Exploring Emerging Challenges: Survey on Phlebotomine Sand Flies and Leishmania infantum at the Northern Endemic Border in Europe

Although Switzerland is currently not endemic for canine leishmaniosis (CanL), imported cases of this emerging zoonosis are regularly detected. Also, phlebotomine sand flies, vectors of the causative agent <i>Leishmania infantum</i>, are present in the southern part of the country, in Canton Ticino, and endemic foci of CanL have been recently described in neighboring Italian municipalities. In 2022 and 2023, we evaluated the distribution of phlebotomine sand flies and the presence of antibodies against <i>L. infantum</i> in domestic dogs and cats in Ticino and Mesolcina (Canton of Grisons). An entomological survey was also carried out in the northwest of Switzerland (cantons Basel-Stadt and Basel-Landschaft) close to an area in Germany where potential vectors are present. No sand flies were caught there. In Ticino, 15 out of 20 sites surveyed (75%) were positive for phlebotomine sand flies. <i>Phlebotomus perniciosus</i>, a potential vector of <i>L. infantum</i>, was the most abundant species, with site densities ranging from 0.1 to 5.3. The parasite was not detected in females. <i>Leishmania infantum</i> seroprevalences of 3.0% and 1.6% were observed in 101 and 126 dog and cat sera, respectively. Although, at this time, the risk of endemic CanL is extremely low, integrated surveillance and prevention measures should be considered.