Ascaris lumbricoides

1. Ascaris lumbricoidesAscaris lumbricoides
Suan Lui TeohSuan Lui Teoh
Danh VoongDanh Voong

2. IntroductionIntroduction

a common cream colored roundworm that a common cream colored roundworm that
is parasitic in the intestines of humans is parasitic in the intestines of humans

Most common helminthic human infectionMost common helminthic human infection

Largest nematode to infect the human Largest nematode to infect the human
intestineintestine

An estimated 1 billion people are infected An estimated 1 billion people are infected
(1 out of 4 people in the world)(1 out of 4 people in the world)

3. GeographyGeography

WorldwideWorldwide

High prevalence in underdeveloped High prevalence in underdeveloped
countries that have poor sanitation (parts countries that have poor sanitation (parts
of Asia, South America and Africa)of Asia, South America and Africa)

Occurs during rainy months, tropical and Occurs during rainy months, tropical and
subtropical countriessubtropical countries

Even occurs in rural areas in the United Even occurs in rural areas in the United
StatesStates

4. HostHost

Definitive host : Humans or pigsDefinitive host : Humans or pigs

Intermediate Host : -none-Intermediate Host : -none-

5. Modes of transmissionModes of transmission

Occurs mainly via ingestion of water or food (raw vegetables or fruit Occurs mainly via ingestion of water or food (raw vegetables or fruit
in particular) contaminated with A. lumbricoides eggs.in particular) contaminated with A. lumbricoides eggs.

Occasionally inhalation of contaminated dustOccasionally inhalation of contaminated dust

Children playing in contaminated soil may acquire the parasite from Children playing in contaminated soil may acquire the parasite from
their handstheir hands

Enhanced by the fact that individuals can be asymptomatically Enhanced by the fact that individuals can be asymptomatically
infected and continues to shed eggs for yearsinfected and continues to shed eggs for years

Prior infection does not confer protective immunityPrior infection does not confer protective immunity

6. MorphologyMorphology
Fertile eggFertile egg

mammillated mammillated

thick external layer thick external layer

unembryonated unembryonated

measures 55-75 mm measures 55-75 mm
by 35-50 mm by 35-50 mm

7. Morphology Cont.Morphology Cont.
Infertile eggInfertile egg

elongated and larger than elongated and larger than
fertile egg fertile egg

thin shelled thin shelled

shell ranges from shell ranges from
irregular mammillations to irregular mammillations to
a relatively smooth layer a relatively smooth layer
completely lacking completely lacking
mammillations mammillations

measures between 85-95 measures between 85-95
mm by 43-47 mm mm by 43-47 mm

8. Morphology Cont.Morphology Cont.

InfertileInfertile

FertileFertile

9. EggEgg
Can survive for prolonged periods as long as Can survive for prolonged periods as long as
warm, shade, moist conditions are available and warm, shade, moist conditions are available and
can live up to 10 yearscan live up to 10 years
Eggs are resistant to unusual methods of chemical Eggs are resistant to unusual methods of chemical
water purificationwater purification
Eggs are removed by filtration and killed by boiling.Eggs are removed by filtration and killed by boiling.
Developing larvae are destroyed by sunlight and Developing larvae are destroyed by sunlight and
desiccationdesiccation

10. Morphology Cont.Morphology Cont.
Adult worm:Adult worm:

tapered ends; length 15 tapered ends; length 15
to 35 cm to 35 cm

Female are larger in size Female are larger in size
and have a genital girdle and have a genital girdle

11. The 3 prominent “lips”The 3 prominent “lips”

12. Life CycleLife Cycle

13. Life Cycle Cont.Life Cycle Cont.
1.1.Females lay eggs in small intestine and eggs are Females lay eggs in small intestine and eggs are
passed out through feces.passed out through feces.
2.2.After 14 days, L1 larvae develops in eggsAfter 14 days, L1 larvae develops in eggs
3.3.L2 larvae develops after one weekL2 larvae develops after one week
4.4.Ingestion of raw foods, fruits or vege contaminated Ingestion of raw foods, fruits or vege contaminated
with eggs will cause infectionwith eggs will cause infection
5.5.Eggs hatch in small intestine, releases L2 rhabditiform Eggs hatch in small intestine, releases L2 rhabditiform
larvaelarvae
6.6.L2 penetrate intestinal wall, enter portal blood stream, L2 penetrate intestinal wall, enter portal blood stream,
migrate to liver, heart and lungs in 1-7 daysmigrate to liver, heart and lungs in 1-7 days
7.7.Moults twice to become L4 larvaeMoults twice to become L4 larvae

14. Cont.Cont.
8.8.Borrow out of blood vessels and enter bronchiolsBorrow out of blood vessels and enter bronchiols
9.9.Migrate through the lungs into the tracheaMigrate through the lungs into the trachea
10.10.Enter throat and swallowed to end up in the small Enter throat and swallowed to end up in the small
intestineintestine
11.11.Mature and mate, where they complete their life cycleMature and mate, where they complete their life cycle

16. Food HabitsFood Habits

Feeds on semi-digested contents in the Feeds on semi-digested contents in the
gutgut

Evidence show that they can bite the Evidence show that they can bite the
intestinal mucus membrane and feed on intestinal mucus membrane and feed on
blood and tissue fluidsblood and tissue fluids

17. SymptomsSymptoms
Symptoms associated with larvae migrationSymptoms associated with larvae migration

Migration of larvae in lungs may cause hemorrhagic/ Migration of larvae in lungs may cause hemorrhagic/
eosinophilic pneumonia, cough (Loeffler's Syndrome)eosinophilic pneumonia, cough (Loeffler's Syndrome)

Breathing difficulties and feverBreathing difficulties and fever

Complications caused by parasite proteins that are Complications caused by parasite proteins that are
highly allergenic - asthmatic attacks, pulmonary highly allergenic - asthmatic attacks, pulmonary
infiltration and urticaria (hives)infiltration and urticaria (hives)

18. Symptoms Cont.Symptoms Cont.
Symptoms associated with adult parasite in the Symptoms associated with adult parasite in the
intestineintestine

Usually asymptomaticUsually asymptomatic

Abdominal discomfort, nausea in mild casesAbdominal discomfort, nausea in mild cases

Malnutrition in host especially children in severe casesMalnutrition in host especially children in severe cases

Sometimes fatality may occur when mass of worm Sometimes fatality may occur when mass of worm
blocks the intestineblocks the intestine

19. HOST IMMUNE RESPONSEHOST IMMUNE RESPONSE
Innate Immune ResponseInnate Immune Response

Macrophage, neutrophils and most importantly Macrophage, neutrophils and most importantly
eosinophilseosinophils

The worms would be coated with IgG or IgE The worms would be coated with IgG or IgE
which would increase the release of eosinophil which would increase the release of eosinophil
granules on the worm’s surfacegranules on the worm’s surface
Adaptive Immune ResponseAdaptive Immune Response

General consensus is a Th2 immune response General consensus is a Th2 immune response
with high IL-4 production, high levels of IgE, with high IL-4 production, high levels of IgE,
eosinophilia and mastocytosiseosinophilia and mastocytosis

20. DiagnosisDiagnosis

Stool microscopyStool microscopy :eggs may be seen on direct examination of :eggs may be seen on direct examination of
feces. feces.

EosinophiliaEosinophilia: eosinophilia can be found, particularly during larval : eosinophilia can be found, particularly during larval
migration through the lungsmigration through the lungs

ImagingImaging: In heavily infested individuals, particularly children, large : In heavily infested individuals, particularly children, large
collections of worms may be detectable on plain film of the collections of worms may be detectable on plain film of the
abdomen.abdomen.

UltrasoundUltrasound: ultrasound exams can help to diagnose hepatobiliary : ultrasound exams can help to diagnose hepatobiliary
or pancreatic ascariasis. Single worms, bundles of worms, or or pancreatic ascariasis. Single worms, bundles of worms, or
pseudotumor-like appearance, individual body segments of worms pseudotumor-like appearance, individual body segments of worms
may be seen.may be seen.

Endoscopic Retrograde Cholangiopancreatography Endoscopic Retrograde Cholangiopancreatography
(ERCP) :(ERCP) :
A duodenoscope with a snare to extract the worm out of the patientA duodenoscope with a snare to extract the worm out of the patient

21. TreatmentTreatment

MebendazoleMebendazole

AlbendazoleAlbendazole

Pyrantel pamoatePyrantel pamoate

IvermectinIvermectin

Piperazine citratePiperazine citrate

LevamisoleLevamisole

22. PreventionPrevention

Prevention of reinfection poses a substantial problem Prevention of reinfection poses a substantial problem
since this parasite is abundant in soil – therefore good since this parasite is abundant in soil – therefore good
sanitation is needed to prevent fecal contamination of sanitation is needed to prevent fecal contamination of
soil soil

Limit using human feces as fertilizerLimit using human feces as fertilizer

Treatment can be done on contaminated soil although it Treatment can be done on contaminated soil although it
is not highly advisedis not highly advised

Mass treatments of children with single doses of Mass treatments of children with single doses of
mebendazole or albendazole – helps reduce mebendazole or albendazole – helps reduce
transmission in community but can cause reinfectiontransmission in community but can cause reinfection

23. Some cool picturesSome cool pictures

26. How many people in the world are How many people in the world are
estimated to be infected with A. estimated to be infected with A.
lumbricoides ?lumbricoides ?

27. Who are the definitive host/s of this Who are the definitive host/s of this
parasite?parasite?

28. Name 2 modes of transmission?Name 2 modes of transmission?

29. What morphological difference can What morphological difference can
be seen in fertile and infertile eggs?be seen in fertile and infertile eggs?

30. Name the symptom caused by Name the symptom caused by
larvae migration in the lungs.larvae migration in the lungs.

31. What is the drug of choice for this What is the drug of choice for this
parasite?parasite?

32. What are some of the methods of What are some of the methods of
prevention?prevention?