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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 Leishmania infantum, 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 L. infantum 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. Phlebotomus perniciosus, a potential vector of L. infantum, was the most abundant species, with site densities ranging from 0.1 to 5.3. The parasite was not detected in females. Leishmania infantum 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.

Background The exotic invasive tiger mosquito, Aedes albopictus , appeared in southern Switzerland in 2003. The spread of the mosquito has been surveyed constantly since then, and an integrated vector management (IVM) has been implemented to control its numbers. The control measures focus on the aquatic phase of the mosquito with removal of breeding sites and applications of larvicides in public areas whereas private areas are reached through extensive public information campaigns. Here, we evaluated the efficacy of the IVM. Methods Since all the municipalities with Ae. albopictus in southern Switzerland are currently implementing the IVM, Italian municipalities just across the Swiss-Italian border, where Ae. albopictus is present but no coordinated intervention programme is in place, served as control. Ovitraps and adult female traps were used to measure mosquito abundance in 2019. Generalised mixed-effects models were used to model the numbers of Ae. albopictus eggs and adult females collected. These numbers of Ae. albopictus eggs were compared to the numbers of eggs collected in 2012 and 2013 in a previous assessment of the IVM, using a hurdle model. Results Mean numbers of Ae. albopictus eggs and adult females in 2019 were consistently higher in the municipalities not following an IVM programme. In these municipalities, there were about four times (3.8) more eggs than in the municipalities implementing an IVM programme. Also, the numbers of eggs and adult females increased steadily from the beginning of the Ae. albopictus reproductive season, reaching a peak in August. In contrast, the increase in numbers of Ae. albopictus was much more contained in the municipalities implementing an IVM programme, without reaching an evident peak. Comparison with data from 2012 and 2013 indicates that the gap between intervention and non-intervention areas may have almost doubled in the past 6 years. Conclusions The results of the survey strongly support the efficacy of the IVM programme implemented in southern Switzerland compared to municipalities without defined control measures. With the constant implementation of an IVM, it appears possible to contain the numbers of Ae. albopictus at a manageable level, reducing the nuisance for the human population and the risk of arbovirus epidemics. Graphical Abstract

Background The invasive Asian tiger mosquito ( Aedes albopictus ) poses growing health risks across Europe. In Switzerland, a preliminary field trial was conducted to assess the feasibility of integrating the sterile insect technique (SIT) into existing integrated vector management (IVM), which includes breeding site removal and application of biological larvicides. SIT involves repeated releases of irradiated sterile males, which mate with wild females, producing non-viable eggs and leading to population decline. Methods Following a preliminary release test in 2022, a small-scale SIT trial took place in 2023 in Morcote, Switzerland. Approximately 150,000 sterile males were released weekly over a 45-hectare area throughout the entire mosquito activity season, from May to September. This SIT area also received routine IVM. Population dynamics were compared with a control area where only IVM was applied. Monitoring included egg counts, hatch rates, and adult female densities. Generalized additive mixed-effects models (GAMM) and generalized additive models (GAM) accounted for spatial, temporal, and random effects. Model selection used AIC, BIC, and Chi-square tests (significance at 5%). Results The SIT-treated area showed a significant mosquito population reduction. Egg counts dropped by 57% (GAMM regression coefficient: − 0.8513, P  < 0.001), with temporal patterns differing between SIT-treated and control areas ( P  < 0.001). Egg hatch rates were also lower in the SIT area, with odds of hatching reduced by 1.24 log-odds units ( P  < 0.001). Adult female densities declined by 66% (regression coefficient: − 1.0818, P  < 0.001). Spatial GAMs revealed heterogeneous effects: up to 90% egg reduction in the western release area, while the eastern edge, bordering untreated zones, showed up to 300% higher egg counts. Similar spatial trends were observed for hatch rates and adult females ( P  < 0.01). These findings highlight both the overall effectiveness of SIT and the influence of mosquito immigration on spatial patterns. Conclusions This trial demonstrated the potential of SIT as a complementary tool in Swiss vector control. Public interest and acceptance were high. To improve cost-effectiveness, further optimization of male production, sterilization, transport, and release processes is needed. Continued implementation over multiple seasons is recommended to enhance long-term effectiveness. Graphical Abstract