Ascaris lumbricoides , the largest intestinal nematode known to infect humans, infects 800 to 1200 million people worldwide.
Infection is concentrated in developing countries of Asia, Africa, and Latin America.
Acquired by ingesting eggs that are passed in human feces and mature in the soil. Diagnosis can be made in most cases by finding characteristic eggs in a stool sample.
Infection is usually asymptomatic, but the parasite can produce allergic pneumonitis and intestinal obstruction.
Secondary complications include biliary and pancreatic obstruction, cholangitis, appendicitis, malnutrition, and cognitive and growth delay in young children.
Treated with oral anthelmintic agents.
Ascaris lumbricoides , a fleshy, cylindrical roundworm, is the largest nematode to parasitize the human gut. Adult male and female worms live for about a year, during which time a single female can produce up to 200,000 eggs per day.   An estimated 800 to 1200 million humans are infected worldwide, most of whom are children in developing countries.    Although frequently asymptomatic, ascariasis can cause gastrointestinal and hepatobiliary obstruction, and can contribute to cognitive and growth delay in children.  
Professor of Pediatrics, Microbial Pathogenesis, and Public Health
Yale World Fellows Program
MC declares that he has no competing interests.
Dr Michael Cappello would like to gratefully acknowledge Dr Samantha H. Johnston and Dr Claire Panosian, previous contributors to this monograph. SHJ owns a share in a company (Merck & Co., Inc.) that produces ivermectin, an alternative therapy for ascariasis. CP declares that she has no competing interests.
Stanford Health Promotion Network
Stanford School of Medicine
YM declares that he has no competing interests.
Department of Medical Parasitology and Mycology
School of Public Health
Tehran University of Medical Sciences
MBR declares that he has no competing interests.
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