2. Introduction
a common cream colored roundworm that
is parasitic in the intestines of humans
Most common helminthic human infection
Largest nematode to infect the human
intestine
An estimated 1 billion people are infected
(1 out of 4 people in the world)
3. Geography
Worldwide
High prevalence in underdeveloped
countries that have poor sanitation (parts
of Asia, South America and Africa)
Occurs during rainy months, tropical and
subtropical countries
Even occurs in rural areas in the United
States
5. Modes of transmission
Occurs mainly via ingestion of water or food (raw vegetables or fruit
in particular) contaminated with A. lumbricoides eggs.
Occasionally inhalation of contaminated dust
Children playing in contaminated soil may acquire the parasite from
their hands
Enhanced by the fact that individuals can be asymptomatically
infected and continues to shed eggs for years
Prior infection does not confer protective immunity
7. Morphology Cont.
Infertile egg
elongated and larger than
fertile egg
thin shelled
shell ranges from
irregular mammillations to
a relatively smooth layer
completely lacking
mammillations
measures between 85-95
mm by 43-47 mm
9. Egg
Can survive for prolonged periods as long as
warm, shade, moist conditions are available and
can live up to 10 years
Eggs are resistant to unusual methods of chemical
water purification
Eggs are removed by filtration and killed by boiling.
Developing larvae are destroyed by sunlight and
desiccation
13. Life Cycle Cont.
1. Females lay eggs in small intestine and eggs are
passed out through feces.
2. After 14 days, L1 larvae develops in eggs
3. L2 larvae develops after one week
4. Ingestion of raw foods, fruits or vege contaminated
with eggs will cause infection
5. Eggs hatch in small intestine, releases L2 rhabditiform
larvae
6. L2 penetrate intestinal wall, enter portal blood stream,
migrate to liver, heart and lungs in 1-7 days
7. Moults twice to become L4 larvae
14. Cont.
8. Borrow out of blood vessels and enter bronchiols
9. Migrate through the lungs into the trachea
10. Enter throat and swallowed to end up in the small
intestine
11. Mature and mate, where they complete their life cycle
15.
16. Food Habits
Feeds on semi-digested contents in the
gut
Evidence show that they can bite the
intestinal mucus membrane and feed on
blood and tissue fluids
17. Symptoms
Symptoms associated with larvae migration
Migration of larvae in lungs may cause hemorrhagic/
eosinophilic pneumonia, cough (Loeffler's Syndrome)
Breathing difficulties and fever
Complications caused by parasite proteins that are
highly allergenic - asthmatic attacks, pulmonary
infiltration and urticaria (hives)
18. Symptoms Cont.
Symptoms associated with adult parasite in the
intestine
Usually asymptomatic
Abdominal discomfort, nausea in mild cases
Malnutrition in host especially children in severe cases
Sometimes fatality may occur when mass of worm
blocks the intestine
19. HOST IMMUNE RESPONSE
Innate Immune Response
Macrophage, neutrophils and most importantly
eosinophils
The worms would be coated with IgG or IgE
which would increase the release of eosinophil
granules on the worm’s surface
Adaptive Immune Response
General consensus is a Th2 immune response
with high IL-4 production, high levels of IgE,
eosinophilia and mastocytosis
20. Diagnosis
Stool microscopy :eggs may be seen on direct examination of
feces.
Eosinophilia : eosinophilia can be found, particularly during larval
migration through the lungs
Imaging : In heavily infested individuals, particularly children, large
collections of worms may be detectable on plain film of the
abdomen.
Ultrasound : ultrasound exams can help to diagnose hepatobiliary
or pancreatic ascariasis. Single worms, bundles of worms, or
pseudotumor-like appearance, individual body segments of worms
may be seen.
Endoscopic Retrograde Cholangiopancreatography
(ERCP) :
A duodenoscope with a snare to extract the worm out of the patient
22. Prevention
Prevention of reinfection poses a substantial problem
since this parasite is abundant in soil – therefore good
sanitation is needed to prevent fecal contamination of
soil
Limit using human feces as fertilizer
Treatment can be done on contaminated soil although it
is not highly advised
Mass treatments of children with single doses of
mebendazole or albendazole – helps reduce
transmission in community but can cause reinfection