Medical First: Sheep Botfly Larvae and Pupa Extracted from Woman's Sinus in Greece

A remarkable medical mystery on a Greek island has captivated scientists and researchers long after the patient fully recovered. The case began when a 58-year-old woman sneezed and was horrified to find small worm-like organisms expelled from her nostrils. A thorough examination at an ENT clinic revealed an even more startling sight: ten live larvae and one intact pupa of the sheep botfly (Oestrus ovis) had nested inside her maxillary sinus, the air cavity located in the cheekbone next to the nose.

While human larval infestations (myiasis) occur rarely, the discovery of a fully formed pupa stunned the medical community. Researchers from Athens and Heraklion, who published the case in the journal Emerging Infectious Diseases of the US Centers for Disease Control and Prevention (CDC), clarified that according to current biological understanding, a larva pupating inside the living body of a mammal was previously considered biologically impossible.

The Timeline of the Infestation

The incident began about a month earlier. The woman was working outdoors in hot, dry weather near a field where a herd of sheep was grazing. During her work, she noticed a large swarm of flies buzzing around her face. About a week later, she began experiencing pain in her cheeks and the center of her face, followed by a persistent, severe cough over the subsequent weeks. She suffered no other symptoms, and none of her coworkers in the area experienced anything similar. The turning point came with that sudden sneeze in October, which prompted her to visit the doctor, where the ten larvae and the intact pupa were discovered and extracted from her sinus.

Researchers analyzed two of the larvae and a portion of the pupal casing. The first larva was yellowish, about 15 millimeters long, with rows of spines on its underside. The second was light brown, about 20 millimeters long, with wide dark stripes on its back. Both were identified as third-stage larvae, the most advanced developmental stage before pupation. The pupal casing was black, wrinkled, about 10 millimeters long, and contained internal remains.

To rule out any misidentification, scientists extracted DNA from the pupal casing and analyzed two different genetic segments. The results were definitive: the sequences matched the genetic profile of Oestrus ovis registered in the international GenBank database with 100% accuracy.

Biological Deviation and Human Hosts

In nature, the sheep botfly is adapted to reproduce in sheep and goats using a unique reproductive method: the female fly does not lay eggs but squirts tiny first-stage larvae directly into the animal's nostrils while in flight. The larvae crawl up the respiratory tract into the sinuses, attach to the tissues, feed, grow, and molt. Once they reach the mature third stage, the host animal sneezes, expelling them onto the ground, where they pupate in the dry soil and eventually emerge as adult flies.

Humans are "accidental hosts"—mistaken targets for the fly. Typically, when the fly strikes a human, it sprays larvae into the eye, causing an immediate foreign body sensation, inflammation, redness, and tearing. Penetration into the nose, mouth, or ear is considered extremely rare.

Previously, scientists believed these larvae could not survive or develop in humans beyond the first stage. In recent years, a few cases have been documented where they reached advanced stages—primarily in immunocompromised individuals or those with nasal structural issues. However, complete pupation inside a human body cavity is an unprecedented global medical first. The sinus cavity is saturated with moisture, secretions, body heat, immune activity, and bacteria—a hostile environment that typically kills pupae. Even in sheep, larvae trapped in the sinus die, decompose, or dry out, never managing to pupate inside.

Explaining the Medical Anomaly

The patient had two unique factors that shed light on the mystery: she suffered from a severely deviated nasal septum, and an unusually large volume of larvae had entered her body at once. The researchers' primary explanation is mechanical: the crooked and obstructed structure of her nasal septum trapped the larvae in the sinus cavity, preventing them from being expelled during sneezing or nose-blowing. Consequently, they remained inside long enough to mature to the third stage, and one managed to pupate against all odds.

Additionally, the researchers raised a more concerning hypothesis, though they emphasized it remains unproven: this could be an early sign of evolutionary adaptation, with the parasite attempting to develop the ability to complete its life cycle inside a human host. However, a single case does not constitute scientific proof of an evolutionary shift, and broader monitoring is required.

Despite the unsettling nature of the case, it ended in complete medical success. After the ENT specialist extracted all the larvae and the pupa, the woman was treated with nasal decongestant sprays and recovered fully without any long-term damage. Doctors emphasize that the parasite is not contagious and does not spread between humans. The risk remains confined to individuals spending time outdoors near sheep and goat herds in hot, dry regions, such as the Mediterranean basin. For the scientific world, however, this single pupa has turned an accidental sneeze into one of the most fascinating biological puzzles of recent times.