She underwent surgery to remove the mucus chewers, recovering 10 larvae and one pupa in various stages. A genetic test and DNA sequencing confirmed that they were sheep bot flies, as did visual inspection of two third-stage larvae and the puparium.
Third instar oestrus ovis larvae and puerperium obtained from the nasal sinuses of a 58-year-old female patient from Greece. A) The third instar was yellow, with rows of spines on the ventral surface. B) The posterior peritremes were circular with a central button. C) The broken puparium was black and wrinkled and contained the remains of pupae.
Third instar oestrus ovis larvae and puerperium obtained from the nasal sinuses of a 58-year-old female patient from Greece. A) The third instar was yellow, with rows of spines on the ventral surface. B) The posterior peritremes were circular with a central button. C) The broken puparium was black and wrinkled and contained the remains of pupae.
Credit: Kiulos, Kokkas, Piperaki, Emerging Infectious Diseases 2026
nasal novelty
Not only had experts never found pupae in a human snout before, but they also thought evolution to that level was “biologically impossible”.
“The paranasal sinus environment does not meet the temperature and humidity requirements for pupal formation, and host secretions, immune responses, and resident microbiota create an unfavorable environment for pupal development,” the experts, led by medical entomologist Ilias Keulos of the Agricultural University of Athens, wrote.
Nevertheless, this poor woman continued to have worms in her nose. Kiulos and colleagues hypothesized that two factors promoted the fly’s infection in the woman: a large initial dose of larvae and her severely deviated septum.
“From a purely physiological standpoint, we hypothesize that the combination of high larval numbers and septum deviation disrupted normal exit through the nasal passages, allowing the progression [third larval stage] and, in 1 instance, pupation,” he wrote. In other words, there were so many bugs in his clogged nasal passages that they created a barrier in their way out, allowing some to linger longer than usual. The second, equally disturbing possibility is that the flies are getting used to using the human nose for their entire life cycle.
Experts say that in a way the woman was lucky. In animals, third-stage larvae are unable to pupate if they become trapped in the sinuses. Instead, they either dry out, liquefy, or calcify, which can lead to secondary bacterial infection.
From here, Keulos and colleagues warn that physicians should be aware of the possibility of human cases of sheep bot fly infection, which are widely distributed around the world.
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