Dirofilaria immitis (heartworm) is a zoonotic and an emerging disease, expanding in Europe. In Bulgaria, the presence of the parasite has been described in many regions. However, canine heartworm has hardly been evaluated in the capital of the country and, therefore, the aim of this study was to evaluate the prevalence and distribution of canine heartworm in Sofia. Eighty stray dogs from the city of Sofia and the metropolitan area were analysed for circulating D. immitis antigens. The prevalence was 31.25 %, being 34.7 % in the metropolitan area and 25.8 % in the city of Sofia. The current results are among the highest reported in the country. This could be due to the lack of prophylactic measures against infection in these dogs, but also to the spread of D. immitis into non-endemic countries. Stray dogs may act as an important reservoir of heartworm being a risk for client-owned animals and for the development of pulmonary dirofilariosis in inhabitants. The results show the need to establish further epidemiological studies and prophylactic campaigns for stray and client-owned animals, as well as to create awareness campaigns about the severity and importance of this disease for both animals and humans.
