Infectious Disease Compendium

Ascaris

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