A case of human pulmonary dirofilariosis attributed to D.repens in Italy

Dirofilaria repens, which occurs only in the Old World, is one the species more frequently involved in human dirofilariosis. The worm is usually detected in superficial locations (subcutaneous or submucosal tissue, derma, exceptionally muscles), and rarely in internal ones (lung, gastro-splenic ligament, omentum, peritoneal cavity, mesocolon, pancreas, perirectal region) (Gabrielli et al., 2008, Parassitologia, 50: 47). Pulmonary lesions detected and non mis-diagnosed as a lung tumour, have been mostly attributed to D. immitis, and only few to D.repens. Aim of this communication is to report a human case of pulmonary infection due to D.repens in Italy, where the parasite has been rarely observed in this location. In 2010 a 17 year-old man was admitted to the Cotugno Hospital (Naples, Italy) with a diagnosis of pneumothorax. During the surgical intervention, a solitary nodule was evidenced, therefore an incisional biopsy was performed to assess the origin of the lesion in haematoxylin-eosin stained sections. Microscopic analysis evidenced transversal and longitudinal sections of a worm whose morphological features (parasite diameter, cuticle thickness, cuticular ridges, number and distribution of the fibres in the muscular layer, lateral cordae) can be ascribed to a female specimen belonging to genus Dirofilaria, subgenus Nochtiella, very probably D. repens. Unfortunately, molecular analysis of the worm in order to support morphological identification was not possible, as the entire nodule was been submitted to the histological analysis. As suggested by Pampiglione and co-workers in 2009, most pulmonary cases of dirofilariosis have been attributed to D.immitis by analogy with human infections from America and with the location usually reached in the dogs. The present observation provides further evidence that also D. repens can reach the lung in humans, as previously demonstrated and assessed by means of morphological and biomolecular tecniques (Pampliglione et al., 2008, Annals of Tropical Medicine & Parasitology, 102 (6): 499–507). Such pulmonary infections are important because they are frequently mistaken for primary or metastatic lung tumours, leading to major surgery that is often, if not always, unnecessary (Ro et al., 1989, Human Pathology, 20: 69–76).