with
feces)
• Final host is infected by ingestion of
contaminated food, raw vegetable & drinking of
water with fertilized eggs
• After ingestion of fertilized eggs, the eggs
hatched in the duodenum & L1 released
• The L1 burrow their way through the mucous
membrane of the small intestine & are carried by
portal circulation to the liver

• Finally they migrate from liver & via the right heart
enter the pulmonary circulation
• In lungs L1 become L2 & L3,& L3 reach the alveoli
to bronchi & trachea , larynx& pharynx, then are
swallowed & return t the small intestine & L3 molt to
L4 & L5 & adult

Pathogenesis& clinical signs
There are two phases in Ascariasis:
1. The intestinal phase of the adults:
-The presence of a few adult worms in the lumen of the
small intestine usually produces no symptoms, but
may give rise to vague abdominal pains or intermittent
colic

2. The blood-lung migration phase of the larvae:
During the migration through the lungs, the larvae may cause
a pneumonia. The symptoms of the pneumonia are low
fever, cough, blood-tinged sputum.

Diagnosis:
• The diagnosis depends on the Identify worm or egg:-
• The Stool examination : for seeing the adult worm or
egg .
• The sputum examination :for seeing larva during
migration in the lung.
• Eosinophilia as indicator on parasitic infection

Prevention:
• Keeping good sanitation conditions is the only way to
prevent the infection of Ascaris.
• Good washing of vegetable
• Finger nails should be regularly cut to avoid the
collection of dirt and eggs below them.
• Hands should be properly washed with some
antiseptic soap before touching edibles or eating

Treatment:
Several anthelmintics drugs of choice:
• Pyrantel pamoate
• Mebendozle
• Piperazine citrate

introduction to Nematode and Ascaris lumbricodies

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