Canine Leishmaniosis is endemic in Mediterranean areas, with a well-documented northward spread. The mass use of preventive measures against sandfly bites (collar and spot-on formulations) was tested in a small focus recently established in an isolated hilly area of north-eastern Italy (Colli Euganei). In 2006 and 2007, a total of 449 dogs living in the southern part of Colli Euganei were screened against Leishmania infantum using an immunofluorescence antibody test (IFAT), and 31 (6.9%) were seropositive. A risk factor analysis clearly described the focus as limited to a small village named Calaone. In 2010, 63 animals from Calaone were sampled and their owners interviewed to verify the effectiveness of the preventive measures. According to what reported by owners, dogs started to be protected in 2006 (66.7% dogs protected), and protection rate incremented (around 90%) during the subsequent years. The seroprevalence value (4.2%) of the youngest age class (<5 years) was significantly lower than other classes, demonstrating that animals born after 2006 had low probabilities of getting infected. Besides, seroprevalence value referred only to dogs living in Calaone was 32.4% (23/71) in 2006-2007 and 20.6% (13/63) in 2010, showing a decreasing trend. Although still preliminary, the results show high sensitization of dog owners and suggest that the mass use of collars and spot-on acts positively in reducing the circulation of L. infantum.