Molecular analysis ofDirofilaria repensremoved from a subcutaneous nodule in a Japanese woman after a tour to Europe

Jun Suzuki,Utako Okata,Hitomi Matsuzaki,Ko-Ron Chen,Seiki Kobayashi,Mariko Mori,Satoshi Iwata

doi:10.1051/parasite/2015002

Abstract

A premature female Dirofilaria species, subsequently identified as Dirofilaria repens by its morphological features and mitochondrial 12S ribosomal RNA (12S rRNA) gene sequence, was removed from a subcutaneous nodule of the right temporal region of the head in a Japanese woman 2 years after she noticed swelling of her left calf following an insect sting during a tour to Europe; headache symptoms were noticed a few months later. The sequences of the mitochondrial 12S rRNA and cytochrome c oxidase subunit I genes from the organism were almost identical to those of sequences AM779772 (100% homology, 337/337) and AM749233 (99.8% homology, 536/537) of D. repens isolated from humans in Italy. However, the phylogenetic position of the 18S rRNA-internal transcribed spacer 1-5.8S rRNA region was in the same cluster as that of sequence JX290195 of Dirofilaria sp. “hongkongensis” (96.7% homology, 348/360), which was recently reported from Hong Kong as a novel Dirofilaria species. Information on regional genetic variation in D. repens isolated from animals and humans remains scarce. We report the detailed genetic features of this filaria as a reference isolate from a specific endemic area, to enrich the genetic database of D. repens.

Highlights

Dirofilaria repens Railliet & Henry, 1911 [21] infects dogs, cats, and other carnivores in the Old World
The measured values of the external longitudinal ridges of the Dirofilaria species in the present case were 3–4 lm in height, and they were spaced at 15–17 lm intervals and numbered 118–122. These values are generally consistent with values reported for adult female D. repens removed from three human patients (Table 2), and their morphologies differ from those of D. immitis [19], Dirofilaria tenuis [15], and D. ursi [2, 27, 28]
The endemic area of D. repens is widespread in the Old World (Eurasia and sub-Saharan Africa), and regional genetic diversity of D. repens has been described for the 12S rRNA [6, 20] gene, the COI [6] gene, and the internal transcribed spacer 1 (ITS1) region [13, 25] and reported in GenBank

Summary

Introduction

Dirofilaria repens Railliet & Henry, 1911 [21] infects dogs, cats, and other carnivores in the Old World. In Japan, D. repens is an uncommon parasite (no cases of infection with D. repens in domestic dogs have been reported as of 2014), and in the majority of animal and human dirofilariasis cases, Dirofilaria immitis was identified as the etiological agent. The sources of infection are not clear, two human cases caused by domestic infection of D. repens have been reported in Japan [11, 12]. We report a suspected case of imported dirofilariasis in a Japanese woman, caused by D. repens from Europe. Dirofilariasis caused by D. repens is highly prevalent in the Mediterranean region of Southern Europe (e.g., Spain, the south of France, and Italy) [17]. In Italy, 298 human cases have been reported, and in Bulgaria, there have been an increasing number of people infected by D. repens in recent years [10]. As a novel Dirofilaria species, Dirofilaria sp. ‘‘hongkongensis’’ has been reported from Hong Kong [25], based on the sequence homology of the 18S-internal transcribed spacer 1 (ITS1)-5.8S rRNA region, a reference for the differentiation of filarial species [13]

Methods

Results

Conclusion