Hooked: How parasites worm their way into you

There are lots of hooks in life. We all know The Hook, the one local newspaper that includes this column. Peter Pan just loved Captain Hook. I guess Mark Wahlberg threw a few good left hooks in The Fighter. Amish people dress using hooks and eyes. Natalie Portman hooks up in her new movie, No Strings Attached. Dr. Hong’s jokes are always hook, line, and stinker.

What about hookworm?

Hookworm is a parasite. There are two types depending on geography: Necator americanus and Ancylostoma duodenale. Necator americanus is on our turf (literally): North and South America, central Africa, Indonesia, islands of the South Pacific, and parts of India. Ancylostoma duodenale is in Mediterranean countries, Iran, India, Pakistan, and the Far East.

These parasites need warm moist soil, so they tend to survive in warm regions with more than 40 inches of rainfall per year. It’s estimated that 740 million people around the world are infected with hookworm. Holy United Nations, Batman.

There are many reasons not to walk barefoot outside, and hookworm is one. Infection occurs via the skin, most often through the foot. If there is human feces in the soil that carries the hookworm, infection can occur. (Ancylostoma duodenale can be taken in by mouth as well, though.)

Yes, if sanitation isn’t good, human manure and all the infections that come with it can make a beeline to your body. So even wearing open footwear can expose the feet to parasites. (Heidi Klum will not be happy about this.)

In the life cycle of hookworms, the eggs hatch in soil, and the larvae mature to become infective. It only takes about three mature larvae to raid the human body and cause a full infection. These toddler hookworms wiggle their way through the skin, and small itchy red bumps usually form. Sometimes, a serpentine track that Thomas Jefferson would be proud of can be seen in the skin.

These larvae travel through the blood and take refuge in the lungs. As they mature into teenagers, which is about 8-21 days after entering the skin, they go into the airways to be coughed up and swallowed into the gut. Studies of people who volunteered to be infected with hookworm revealed that most folks don’t really notice the attendant mild cough and throat irritation.

The larvae then attach to the lining of the small intestine to feed and become adult worms and can cause nausea, vomiting, diarrhea, and abdominal pain.

The male hookworms fertilize the female hookworms, who then lay eggs in the gut. (I’m curious. How do the males fertilize the females? Worm sex? It seems like a gut-wrenching experience.) The human poops out the fertilized eggs to infect some other unsuspecting victim. It takes at least six to eight weeks for eggs to be detectable in a human stool after initial infection. And the hookworms can live as long as 18 years!

Because hookworms steal blood, iron, and protein in the gut, malnutrition and anemia can occur in the human host. So fatigue, weight loss and pale skin can be tell-tale signs.

Because stool samples can take so long show evidence of hookworm, one can’t really diagnose it in people who suspect they have it. A blood test can show evidence of parasitic inflammation, but that isn’t a huge help. Treatment is done with anti-parasitic medicine such as mebendazole.

The moral of the story is don’t play tackle football in subtropical or tropical regions. Don’t go walking Barefoot in the Park like Robert Redford. Don’t get hooked to parasites. 

Dr. Hook cracks a joke or two, but he's a renowned physician with an interesting website,www.drjohnhong.com. Email him with your questions.