Cytological diagnostics of subcutaneous dirofilariasis imitating proliferative lesions in dogs

Subcutaneous dirofilariasis is a disease in animals caused by invasions of nematodes, most often of the following species: Dirofilaria repens, D. tenuis, and D. striata transmitted by mosquitoes. Until recently, D. repens was endemic to the Mediterranean countries in Europe, but, in recent years, it has also been increasingly reported in Central and Eastern Europe. Cytological preparations collected by a fine-needle aspiration biopsy from nodular lesions located in the subcutis and skin of dogs were used to diagnose suspected proliferative lesions of a cancerous or inflammatory nature. The microscopic examination of the delivered cytological preparations revealed erythrocytes (very numerous), neutrophils and eosinophils (quite numerous), macrophages (single), and whole and/or damaged fragments of microfilariae of Dirofilaria sp. in various numbers. It should be noted that the described infection of Dirofilaria repens in Poland and other countries of this latitude will be an increasingly common pathology in dogs. Due to the mosquitoes transmitting the microfilariae, it is a zoonosis that is an increasingly frequent and a more serious threat to humans. In the differential diagnosis of various types of skin and subcutis lesions of unknown aetiology, dirofilariasis should be considered.