People sometimes get frustrated when I won’t say “absolutely, positively that cannot happen.” It’s not that I don’t understand or am afraid to make a decision, it’s biology. I can say something is “exceedingly unlikely to happen,” “not something I’d be concerned about” or
“there’s no evidence that’s a concern.” However, Mother Nature likes to keep us on our toes and strange things can happen.

A paper in this month’s Emerging Infectious Diseases (Jung et al, Rare case of enteric Ancylostoma caninum hookworm infection, South Korea) is an example of that.

Ancylostoma caninum is a hookworm that typically infects dogs. It lives in the dog’s intestinal tract, and dogs poop out the parasite eggs. Those eggs hatch into larvae in the environment, and people can be infected by the larvae by touching a contaminated surface. The parasite larvae actually burrow into the skin and cause an incredibly itchy condition as the larvae migrate through the skin for a short period of time. Since people aren’t the natural host, the larvae typically die at that stage in people.  In contrast, in dogs the larvae continue to migrate through the body, eventually making it to the intestine, where they mature into adult worms, produce more eggs and continue the life cycle.

This case report describes an intestinal infection with A. caninum in a person. This isn’t the first time it’s been reported, but it’s rare. The affected person was a 60-year-old man who underwent a colonoscopy. During the procedure, a worm was found attached to the intestine (images A and B below). It was removed and identified as the dog hookworm (image C shows a close up of the worm’s mouth where you can see the “hooks”). He was treated with a dewormer in case that hookworm left any friends behind, and the man recovered. He had some abdominal pain, but whether the parasite was the cause is hard to say. However, he did have an increase in blood eosinophils, a type of white blood cell that’s associated with allergic and parasitic infections.

What does this change?

Nothing.  It’s just interesting oddball infection for physicians to keep in mind, especially in people who live in or have visited areas where canine hookworms are common (e.g. a lot of tropical regions – fecal contamination on beachs is a common source of exposure to hookworm larvae).

Preventing hookworm infections, human or canine, involves proper fecal handling (e.g. stoop and scoop), good hygiene (e.g. wash your hands) and deworming of dogs. Those precautions are nothing special, but these basic measures are often overlooked.