infectious diseases
Ascariasis
Introduction
Ascariasis is infection withAscaris lumbricoidesor occasionallyAscaris suum(a closely related parasite of pigs). Light infections may be asymptomatic. Early symptoms are pulmonary (cough, wheezing); later symptoms are gastrointestinal, with cramps or abdominal pain due to obstruction of gastrointestinal lumina (intestines or biliary or pancreatic ducts) by adult worms. Chronically infected children may develop undernutrition. Diagnosis is by identifying eggs or adult worms in stool, adult worms that migrate from the nose or mouth, or rarely larvae in sputum during the pulmonary migration phase. Treatment is withalbendazole,mebendazole, orivermectin. (See also Approach to Parasitic Infections .) Ascariasis, the most common intestinal helminth infection in the world, occurs worldwide but is concentrated in tropical and subtropical areas with poor sanitation. Prevalence is highest in children aged 2 to 10 years and decreases in older age groups. Current estimates suggest that about 500 million people are infected worldwide, and ascariasis contributes to malnutrition in areas with poor sanitation. It is estimated that ascariasis is responsible for 2,000 to 10,000 deaths worldwide annually, most of which are due to bowel or biliary tract obstruction in children. In the United States, most cases occur in refugees, immigrants, or travelers to endemic tropical areas. Humans are infected withA. lumbricoideswhen they ingest its eggs, often in food contaminated by human feces. Infection can also occur when hands or fingers with contaminated dirt on them are put in the mouth. Humans can also be infected with ascaris (A. suum) from pigs when they ingest eggs from handling pigs or from consuming undercooked vegetables or fruits contaminated with pig feces. WhetherA. suumis a distinct species fromA. lumbricoidesis debated. 