First confirmation of the chicken eyeworm, Oxyspirura mansoni, as a causative pathogen of human cutaneous larva migrans by morphological and molecular evidence.

Human larva migrans is a zoonotic disease caused by larvae of various nematode species, with all previously confirmed pathogens originating from mammalian reservoirs. In 2020, a case series in Vietnam reported instances of cutaneous larva migrans caused by avian eyeworm larvae of the Oxyspirura genus. This nematode genus, belonging to the Thelaziidae family, includes 84 species that mainly parasitize the eyes of various bird species. They utilize different arthropod intermediate hosts, such as cockroaches, grasshoppers, and crickets, in their life cycle. Although the 18S sequences of the larvae were analyzed, the precise identification of the pathogen at the species level remains inconclusive. This study aims to identify the exact causative agent at the species level by analyzing larvae from a patient and adult eyeworms collected from chickens raised in his family using morphological and molecular methods. Molecular analysis of 18S rDNA, ITS2, and cox1 sequences revealed genetic identity between the larva from the patient and adult eyeworms from chickens, as well as with Oxyspirura mansoni from Thailand and Bangladesh. Additionally, morphological examinations further confirmed the adult chicken eyeworms as Oxyspirura mansoni. These findings confirm that O. mansoni larvae are responsible for human larva migrans, marking the first confirmation of nematode larvae from birds (chickens) as a pathogen causing an emerging neglected tropical disease in humans. Given the widespread distribution of this nematode, further research is crucial to investigate this neglected disease, not only in Vietnam but also in other regions. Understanding appropriate treatments and transmission routes is essential to prevent infections in both chickens and humans.