An army of worm larvae hatch from the man’s buttocks, visibly creeping under his skin

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Enlarge / A filariform strongyloides larva.

Doctors in Spain have diagnosed a man with an unusual roundworm infection after seeing an army of larvae writhing and crawling under his skin, covering his entire body in an ever-changing rash.

Doctors reported the man’s rare hyperinfection this week in the New England Journal of Medicine, highlighting the unusual sight of a wriggling, slippery rash that follows the movements of individual parasitic prowlers. The official diagnosis was hopper currents of Strongyloides.

The unfortunate patient seemed to have a perfect storm of risk factors for developing the rare and nasty infection. The 64-year-old worked in sewage management and had previously been diagnosed with metastatic lung cancer. For the previous three years, doctors had noted episodes of eosinophilia – unusually high levels of disease-fighting white blood cells – which may be an indicator of a parasitic infection.

At the time of the larval incursion, the man was in hospital because a cancerous growth had begun to press on his spinal cord. Doctors had treated him for several days with a high dose of glucocorticoid, which suppresses certain immune responses and creates the perfect conditions for parasitic worms to thrive.

Vermin Invasion

A wavy rash moving on the man's body.  Panels B and C show larval movement over 24 hours.
Enlarge / A wavy rash moving on the man’s body. Panels B and C show larval movement over 24 hours.

The worm in this case is Strongyloides stercoralis, a nematode or roundworm known to infect humans. Infections begin when a person is exposed to contaminated soil or sewage. Worms can mature and reproduce there, and legions of small larvae – around 600 micrograms in length – can emerge, burrow directly into a person’s skin unnoticed and work their way into the intestines by various routes. In some cases, the larvae make their way to the lungs, are coughed up, and then swallowed to reach their final destination. Once in the intestines, the worms embed themselves in the lining of the small intestine and reproduce. The larvae that hatch there are then excreted in the faeces to start the process over again or penetrate the skin in the perianal region, resulting in “auto-infection”.

This last cycle, the most disturbing, seems to have occurred in the cancer patient. Doctors noted that the problems started with an itchy rash and mild diarrhea. The red, wavy skin lesions originated in his perianal area and then began to migrate under his skin, reaching his entire trunk and limbs. Doctors drew individual red squiggles on her skin with a pen and noted that 24 hours later the squiggles had moved.

The changing rash and the identification of Strongyloides stercoralis larvae during a stool examination – confirmed the diagnosis. Doctors prescribed the man the anti-parasitic ivermectin, and the rash and diarrhea improved.