First Case of Human Anisakiosis in Greece: Acute Invasive Infection Mimicking Peritoneal Malignancy

Abstract

Consumption of raw and mildly processed seafood, in the context of modern Western world eating trends, is recognized as a major driver for human fish-borne infections. However, these zoonoses and their unfamiliar risks remain neglected and underappreciated among European diagnosticians. In contemporary Europe anisakidosis is one of the most important fish-borne zoonoses. It is caused by ingesting the third-stage infective larvae of the nematode parasites that belong to the family Anisakidae. The case described herein, is an intestinal and ectopic form of anisakiosis (Anisakis spp.), causing symptoms of subacute abdomen and masquerading as an intraperitoneal malignancy. It is the first anisakidosis case reported in Greece, affecting a young patient who had been repeatedly exposed to the parasite by consuming homemade raw fish. Right hemicolectomy, omentectomy and excision of a descending colon nodule were uneventfully performed. The pathology report confirmed granulomatous tissue with eosinophilic infiltration and parasites that were morphologically and molecularly identified as Anisakis spp. Although challenging, acquiring an accurate diagnosis of anisakidosis can prevent unnecessary surgery, as the infection typically is self-resolving, and if treatment is deemed necessary, it can be limited to antiparasitic medication. However, in rare cases, extra-gastrointestinal migration of larvae can cause severe damage with practically unknown risks, posing a diagnostic and therapeutic dilemma. In such a clinical case scenario, surgical exploration can decisively contribute to a definitive diagnosis and early identification of intraabdominal complications necessitating surgical intervention.

Keywords: Anisakis; anisakiasis; anisakidosis; colectomy; ectopic; extra-gastrointestinal; foodborne; intestinal anisakiasis; sushi; zoonotic.

Figure 1

Abdomen contrast-enhanced MRI of a patient with invasive intestinal anisakiosis. (A): Distal ileum lesion (black arrow). (B): Multiple lymph nodes along ileocolic vessels (white arrows).

Figure 2

Colectomy of a patient with invasive intestinal anisakiosis. Multiple enlarged lymph nodes (arrows) and a lesion in the distal ileum (circle, also shown in Figure 1A) are visible.

Figure 3

Two histological sections (hematoxylin and eosin; original magnification ×400) of Anisakis spp. in surgically excised granulomatous lesions of the intestine and the mesentery. The cross-section of the nematode’s body shows a smooth cuticle (C), a pseudocelomatic cavity (P), polymyarian/coelomyarian type muscle layer (M), the intestinal tract (I), prominent Y-shaped (clover-shaped) lateral chords (arrows), and the excretory organ (asterisk). The parasite is surrounded by granulomatous tissue with inflammatory cells, mainly eosinophils (EO).