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Microbiology

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Helminthology

Question
30 out of 100
 

All are true about Ascaris lumbricoides except:



A Largest intestinal nematode in man

B Infecting stage is larva

C Site of location is small intestine

D Portal of entry is alimentary canal

Ans. B Infecting stage is larva

a. A lumbricoides is the largest of the intestinal nematodes affecting humans, measuring 15-35 cm in length in adulthood.

b. Infection begins with the ingestion of embryonated (infective) eggs in feces-contaminated soil or foodstuffs. Once ingested, eggs hatch, usually in the small intestine, releasing small larvae that penetrate the intestinal wall.

c. Larvae migrate to the pulmonary vascular beds and then to the alveoli via the portal veins usually 1-2 weeks after infection, during which time they may cause pulmonary symptoms (eg, cough, wheezing).

d. During the time frame of pulmonary symptoms, eggs are not being shed, and thus diagnosis via stool ovas and parasites is not possible. Eggs are not shed in stool until roughly 40 days after the development of pulmonary symptoms.

e. After migrating up the respiratory tract and being swallowed, they mature, copulate, and lay eggs in the intestines.

f. Adult worms may live in the gut for 6-24 months, where they can cause partial or complete bowel obstruction in large numbers, or they can migrate into the appendix, hepatobiliary system, or pancreatic ducts and rarely other organs such as kidneys or brain.

Helminthology Flashcard List

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