Molecular and pathological characterization of a Dirofilaria sp. infection in a little egret (Egretta garzetta)

Dirofilaria spp. are mosquito-borne filarial nematodes that primarily infect mammals. Here, we describe a filarial nematode infection in a female little egret (Egretta garzetta) from Jeju, Korea. Necropsy revealed multiple slender nematodes (4-6 cm) in the subcutaneous tissues of both legs. Histopathological examination demonstrated granulomatous inflammation with intralesional parasites. Morphologically, the nematodes exhibited a thick multilayered cuticle with prominent longitudinal ridges, consistent with members of the genus Dirofilaria. Molecular analysis based on 18S rRNA and mitochondrial c oxidase subunit I (cox1) gene sequences indicated that the parasite was most closely related to D. repens; however, the level of sequence divergence precluded definitive species-level identification. Phylogenetic analysis further demonstrated that the isolates clustered within the Dirofilaria clade and were clearly separated from avian-associated filarioid nematodes. This study provides molecular and histopathological evidence of a Dirofilaria sp. infection in an avian host and supports incidental infection under natural exposure conditions.