Ascaris lumbricoidesBeth Wozney

The largest nematode to infect the human

intestine..

Taxonomy

Kingdom: Animalia

Phylum: Nematoda

Class: Rhabditea

Order: Ascaridida

Family Ascarididae

Genus: Ascaris

Species: lumbricoides

Geographic Distribution

Up to ONE BILLION people wolrdwide are infected.

Both tropical and temperate areasMore common in tropical and subtropical

In the United States?South Eastern states

Children are most

commonly infected

Morphology

15-35 cm long and the diameter of a lead pencil

Female: straight posteriorMale: curved posterior (button-hook tail)

Morphology

Both male and female have three anterior lips with small, tooth-like

projections.

Morphology

• Fertile eggs: 45-75 um by 35-50 um

• Thick hyaline wall around a one cell-stage embryo

• Brown, bile colored outer layer

• Decorticated: no mammillated outer coat

•Unfertile Eggs: up to 90 um•Elongated with mass of highly refractile granules.

Life Cycle

Life Cycle

Definitive host:Humans

Adult worms:Live in lumen of

the small intestine

Female can

produce 200,000 eggs/dayPassed in the feces

Life Cycle

Eggs: in the environmentUnfertilized: not infective

Fertilized: embryonateInfective after about 18 days depending on the environment

Optimum: Moist, warm, shaded soil

Life Cycle

Human ingests infected egg (Fecal-Oral Route)

Larvae hatch inside the human host

Invade intestinal mucosa:Carried through systemic circulation to the lungs

Larvae mature here (10-14 days)

Penetrate aleveolar walls into the throat

Swallowed!

Small intestine: Adults

Dum Dum Dum…

http://www.indyarocks.com/videos/Why-is-eating-dirt-is-bad-Ascaris-lumbricoides-2296565

For Your Information…

It takes 2-3 months from ingestion of the fertilized (infectious) egg to mature into the adult female.

Adult worms can live 1-2 years.

Sometimes, it is found concurrently

with whipworm.Both are soil-transmitted

helminth infections?

Pathogenesis

Ascaris lumbricoides causes ascariasis:Adults: abdominal discomfort, loss of appetite, and pain• Intestinal obstruction• Affects growth of children• Exit: mouth, tear duct, nose• Fever? Invades other organs

• Liver abscess• Peritonitis• Secondary infection in the lungs

Larva: Loffler syndromeAsthma, edema, pneumonitis, and

eosinophilic infiltration

Diagnosis

Diagnosis: The egg in a stool sample

X-ray: bolus of worms

Complete Blood Count:

EosinophiliaHistmines

Peroxidase

Treatment

Mebendazole (Vermox): chewable tablet taken twice a day; minor side effects

Blocks of uptake of glucose and other nutrients

Pyrantel pamoate: combination of pyrantel and pamoic acid; sometimes paired with praziquantel

Paralysis of helminths

Albendazole: has not be approved; boradspectrum

Depletes their glycogen stores

No energy=death

Prevention

We are making this a discussion, so put on those thinking hats!

Prevention

Proper hygiene and sanitation: wash your hands!!!!

Wash produce properly before consuming

Bleach doesn’t work, iodine does!

Dispose feces away for habitationsThis prevents contaminated food and water sources

Use a toilet

Eggs can live in the soil for 1-3 years

Epidemiology

1.5 billion infections in the worldPrimarily in Africa and Asia

About 4 million of these are in the United States.