A combined human case of Dirofilaria ursi infection in dorsal subcutaneous tissue and Anisakis simplex sensu stricto (s.s.) infection in ventral subcutaneous tissue

Abstract

Background Dirofilaria ursi is a filarial nematode that parasitizes the subcutaneous tissues of the American black bear (Ursus americanus) and Japanese black bear (Ursus thiabetanus japonicus). D. ursi that has parasitized black bears has the potential to subsequently infect humans. In addition, extra-gastrointestinal anisakiasis is less common in Japan.Case presentationWe report a case of ventral subcutaneous anisakiasis and dorsal subcutaneous dirofilariasis that was acquired in Fukushima, in the northern part of Japan. The patient was an 83-year-old Japanese female, and subcutaneous parasitic granulomas were present on her left abdomen (near the navel) and left scapula. A pathological examination of the surgically dissected tissue sections from each region demonstrated eosinophilic granulomas containing different species of parasites. To enable the morphological and molecular identification of these parasites, DNA was extracted from paraffin-embedded sections using DEXPAT reagent, and the cytochrome oxidase 2 (COX2), internal transcribed spacer 1 (ITS1), 5.8S and ITS2 regions of the Anisakis larvae, and the 5S rRNA region of the male Dirofilaria were sequenced. The PCR products were examined and compared with DNA databases. Molecular analysis of the COX2 and 5S rRNA sequences of each worm revealed that the nematode found in the ventral region belonged to Anisakis simplex sensu stricto (s.s.) and the male Dirofilaria found in the dorsal region was classified as D. ursi.ConclusionThe present case showed a combined human case of D. ursi and A. simplex s.s. infections in subcutaneous tissues. The results of this study will contribute to the identification of unknown parasites in histological sections.

Advances in Omic Studies Drive Discoveries in the Biology of Anisakid Nematodes

“…Functional annotations of parasitic excretory cells may help to clarify the pathogenesis of anisakiasis, because ES products are crucial for parasite infectivity and host immunomodulation. Several aspects of pathogenic behavior are related to larvae’s ability to penetrate host tissue in the gastrointestinal region and even in other locations [ 52 , 53 ], realizing an erratic migration that may cause both an acute response with an associated allergic reaction [ 54 ], or a secondary reaction associated with granuloma. Among congeneric species, A. simplex s.s. and A. pegreffii are the two main etiological agents of anisakiasis [ 55 , 56 ].…”

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

“…It should also be noticed that a case of subcutaneous nodule by D . ursi , which was identified using a PCR‐sequencing methodology, was recently reported in Japan . The molecular systemics and the related techniques are increasingly important for such species identification of parasites.…”

“…Although the reported cases are quite rare, a wide variety of other animal‐parasitizing filaria species such as D . ursi (bear), Dirofilaria tenuis (raccoon), D . ursi (bear) or Dirofilaria subdermata (porcupine), Dirofilaria spectans (otter) and Dirofilaria striata (feline), also can be causal agents of human dirofilariasis.…”

“…immitis , while only three cases of D . repens and a recent case of Dirofilaria ursi have been reported. In this study, we report a case of subcutaneous nodules caused by a newly identified genetic variation of Dirofilaria sp.…”

Zoonoses and potential zoonoses of bears

“…Humans serve as accidental hosts when bitten by an infected black fly and the L3 larvae can still develop into adults in human tissue. Case reports of humans infected with D. ursi have been documented in the United States, Canada and Japan; all patients presented with subcutaneous granulomas/nodules (Beaver et al, ; Yamada et al, ). The two North American cases concerned a 46‐year‐old female fur trapper in Ontario and a 21‐year‐old woman who had been camping in Vermont, while the case in Japan concerned an 83‐year‐old woman who lived in a city frequented by Asiatic black bears.…”