They’re excellent bait for redfish (or red drum), striped bass, flounder, and sheepshead, among other game fish. They are, however, thought to be entirely edible for humans.

Silky Terrier Dog Breed Playing Aro... Silky Terrier Dog Breed Playing Around

Sand flea infections, which are parasitic insects that burrow into people’s skin, are uncommon and haven’t been well reported in the recent 50 years. However, a new paper from Colombia details five cases of “severe” sand flea infestations, demonstrating that this parasite can still cause life-threatening conditions.

According to the findings, which were published today (February 7) in the journal PLOS Neglected Tropical Diseases, the five patients each had hundreds to thousands of sand fleas implanted in their skin and were unable to move as a result of their condition. Due to severe anemia caused by the blood-sucking fleas, one patient required a blood transfusion.

Because the individuals with these infections live in rural places and lack access to health care, such extreme cases frequently go missed by health care providers, according to the paper.

“It’s likely that the true prevalence of this fatal disease is understated.”

Tunga penetrans, or sand fleas, are native to sections of South America, the Caribbean, Sub-Saharan Africa, and Madagascar. Tungiasis is a condition caused by fleas burrowing into the skin of humans, commonly in the toes, soles, and heels.

According to the World Health Organization, fleas sucking the blood of their hosts can grow by a factor of 2,000 in a matter of weeks. Burrowed fleas can cause acute inflammation, pain, and itching, and in severe cases, many sores on the person’s foot can make walking difficult.

Fleas lay their eggs through a hole in the skin, which then fall to the ground and hatch. The burrowed parasite dies after about three weeks, and the symptoms stop.