In this week’s puzzling New England Journal of Medicine (NEJM) image challenge, they present the case of a 10-year-old girl who visited a primary care clinic after she experienced itchy papules on the soles of her feet and on her toes, along with painful lesions surrounding black dots, for a week and a half. Two weeks beforehand, the family had traveled to rural Brazil where the girl had played in a pigsty without wearing shoes. At the doctor’s office, sand fleas were removed from several of the lesions.

Now, medical experts ask: can you name the likely diagnosis?

(Fair warning, this image may not be safe for work and is definitely not safe for table talk. Scroll with caution.)

In a poll with almost 60,000 respondents, 42 percent correctly diagnosed her symptoms as Tungiasis, an inflammatory skin disease caused by burrowing parasitic animals known collectively as Tunga penetrans, which includes chigger flea, chigoe, jigger, nigua, pique, and yes, sand fleas. The infection occurs when one of these pen-point-sized bugs burrows into the skin face down and butt up, leaving room for a small opening at the skin where a portion of its abdomen can breath, poop, and lay upwards of 100 eggs. Within two weeks, the site can swell up to a diameter of 10 millimeters, with the insect still embedded in the skin. Ultimately, it can take between 4 and 6 weeks for the animal to die. In nearly all cases, it happens when hosts walk around barefoot in infected areas.

In 2013, a researcher willingly let sand fleas live in her foot in order to answer a long list of entomological questions bugging tropical health experts. She found that the parasite most likely has sex when females are already inside the host. (We weren’t joking when we said this wasn’t meal-time appropriate.)

Sometimes one flea is all it takes to breed infection, as was the case with an otherwise healthy 35-year-old man who similarly went to Brazil and came back with a brownish lesion on the side of his right big toe where the adult sand flea can be seen decomposing. A quick squeeze of the toe produced several small flea eggs protruding from the skin. Other reports document dozens of sand fleas that burrowed into one individual, as was the case in a group of case studies conducted by the Centers for Disease Control and Prevention where a 2- and 6-year-old had 90 and 96 lesions on their feet, respectively.

Tungiasis is in the family of neglected tropical diseases (NTD), a group of infectious diseases found particularly in tropical climates concentrated in extreme poverty, and affects more than 1 billion people in the world’s poorest regions. As such, the World Health Organization has made it a priority to address these diseases in future objectives.