Microbiology
A roundworm. 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.
Early infection may result in unusual development and morphology of nematode and trematode eggs making diagnosis difficult (PubMed).
Epidemiologic Risks
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).
Symptoms
Mostly asymptomatic, can cause bloating and malnutrition 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 be seen on barium contrast studies or on CT. Ew.
Look for O&P in stool or lung as symptoms suggest.
Treatment
Albendazole 400 mg po once.
Mebendazole 100 mg po bid for 3 days or 500 mg po once.
Ivermectin 150-200 mcg/kg po once.
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.
Notes
And it was a problem, along with whipworm, for Crusaders (PubMed) and Richard III (Pubmed). Nothing like spending your time in Medieval latrines.
The oldest eggs discovered are 24,000 years old.
Last update: 01/06/19