Monitoring of alien Asian mosquitoes in Linz, Austria

In the last decades, the Asian tiger mosquito ( Aedes albopictus ) and other potentially invasive Aedes species have been expanding their range in Europe. They are considered a major health threat due to their ability to transmit pathogens, such as dengue, chikungunya and Zika viruses. In Austria, Ae. albopictus was first detected in Tyrol and Burgenland in 2012 and was first documented in the Capital City of Vienna in 2020. In Linz, the capital of the federal state of Upper Austria, an intensive monitoring programme was launched in 2024 after Ae. albopictus had been repeatedly detected in previous years. In the summer of 2024 (May-October), ovitraps were set in six locations throughout the city, with five ovitraps in each of the locations. Wooden tongue depressors, which were used as oviposition support, were fixed to one side of a 1 Liter black plastic container, filled with water. The traps were sampled weekly, whereby the oviposition supports were replaced with a new one, as well as the water. Altogether, 640 sampling events took place. Eggs were found in 182 events (30.5 %). In total, 4,876 Aedes eggs were counted. Multiplex PCR resulted in the detection of exotic species Ae. albopictus and Ae. japonicus. Aedes koreicus was not detected. Aedes japonicus were the most abundant, detected in 116 events (63.7 % of the 182 positive events), followed by Ae. albopictus in 59 events (32.4 %). We reported the presence of potential invasive mosquitoes in the city of Linz, Upper Austria. Aedes albopictus eggs were found in the District of Froschberg, near to the City Botanical Garden, and Ae. japonicus eggs in the District of Urfahr, near to the inner City. Our results suggest that both species have an established population in parts of the city.