Woman Found to Have Sheep Bot Fly Larvae and Pupa in Nasal Sinuses | Rare Case Report

A Rare Case of Nasal Myiasis: Woman in Greece Expels Sheep Bot Fly Larvae

A 58-year-old woman in Greece experienced a startling medical event: she sneezed out multiple larvae, later identified as those of the sheep bot fly, Oestrus ovis. The case, documented in the March 2026 issue of Emerging Infectious Diseases, is particularly unusual because a pupa – the insect’s cocooned stage – was also recovered from her maxillary sinus. This marks a first-of-its-kind finding, as pupation within a human host had not been previously observed. The incident highlights the potential, though rare, for human infestation by this parasite typically affecting sheep, deer, and goats.

Understanding Sheep Bot Flies and Myiasis

Oestrus ovis is a cosmopolitan parasite, meaning it’s found worldwide, particularly in hot and dry regions, including those bordering the Mediterranean Sea. The fly lays its eggs, which hatch into larvae, directly into the nostrils of grazing animals. These larvae then migrate to the nasal sinuses, where they develop over several weeks. Eventually, the mature larvae are expelled by sneezing or coughing, burrow into the ground, and pupate before emerging as adult flies. This process, known as myiasis, is generally not life-threatening to the animal host, but can cause irritation and secondary infections. Learn more about the sheep bot fly from Wikipedia.

A Deviated Septum and a High Larval Load: Factors in This Unusual Case

Human infestations are accidental, occurring when flies mistake people for their usual hosts. While cases have been reported globally, the development of larvae to the pupal stage within a human is exceptionally rare. Researchers leading the case study, from the Agricultural University of Athens and the University of Crete, believe a combination of factors contributed to this unusual outcome. The woman had a severely deviated septum – a displacement of the cartilage that divides the nostrils – and was exposed to a large number of larvae.

“We hypothesize that the combination of high larval numbers and septum deviation impeded normal egress from the nasal passages, permitting progression to the [third larval stage] and, in 1 instance, pupation,” the researchers wrote in their report. Essentially, the anatomical obstruction created a bottleneck, allowing some larvae to remain within the sinus cavity long enough to complete their development. The experts also acknowledge the possibility that the flies are adapting to utilize human nasal passages for their entire life cycle, though further research is needed to confirm this.

Diagnosis and Treatment

The woman initially presented with worsening pain around her upper jaw and a persistent cough. The “worms” she expelled upon sneezing prompted a visit to an ear, nose, and throat specialist. Examination revealed 10 larvae in various stages of development, along with one puparium – the hardened outer casing of the pupa. The larvae were identified as Oestrus ovis through both visual inspection and genetic analysis, including PCR and DNA sequencing. The patient underwent surgery to remove the remaining larvae and puparium and made a full recovery with nasal decongestants. Read the full case report from the CDC’s Emerging Infectious Diseases journal.

Why This Case Matters: Implications for Public Health

While human myiasis caused by Oestrus ovis remains uncommon, this case serves as a reminder that it can occur. The researchers emphasize the importance of clinicians being aware of the possibility, particularly in regions where the fly is prevalent. The fact that pupation occurred within the human host is particularly noteworthy, as it challenges existing understanding of the parasite’s life cycle and potential for adaptation. Gizmodo provides a layperson’s overview of the case.

Understanding the Biological Implausibility

The researchers noted that the nasal sinus environment typically doesn’t provide the ideal temperature and humidity needed for pupation. The body’s natural defenses – immune responses and the resident microbiota – usually create a hostile environment for pupal development. The successful pupation in this case is therefore considered “biologically implausible,” suggesting that the unique combination of factors – high larval load and anatomical obstruction – overcame these barriers.

What Comes Next: Surveillance and Clinical Awareness

The researchers recommend increased vigilance among clinicians in areas where Oestrus ovis is present. Prompt diagnosis and removal of larvae can prevent complications such as secondary bacterial infections, which can occur when larvae dry out, liquify, or calcify within the sinuses. Further research is needed to understand the factors that contribute to human infestation and the potential for the parasite to adapt to using humans as hosts. Ongoing surveillance of myiasis cases can support track the distribution of the fly and identify any emerging trends. Public health officials will continue to monitor for similar cases and update guidance as needed.