Woman Had White Maggots Covered in Black Dots Living in Arm for Months

A woman who had recently traveled through Central and South America discovered a botfly larva wriggling out of a sore on her arm five weeks later.

According to the case study, published in the British Medical Journal, the anonymous woman had two lesions on the left wrist, which she said developed after she had been bitten by a mosquito.

"In the first week I felt extreme itchiness and shooting pains down the length of my forearm. Over the first two weeks, the bumps grew and remained red/inflamed. The itchiness started to subside, but the pain continued.

"Pus and a clear, yellowish liquid would leak out of the two bumps, and the bumps were hard to the touch. I never saw anything move, nor was I suspicious of anything growing under my skin," the patient wrote in a Patient's Perspective section of the BMJ paper.

botfly larvae
Stock image of human botfly larvae. A woman who was traveling across South and Central America found two larvae inside a boil on her arm five weeks after returning home. iStock / Getty Images Plus

"About a month and a half after the initial appearance of the bumps, a scab formed over the larger, lower bump. The scab stayed for maybe two days until I had mindlessly picked it off; when this happened, I saw a small, but deep, hole.

"I squeezed the bump (I had tried previously to squeeze the bump but nothing except liquid had emerged) and a thick, white sac-like shape emerged covered with black dots. I squeezed some more, and the tail of the larva emerged, and the whole thing eventually popped out. With very little convincing required, I headed to hospital," she said.

It was determined that the larva was that of a botfly. Botflies, also known as warble flies, heel flies, and gadflies, are parasitic flies native to the Americas. Dermatobia hominis, the human botfly, is the only botfly species that parasitizes humans, and can be found across South and Central America.

"The lifecycle of the human botfly is fascinating," Robert A. Schwartz, a professor of dermatology at Rutgers New Jersey Medical School, told Newsweek.

"The female botfly embeds several of its eggs on a blood-sucking arthropod such as a mosquito, fly, or tick, using a paste-like chemical the botfly manufactures. When the given arthropod lands on a human, the warmth triggers the botfly egg hatching. The arthropod feeds on the human, leaving a bite. Then the botfly larva crawls into the bite, embedding itself inside the host's flesh using its hooked mouth to form a breathing hole," he said.

According to Schwartz, the botfly larva then develops inside the host and feeds off protein and debris from dead blood cells and the body's inflammatory reaction to the invader.

"The maggot remains in the upper layer of skin for up to 10 weeks before "escaping" to pupate in the local environment and completing its life cycle. The live fly doesn't emerge from the infected person's skin," Cameron Webb, an associate professor in medical entomology at the Sydney Institute for Infectious Diseases, University of Sydney, told Newsweek.

According to the patient in the paper, after she arrived at the hospital an ultrasound scan was performed that revealed a second larva in her wrist, leading her to have it extracted that same afternoon.

"Since the removal of the larva, about a month ago, I have had no itchiness or pain and the bumps are no longer raised/inflamed. The spots remain slightly red, but nothing compared with what they were beforehand," she said.

Botflies can be embedded in less easily reached locations than this patient's arm, with other gruesome case studies involving the maggot growing inside somebody's eyelid, and another inside the glans of a penis.

One method of extracting the maggot in cases where it is inaccessible by tweezer or syringe includes the use of ivermectin, an antiparasitic medicine, which causes the larva to exit the body.

Humans aren't the only species that suffer from these parasitic larvae.

"In North America there are several botfly species that infest deer and rodents and other species," Jory Brinkerhoff, a parasitism professor at the University of Richmond, told Newsweek.

"Despite the name, the human botfly will parasitize non-human species as well. More locally, I occasionally encounter deer that have nasal botfly larvae and mice and squirrels are frequently parasitized by botfly species that do not affect humans," he said.

According to the BMJ paper, travelers should use of protective clothing and insect repellent to avoid infection by the parasite.