Microsporidia Keratoconjunctivitis Identified as an Emerging Zoonotic Threat from Pet Parrots: Clinical and Metagenomic Next-Generation Sequencing Evidence
Microsporidia are opportunistic, obligate intracellular fungi capable of causing keratoconjunctivitis. Because the clinical manifestations of microsporidia keratoconjunctivitis are indistinguishable from those of other etiologies, and the organism is difficult to culture, its diagnosis is challenging. The transmission routes of microsporidia keratoconjunctivitis remain poorly defined, and zoonotic sources have long been suspected but rarely confirmed. Between September 2024 and October 2025, a total of 15 confirmed cases of microsporidia keratoconjunctivitis were identified at Peking University Third Hospital. The diagnosis was established based on Giemsa-stained corneal scrapings and/or metagenomic next-generation sequencing (mNGS) of conjunctival lavage samples. Among these 15 patients, microsporidia spores were observed in corneal scrapings from nine individuals, while 13 tested positive for Encephalitozoon hellem (E. hellem) by mNGS. Notably, all affected patients reported a history of parrot exposure. Self-reported parrot exposures included direct ocular contact (n = 3) and indirect contact (n = 12). Six patients reported that their parrots had exhibited ocular abnormalities and diarrhea before the onset of the patients symptoms, and two patients stated that their parrots had died prior to their clinical presentation. Ocular and fecal samples from three parrots associated with four patients were collected, and all the parrots tested positive for E. hellem by mNGS. These findings provide both clinical and molecular evidence supporting pet parrots as a zoonotic source of microsporidia keratoconjunctivitis. This emerging zoonotic threat calls for greater clinical awareness and attention to animal exposure history during diagnosis.