Human case of subcutaneous nodule because of a novel genetic variation of Dirofilaria sp.

A 75-year-old man presented with a 1-cm large elastic soft subcutaneous nodule on the left side of the umbilicus, which when excised showed presence of a helminthic form within the granulomatous lesions. Morphologically, the helminth was considered to be of the genus Dirofilaria, and the patient showed increased serum antibody titer against canine filaria. The partial DNA sequence of the mitochondrial 12S rRNA gene locus of this clinical isolate showed the highest nucleotide identity (89.6%) with Dirofilaria repens; however, the phylogenetic analysis addressed the haplotype and Dirofilaria ursi as outgroups of the clusters of D. repens and Dirofilaria immitis, which are the causal agents of most human dirofilariasis. As like bear filaria D. ursi, a wide variety of other carnivore-parasitizing filaria species have rarely been reported in humans. The newly detected genetic haplotype in this case may correspond to one of these species of Dirofilaria, though the genetic references are not available thus far.