Evidence of Dirofilaria immitis in Felids in North-Eastern Italy

Dirofilaria immitis is a mosquito-borne nematode, causing heartworm (HW) disease in wild and domestic canids. HW can also affect felids with different clinical patterns from asymptomatic pictures to sudden death, making the monitoring and diagnosis complicated. Canine HW is endemic in North-eastern Italy; however, very little information has been recorded for felids. This study aims to provide new information on HW in felids in North-eastern Italy. Two hundred and six domestic cats from Veneto, Friuli-Venezia Giulia, Trentino Alto-Adige regions (North-eastern Italy), nine captive felids from zoological parks from Veneto, and nineteen European wildcats from Friuli Venezia Giulia were recruited. Sera/plasma was analysed for the detection of anti-HW antibodies (Ab) and HW antigens (Ag); positive blood samples were molecularly analysed, targeting the HW DNA (5S-rRNA gene). Twelve out of two hundred and six (5.8%) cats presented with Ab, and three out of two hundred and six (1.5%) presented with Ag, mainly those from the Veneto region, already known as a canine HW-endemic area. Among Ab-positive cats, two were from Belluno, a mountain province previously considered free, suggesting the expansion of HW into the northern areas. No cats were positive for both Ab and Ag. Three out of nineteen (15.8%) wildcats were Ag-positive, constituting the first HW report in Italy. No captive felids were positive. Dirofilaria immitis DNA was not amplified in positive samples, suggesting the low sensitivity of PCR on blood. This study provides new data on the occurrence of HW in domestic cats and wildcats in North-eastern Italy.