Ascaris lumbricoidesAscaris lumbricoides

Suan Lui TeohSuan Lui Teoh

Danh VoongDanh Voong

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)

GeographyGeography

WorldwideWorldwide High prevalence in underdeveloped High prevalence in underdeveloped

countries that have poor sanitation countries that have poor sanitation (parts of Asia, South America and (parts of Asia, South America and Africa)Africa)

Occurs during rainy months, tropical Occurs during rainy months, tropical and subtropical countriesand subtropical countries

Even occurs in rural areas in the Even occurs in rural areas in the United StatesUnited States

HostHost

Definitive host : Humans or pigsDefinitive host : Humans or pigs

Intermediate Host : -none-Intermediate Host : -none-

Modes of transmissionModes of transmission Occurs mainly via ingestion of water or food (raw Occurs mainly via ingestion of water or food (raw

vegetables or fruit in particular) contaminated with A. vegetables or fruit in particular) contaminated with A. lumbricoides eggs.lumbricoides eggs.

Occasionally inhalation of contaminated dustOccasionally inhalation of contaminated dust

Children playing in contaminated soil may acquire the Children playing in contaminated soil may acquire the parasite from their handsparasite from their hands

Enhanced by the fact that individuals can be Enhanced by the fact that individuals can be asymptomatically infected and continues to shed eggs for asymptomatically infected and continues to shed eggs for yearsyears

Prior infection does not confer protective immunityPrior infection does not confer protective immunity

MorphologyMorphology

Fertile eggFertile egg mammillated mammillated thick external layer thick external layer unembryonated unembryonated measures 55-75 measures 55-75

mm by 35-50 mm mm by 35-50 mm

Morphology Cont.Morphology Cont.

Infertile eggInfertile egg elongated and larger elongated and larger

than fertile egg than fertile egg thin shelled thin shelled shell ranges from shell ranges from

irregular irregular mammillations to a mammillations to a relatively smooth layer relatively smooth layer completely lacking completely lacking mammillations mammillations

measures between 85-measures between 85-95 mm by 43-47 mm 95 mm by 43-47 mm

Morphology Cont.Morphology Cont.

InfertileInfertile FertileFertile

EggEgg

Can survive for prolonged periods as long as Can survive for prolonged periods as long as warm, shade, moist conditions are available warm, shade, moist conditions are available and can live up to 10 yearsand can live up to 10 yearsEggs are resistant to unusual methods of Eggs are resistant to unusual methods of chemical water purificationchemical water purificationEggs are removed by filtration and killed by Eggs are removed by filtration and killed by boiling.boiling.Developing larvae are destroyed by sunlight Developing larvae are destroyed by sunlight and desiccationand desiccation

Morphology Cont.Morphology Cont.

Adult worm:Adult worm: tapered ends; length tapered ends; length

15 to 35 cm 15 to 35 cm Female are larger in Female are larger in

size and have a size and have a genital girdle genital girdle

The 3 prominent “lips”The 3 prominent “lips”

Life CycleLife Cycle

Life Cycle Cont.Life Cycle Cont.1.1. Females lay eggs in small intestine and eggs Females lay eggs in small intestine and eggs

are passed out through feces.are 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 Ingestion of raw foods, fruits or vege contaminated with eggs will cause infectioncontaminated with eggs will cause infection

5.5. Eggs hatch in small intestine, releases L2 Eggs hatch in small intestine, releases L2 rhabditiform larvaerhabditiform larvae

6.6. L2 penetrate intestinal wall, enter portal blood L2 penetrate intestinal wall, enter portal blood stream, migrate to liver, heart and lungs in 1-7 stream, migrate to liver, heart and lungs in 1-7 daysdays

7.7. Moults twice to become L4 larvaeMoults twice to become L4 larvae

Cont.Cont.8.8. Borrow out of blood vessels and enter Borrow out of blood vessels and enter

bronchiolsbronchiols

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 Enter throat and swallowed to end up in the small intestinesmall intestine

11.11. Mature and mate, where they complete their Mature and mate, where they complete their life cyclelife cycle

Food HabitsFood Habits Feeds on semi-digested contents in Feeds on semi-digested contents in

the gutthe gut

Evidence show that they can bite the Evidence show that they can bite the intestinal mucus membrane and feed intestinal mucus membrane and feed on blood and tissue fluidson blood and tissue fluids

SymptomsSymptomsSymptoms associated with larvae migrationSymptoms associated with larvae migration

Migration of larvae in lungs may cause Migration of larvae in lungs may cause hemorrhagic/ eosinophilic pneumonia, cough hemorrhagic/ eosinophilic pneumonia, cough (Loeffler's Syndrome)(Loeffler's Syndrome)

Breathing difficulties and feverBreathing difficulties and fever

Complications caused by parasite proteins that Complications caused by parasite proteins that are highly allergenic - asthmatic attacks, are highly allergenic - asthmatic attacks, pulmonary infiltration and urticaria (hives)pulmonary infiltration and urticaria (hives)

Symptoms Cont.Symptoms Cont.Symptoms associated with adult parasite in Symptoms associated with adult parasite in

the intestinethe intestine

Usually asymptomaticUsually asymptomatic

Abdominal discomfort, nausea in mild casesAbdominal discomfort, nausea in mild cases

Malnutrition in host especially children in severe Malnutrition in host especially children in severe casescases

Sometimes fatality may occur when mass of Sometimes fatality may occur when mass of worm blocks the intestineworm blocks the intestine

HOST IMMUNE RESPONSEHOST IMMUNE RESPONSE

Innate Immune ResponseInnate Immune Response Macrophage, neutrophils and most Macrophage, neutrophils and most

importantly eosinophilsimportantly eosinophils The worms would be coated with IgG or IgE The worms would be coated with IgG or IgE

which would increase the release of which would increase the release of eosinophil granules on the worm’s surfaceeosinophil granules on the worm’s surface

Adaptive Immune ResponseAdaptive Immune Response General consensus is a Th2 immune General consensus is a Th2 immune

response with high IL-4 production, high response with high IL-4 production, high levels of IgE, eosinophilia and mastocytosislevels of IgE, eosinophilia and mastocytosis

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 : eosinophilia can be found, particularly during larval migration through the lungslarval migration through the lungs

ImagingImaging: In heavily infested individuals, particularly children, : In heavily infested individuals, particularly children, large collections of worms may be detectable on plain film of the large collections of worms may be detectable on plain film of the abdomen.abdomen.

UltrasoundUltrasound: ultrasound exams can help to diagnose : ultrasound exams can help to diagnose hepatobiliary or pancreatic ascariasis. Single worms, bundles of hepatobiliary or pancreatic ascariasis. Single worms, bundles of worms, or pseudotumor-like appearance, individual body worms, or pseudotumor-like appearance, individual body segments of worms may be seen.segments of worms may be seen.

Endoscopic Retrograde Cholangiopancreatography Endoscopic Retrograde Cholangiopancreatography (ERCP) :(ERCP) :A duodenoscope with a snare to extract the worm out of the A duodenoscope with a snare to extract the worm out of the patientpatient

TreatmentTreatment MebendazoleMebendazole AlbendazoleAlbendazole Pyrantel pamoatePyrantel pamoate IvermectinIvermectin Piperazine citratePiperazine citrate LevamisoleLevamisole

PreventionPrevention

Prevention of reinfection poses a substantial Prevention of reinfection poses a substantial problem since this parasite is abundant in soil – problem since this parasite is abundant in soil – therefore good sanitation is needed to prevent therefore good sanitation is needed to prevent fecal contamination of soil fecal contamination of soil

Limit using human feces as fertilizerLimit using human feces as fertilizer Treatment can be done on contaminated soil Treatment can be done on contaminated soil

although it is not highly advisedalthough it is 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 transmission in community but can cause reinfectionreinfection

Some cool picturesSome cool pictures

How many people in the world How many people in the world are estimated to be infected are estimated to be infected

with A. lumbricoides ?with A. lumbricoides ?

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

Name 2 modes of Name 2 modes of transmission?transmission?

What morphological difference What morphological difference can be seen in fertile and can be seen in fertile and

infertile eggs?infertile eggs?

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

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

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