Ascaris Lumbricoides

Ascaris lumbricoides
Lecture by: Maha Gamal Eldein Ali

Introduction
• Ascaris lumbricoides is the largest intestinal nematode found in human
• Inhabit human small intestine.
• Causing the disease known as Ascariasis.
• It is soil transmitted infection
• It is most common in children ( young children , school and preschool
children)
2

Geographical distribution:
• About 1 billion people are infected with A. lumbricoides
• The infection occurs throughout most of the world; Africa countries,
Philippines, India, Middle East, Europe, Central & South America,
Indonesia
• The infection is spread is more common in villages & Rural
communities.
3

Ascaris infection is more common in
discussion))rural areas
4

Morphology (the worm)
Shape: round or cylindrical,
tapered at both ends
Color: pink- creamy
Size:
Male=15 -31cm in length x 2-4
mm in diameter
Female=20-35 cm x 3-6 mm, it
may reach up to 46 cm in length.
6

Morphology (worm)
• Sex is separate
• Males are smaller than the female worms
The male: is curved at the posterior end.
8

Ascaris female are oviparous, produce 2 types of eggs
1- fertilized eggs
• Shape: round to oval
• Size: 60-75 x 50-60 µm
• Color: golden brown
• Content: unembryonated contain a
round compact mass of granules
Shell: thick composed of 3 layers;
inner vitelline, middle transparent
layer, outer irregular albuminoid
layer.
10

2- unfertilized eggs
• Shape: oval elongate
• Size: 90 x45µm
• Color: brown
• Content: diffuse mass of large
refractile granules
• Shell: thin composed of 3 layers;
inner vitelline, middle
transparent layer, outer irregular
albuminoid layer.
12

At times both eggs (fertilized or unfertilized) has no outer albuminoid
layer: so it is known as decorticated eggs.
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Development of Ascaris eggs
14
1cell stage 2cell stage morula
L1 L2 L2 – L5

How man become infected?
• Man become infected by ingestion of infective Ascaris eggs; contain
second stage larva L2.
• The larva hatch in the small intestine, and penetrate the wall of the
intestine enter the portal circulation, carried to heart, then to lungs
(Heart lung migration)
• Within 9-15 days In lungs the larva develop to L3, which migrate up
through the bronchial tree, reach the throat then swallowed and
enter the intestine.
15

• In the intestine the Ascaris larva grow into L4 then L5 which
then mature into worm within 2-3 month.
• The mature female will be fertilized by the male worms
(mating).
• Each worm uteri may contain up to 27 million eggs at a
time, but it produce about 200,000 eggs /day which deposit
in feces.
.
16

How life cycle continue?
The life cycle continue when the eggs reach the soil
• when infected human defecate in soil the eggs will reach the
soil.
2- under certain soil conditions; Oxygen, Shad, Moisture,
Temperature 22-30 ᵒC, the fertilized eggs develop into infective
eggs.
3-Ingestion those of infective eggs by other (contamination of
hands, foods, drinks with soil contain the eggs)
• While the infertile eggs don't develop; has no role in the life cycle
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Factor help spreading of Ascariasis
• The worm produce large numbers of eggs
• The eggs resistant to strong chemicals, desiccation, and low
temperatures.
• The eggs can remain viable in the soil for several months or even
years.
19

Pathology & Symptomatology
• Lung phase:
The early phase due to larva development in lungs, cause
Ascaris pneumonitis coupled with asthma like symptoms
(loffler’s syndrome)
Usually the symptoms last for 14 days and disappear
spontaneously.
usually the severity of symptoms depends on the number
of larvae.
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Intestinal phase:
Due to presence
of Ascaris worm in the intestine associate with:
• Colic pain
• Loss of appetite
• Fullness
• Impaired carbohydrate absorption
• Impaired fat absorption (steatorrhea)
• Long term infection associate with malnutrition & impaired growth in
children.
• Large number of worm cause obstruction of bowel.
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Obstruction of bowel by Ascaris worms
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Extra intestinal effect of the worm:
Due to migration of worm from intestine to other sites
• obstructive jaundice due to obstruction of bile duct by the worms
• liver abscess (hepatic Ascariasis) when worm force its body through
gallbladder and inter the liver.
• The worms may inter the liver veins then carried to (brain, heart,
lungs) causing serious complications.
• Pancreatitis when the worms migrate up enter and block the
pancreatic duct .
• Appendicitis when the worm migrate down enter and block the
appendix .
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Laboratory Diagnosis
1- what is /are suitable sample/s?
2- what is are suitable diagnostic test/s or technique/s?
3- what is/are the diagnostic stage/s?
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Summary:
• Ascaris lumbricoides worms inhabit human small intestine
• The worm release large number eggs(200,000 egg/each worm daily
which deposit in feces.
• Eggs in stool found as (fertilized & unfertilized) they may be
decorticated
• The adult worm may pass through the anus, mouth, or nose specially
in febrile illness( fever).
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Ascaris worm coming through anus, nose and
mouth,
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1- Stool is the best sample to diagnose Ascariasis
2- suitable diagnostic technique:
Eggs of A. lumbricoides can be easily found in direct wet
mount with saline because the worm produce large
number of eggs.
3- diagnostic stages:
A- In stool eggs ( fertilized/ unfertilized/ decorticated)
B-adult worm if come out through mouth, nose, or anus
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How to identify Ascaris worms??
• The worm should be washed with water
• Then fixed with hot 10% formalin for 10 minutes
• Remove the worm from the fixative and measure the
length of the worm
• Use hand lens to see the 3lips
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Treatment
Several anthelmintics drugs of choice:
• Pyrantel pamoate
• Mebendozle
• Piperazine citrate
Prognosis
• The prognosis is excellent (intestinal)
• In surgical conditions( extraintestinal) it depends on the
location
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Epidemiology
Ascaris lumbricoides one of the highly spread helminthes
infection Factors helps disease spreading
• Defecation if infective persons in soil
• Favorable condition of soil which is required for egg
development.
• The worm produce very large number of eggs
• Ability of eggs to resist the unfavorable conditions.
• Coprophagous animals; young dogs & pigs ( eat fresh human
feces) and transport the eggs to different sites.
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Prevention & control
why the soil become contaminated??
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• construction of feces where people
need to prevent defecation in soil.
• Prevent use of human feces as soil
fertilizer (night soil)
• If night soil used should be treated
( by chemical or physical methods)
to destroy the eggs
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• Mass treatment for all age
groups once or twice a year
(specially in rural communities)
• Washing hands
• Washing vegetables & fruits
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Ascaris Lumbricoides

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