A woman was horrified to learn that a rash on her knee that appeared after a trip to the Caribbean was actually a parasitic worm tunneling underneath her skin.
Two weeks after returning home from her vacation, the unidentified 45-year-old woman noticed a series of raised, wavy lines had developed on her knee.
When it failed to go away on its own, the woman made an appointment with her doctor, who sent her to an emergency room, according to the Daily Mail. There, doctors diagnosed her with a parasitic infection known as cutaneous larva migrans.
She was treated with an antiparasitic drug and has since recovered.
Speaking to Live Science, Dr. Chaiya Laoteppitaks of the Albert Einstein Medical Center in Philadelphia said the woman's case was a "textbook example" of the infection. He said the red, itchy lines are actually the trails left behind by the worm as it moves beneath the skin.
Laoteppitaks and his colleagues published a case report in the Journal of Emergency Medicine on April 8, in which they state that cutaneous larva migrans is caused by a hookworm infection.
Typically found in warm, moist regions of the world, hookworms infect people when their larvae tunnel underneath the skin. The larva proceeds to travel through the body until it reaches the small intestine, at which point it matures and lays eggs. The eggs are then excreted from the body in the person's feces, and the life cycle begins again.
The woman's case is unusual in that the hookworm species that caused her infection -- one of the two worms known scientifically as Ancylostoma braziliense or Ancylostoma caninum -- usually infect dogs and cats, not humans, reports Live Science.
Because humans are not a "definitive host" for these hookworms, Laoteppitaks explained they are unable to complete their life cycle in a human's body. Because of this, they burrow around until they die.
The itchy rash -- known as a creeping eruption -- is the result of the immune system's efforts to attack the worm, which can travel around 1 inch per day. In certain cases, the infected individual can watch the lines of the rash expanding as the worm moves around.
Not all hookworms are bad. In October, a study published in medical journal Science Translational Medicine concluded that a protein generated by certain species of hookworm alleviates asthma in mice, reports the Chicago Tribune. Researchers are now working to figure out whether the protein can be made into a pill and used to treat conditions like asthma and celiac disease in humans.