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Epidemiology and Pathology

Man acquires ascariasis by ingesting food. water or soil contaminated with embryonated eggs (Fig. 10.1). Children are much more commonly and severely infected than adults because ascariasis is usually a "backyard" infection. In areas where sanitation is poor, parasitized children who defecate in the yard around their home contaminate the soil with Ascaris eggs which, after embryonation, offer a fertile source of' new infection for other children or reinfection for themselves. Infants and young children ingest infective eggs by placing contaminated fingers or toys in their mouths or by eating dirt. Numerous investigators have observed that the highest rate of infection with Ascaris is in children between 1 and 15 years of age, although in hot and humid areas of rural Africa, Asia, and Latin America up to 93% of all inhabitants in some villages may be infected.

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Fig. 10.1 (A and B) Life cycle of Ascaris lumbricoides.

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