Molecular and morphological characterization of Oxyspirura conjunctivalis (Spirurida: Thelaziidae) in a captive gibbon with evidence of cockroach intermediate hosts.

Eyeworms of the genus Oxyspirura infect a wide range of avian hosts worldwide, with more than 50 species described. However, Oxyspirura conjunctivalis (syn. O. youngi) and the recently described O. tamarina have been reported exclusively from captive primates in zoological gardens in Europe and North America. In this study, we report the first record of Oxyspirura infection in a captive Bornean white-bearded gibbon (Hylobates albibarbis) in Japan. Five adult worms recovered from the conjunctival sac measured 7.8-11.1 mm in length and 0.29-0.35 mm in width and exhibited a bipartite buccal capsule, pointed posterior ends in both sexes, markedly unequal spicules with a gubernaculum in male worms, and a vulval opening near the anus in oviparous female worms, indicating their classification in the genus Oxyspirura. Morphological features and the available ribosomal RNA gene (rDNA) sequence of the present specimens were identical to those of O. conjunctivalis previously collected from captive primates at the Moscow Zoo and O. tamarina from captive primates in the Czech Republic. Parasitological examination of smokybrown cockroaches (Periplaneta fuliginosa) collected from the gibbon enclosure revealed encysted larvae in their fat bodies. The mitochondrial cytochrome c oxidase subunit I (cox1) sequence of these larvae was identical to that of the newly collected adult worm, indicating the establishment of a transmission cycle for O. conjunctivalis within the zoo. Furthermore, the small- and large-subunit rDNA and cox1 sequences, together with morphological features, demonstrated that O. conjunctivalis and O. tamarina were almost identical, indicating their conspecific relationship.