Abstract

In Mexico, since June 2025, human cases of myiasis caused by Cochliomyia hominivorax (the screwworm) have been identified, prompting health authorities to issue a surveillance alert for potential infections by this fly. Here we report the identification and interdisciplinary management of a case of nasal myiasis caused by Lucilia sericata. In September 2025, a 40-year-old Hispanic man was admitted to the emergency room due to an altered mental status; after a 17-day hospital stay, nasal larvae were detected. The larvae were submitted for morphological identification by microscopy and molecular identification by polymerase chain reaction, using ITS-2 and 16S loci as nuclear and mitochondrial markers, respectively; the amplicons were purified and sequenced, and a Bayesian phylogenetic analysis was performed. Morphological analysis showed that they were L. sericata larvae at different developmental stages (1st to 3rd instars). Molecular analysis confirmed the morphological result, as phylogenetic inferences showed a clear grouping of the sequences within the L. sericata cluster. While remaining vigilant for possible human cases of myiasis caused by C. hominivorax, here, we confirmed by morphological and molecular analysis the identification of an unexpected case of nasal myiasis caused by L. sericata, demonstrating the importance of care in all aspects of thorough epidemiological surveillance and the interdisciplinary management to address these alerts and any related cases.

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