Grisendi A, D Sgura, M Scremin, M Calzolari, R Veronesi, A Puggioli, M Marinozzi, P Angelini, M Dottori, G Merialdi

Aedes koreicus and Aedes japonicus are invasive mosquito species from East Asia that have rapidly expanded across Italy, particularly in hilly and pre‑Alpine environments. They have been shown to be capable of transmitting certain arboviruses under laboratory conditions; however, their ability to sustain epidemics in natural settings has not yet been demonstrated.
Between March and May 2026, sampling activities targeting the invasive species Ae. koreicus and Ae. japonicus were conducted, complementing previous records collected in 2025. Larval surveys were carried
out in the majority of municipalities located at elevations between 100 and 1,000 meters above sea level in the central-western provinces of Emilia-Romagna.
The highest levels of infestation were recorded in the western provinces, particularly in Piacenza, where 41% of the surveyed municipalities tested positive for at least one of the two species. The proportion of positive municipalities gradually decreased eastward: 39% in Parma, 22% in Reggio Emilia, and 0% in Modena. These findings suggest that the spread of these mosquitoes may have started in Piacenza from Liguria, and subsequently then extended towards the adjacent provinces.
Possible dispersal mechanisms include passive transport along major north–south road networks and aerial dispersal driven by air currents from east to west; however, further investigations are required to confirm these hypotheses.
Ae. japonicus appears to be more uniformly distributed across the surveyed area, whereas Ae. koreicus shows a patchy distribution. In particular, Ae. koreicus was detected in Piacenza and Reggio Emilia, but not in Parma. This pattern may reflect independent introduction events, although additional population genetic studies are needed to verify this assumption.
In the coming years, continued monitoring of the expansion of these species will be essential to assess their rate of spread and to investigate potential mechanisms of adaptation to local ecosystems and climatic conditions.