Pseudo-tumor of the lung, a rare clinical presentation of dirofilariasis

Intramuscular dirofilariasis mimicking an orbital metastasis in a patient with breast cancer

We present the unusual case of a 74 year-old female with a history of breast cancer who presented with acute painless orbital swelling and vertical diplopia. MRI revealed a focal enhancing mass within the superior rectus muscle. As the concern for metastatic disease was high, surgical biopsy was performed and revealed an unusual mimicker of metastatic disease, the parasitic infection dirofilariasis.

Human and animal dirofilariasis: the emergence of a zoonotic mosaic

Dirofilariasis represents a zoonotic mosaic, which includes two main filarial species (Dirofilaria immitis and D. repens) that have adapted to canine, feline, and human hosts with distinct biological and clinical implications. At the same time, both D. immitis and D. repens are themselves hosts to symbiotic bacteria of the genus Wolbachia, the study of which has resulted in a profound shift in the understanding of filarial biology, the mechanisms of the pathologies that they produce in their hosts, and issues related to dirofilariasis treatment. Moreover, because dirofilariasis is a vector-borne transmitted disease, their distribution and infection rates have undergone significant modifications influenced by global climate change. Despite advances in our knowledge of D. immitis and D. repens and the pathologies that they inflict on different hosts, there are still many unknown aspects of dirofilariasis. This review is focused on human and animal dirofilariasis, including the basic morphology, biology, protein composition, and metabolism of Dirofilaria species; the climate and human behavioral factors that influence distribution dynamics; the disease pathology; the host-parasite relationship; the mechanisms involved in parasite survival; the immune response and pathogenesis; and the clinical management of human and animal infections.

Human Dirofilaria repens infection in Serbia

Human infection by Dirofilaria repens in Serbia has been increasing steadily. The first case was reported in 1971, presented in the form of a single subcutaneous nodule on the back of a young boy. As established by a literature search, eight additional cases were reported until mid-2001. The most frequent site of infection was subcutaneous tissue, with the exception of two cases, in which parasites were found in subconjunctiva and epididymis. Our study, conducted from 2001 to 2008, encompasses 19 new cases. Most of them (63.1%) presented as ocular or periocular infections, in which the parasite was typically found under the conjunctiva. In other cases a parasitic nodule was localized in the temporal region of the head, epididymis, testicle, abdomen, breast or arm. The diagnosis was made by morphological and histological analysis of the extracted intact worms and parasite sections from the tissue. Morphology of the filarial worms was well preserved in more than half of the cases (12/19) and there was never more than one parasite found inside the lesions. Adult worms and immature nematodes were observed in nine and seven cases, respectively. Furthermore, in two cases microfilariae were discovered inside the pseudocoelom, sections of the female reproductive tubes filled with clearly visible larval stages. Dirofilaria repens infection was diagnosed by its morphological features (17/19) or by performing polymerase chain reactions (PCR) using paraffin-embedded tissues (2/19) in the cases where the morphology was insufficient for identification and the parasites had been determined initially as Dirofilaria spp. The amplified 246 bp PCR product showed that the worms were D. repens.

Detection of Dirofilaria (Nochtiella) repens DNA by polymerase chain reaction in embedded paraffin tissues from two human pulmonary locations

We here report two new cases of human pulmonary dirofilariasis in men aged 62 and 64 from Northern and Central Italy, respectively. Both were asymptomatic and the infections were discovered incidentally when chest radiographs taken for another reason revealed the presence of a coin lesion. The initial clinical diagnosis was oriented towards a lung tumour, and an excisional lung biopsy after thoracotomy was necessary for the final diagnosis. Pathologically, the lesion consisted of a roundish subpleural infarct with a central thrombotic artery containing sections of an immature nematode: Dirofilaria repens was diagnosed histologically in one case, the necrotic condition of the worm allowing only genus identification, Dirofilaria, in the other case. In both samples, PCR analysis amplified a 246 bp product, specific for the IpS insert 11 of D. repens. The authors stress the role of PCR in the diagnosis of this parasite from paraffin samples, also in cases in which identification of the species was not possible by conventional morphology due to poor conservation of the worm. These cases represent the first PCR-based diagnosis of D. repens in a human pulmonary dirofilariasis on samples embedded in paraffin.