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Ascaris worms

By Rebecca Hernandez

I won’t go into details, but while I was researching the Ascaris worm, I came across a most disturbing picture of this charming creature. My husband then declared quite loudly “I am never going to a tropical country ever again.”
This statement, combined with the impressive prevalence and frankly, gross-out factor of this parasite made it my favourite of the bunch.

The offending picture can be seen here and it’s Nasty with a capital N - you've been warned.

Usually, Ascaris infections are not serious and very treatable, which is good considering how many people actually have them. About a quarter of the world’s population (predominantly in tropical areas, but they’re found all over) is infected with this type of nematode worm. Most people show no symptoms.

Ascaris eggs are found in raw sewage all over the world and accidental ingestion will lead to infection. After the eggs are swallowed, larvae hatch and burrow through the intestine. The young worms then travel to the lungs, where they are coughed up and subsequently swallowed. They then make their way back down to the intestines where they develop into adults, maturing up to a foot long, mating, and finally laying thousands of eggs per day. It seems an improbably bizarre route to take, but at least the young worms see a bit of the world I suppose.

Ascaris worms sometimes leave this normal track of infection to invade such organs as the bile ducts and the appendix. This is especially dangerous if the worm decides to carry some intestinal bacteria along with it.

If a heavy infection is present, large numbers of these worms can congregate to form bolus intestinal blockages, and even come out your throat and nose. Whew. Congratulations, Ascaris. You even beat the 10 meter long tapeworm to number one.

Interesting fact: Ascaris worms have an aversion to some general anaesthetics. If their host is put under they may exit the body, sometimes through the mouth. I imagine surgeons really look forward to those patients.

Danger of death: Heavy infestations can be fatal. In 1986 more than 796 worms weighing 550g were recovered at autopsy from a two-year-old South African girl. The worms had caused torsion and gangrene of the small intestine, leading the girl’s death.

Back to Top Ten Grim Parasites
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08 Apr 2009
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