A scariasis

Ascariasis is an infection of the small intestine caused by the roundworm Ascaris lumbricoides.

As larval stages travel through the body, they may cause visceral damage, peritonitis and inflammation, enlargement of the liver or spleen, toxicity, and pneumonia. A heavy worm infestation may cause nutritional deficiency; other complications, sometimes fatal, include obstruction of the bowel by a bolus of worms (observed particularly in children), obstruction of bile or pancreatic duct.

Children are infected more often than adults, the most common age group being 3-8 years. The infection is likely to be more serious if the nutrition is poor. Eating uncooked food grown in contaminated soil or irrigated with inadequately treated wastewater is a frequent avenue of infection.

Roughly 1.5 billion individuals are infected with this worm. The disease is found worldwide, with greatest frequency in tropical and subtropical regions, and in any areas with inadequate sanitation.

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Sources:
http://en.wikipedia.org/wiki/Ascariasis
http://www.who.int/water_sanitation_health/diseases/ascariasis/en/
Picture:
http://images.google.com/images?hl=en&lr=&rls=GGLD%2CGGLD%3A2005-12%2CGGLD%3Aen&q=ascariasis