A worm. Ascaris lumbricoides and A. suum. Probably the same species in different hosts (PubMed). Pigs and humans are a lot alike.
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.
Pig farmers also spread the disease in the US, with cross-transmission between humans and pig(PubMed).
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.