A round worm. Ascaris lumbricoides (humans) and A. suum (pigs). Probably the same species in different hosts (PubMed). Pigs and humans are a lot alike. My wife would say men and pigs are identical.
They can be quite large: 15-30 cm long and 3-6 mm thick.
Fecal-oral. Humans crap in the soil, you eat the soil, the worm goes along for the ride. Myocardial infarction be damned, that's why I only eat deep fried food. In Cornwall (England) A. suum has been spread from pigs (its normal host) to cause human disease.
The female makes 200,000 eggs per day for a year. The eggs are infectious after two weeks in soil and can persist in soil for 10 years.
At least 1 billion people are infected worldwide. That's a shi....never mind.
Pig farmers also spread the disease in the US, with cross-transmission between humans and pigs (PubMed).
The oldest eggs found are 24,000 years old.
Mostly asymptomatic, can cause bloating and malnurition in the GI tract.
Löffler's syndrome: cough, transient pulmonary infiltrates and eosinophilia.
Occasionally they will be found clogging up the biliary system (I was called by a surprised surgeon once), pancreatic duct or causing small bowel obstruction if a huge worm load.
Everyone once and a while someone will pass a worm and freak, although more often than not I see a garden worm that somehow went from garden to pants to toilet.
Sometimes they can seen seen on barium contrast studies or on CT. Ew.
Look for O&P in stool or lung as symptoms suggest.
Mebendazole 100 mg bid x 3 days. Pyrantel pamoate 11 mg/kg orally (maximum of 1 g) is an alternative. In intestinal or biliary obstruction, piperazine, 150 mg/kg initially, followed by six doses of 65 mg/kg q 12-h to paralyze the worm and they pass on through. Ick.