Ascaris lumbricoides Beth Wozney. The largest nematode to infect the human intestine..
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Transcript of Ascaris lumbricoides Beth 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
• 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
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
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