Ascariasis pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Imtiaz Ahmed Wani, M.B.B.S

Pathophysiology

Life cycle

Adult worms (1) live in the lumen of the small intestine. A female may produce approximately 200,000 eggs per day, which are passed with the feces (2). Unfertilized eggs may be ingested but are not infective. Fertile eggs embryonate and become infective after 18 days to several weeks (3), depending on the environmental conditions (optimum: moist, warm, shaded soil). After infective eggs are swallowed (4), the larvae hatch (5), invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs . The larvae mature further in the lungs (6) (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed (7). Upon reaching the small intestine, they develop into adult worms (8). Between 2 and 3 months are required from ingestion of the infective eggs to oviposition by the adult female. Adult worms can live 1 to 2 years.

Genus and Species	Ascaris lumbricoides
Common Name	Giant Intestinal Roundworm
Etiologic Agent of:	Ascariasis
Infective stage	Embryonated Egg
Definitive Host	Man
Portal of Entry	Mouth
Mode of Transmission	Ingestion of Embryonated egg through contaminated food or water
Habitat	Small Intestine
Pathogenic Stage	Adult Larva
Mode of Attachment	Retention in the mucosal folds using pressure
Mode of Nutrition	Feeding of Chyme
Pathogenesis	Larva – pneumonitis, Loeffler’s syndrome; Adult – Obstruction, Liver abscess, Appendicitis. With Blood-Lung Phase along with Hookworms and Strongyloides stercoralis.
Laboratory diagnosis	Concentration methods and Direct Fecal Smear: Kato-Katz
Treatment	Albendazole, Mebendazole, or Pyrantel Pamoate
Diagnostic Feature - Adult	Female - prominent genital girdle
Diagnostic Feature - Egg	Coarse mammilated albuminous coating

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