228 - New strategies for an enhanced integrated control of Aedes albopictus in the city of Heidelberg, Germany.

Abstract: The Asian Tiger mosquito, Aedes albopictus, was first detected in 2007 in Germany at a highway connected via Switzerland to the Mediterranean region which is heavily infested by Ae. albopictus. Since then, the invasive mosquito has spread rapidly in Germany, especially in southwest Germany but also to the north reaching Berlin. Uncontrolled populations of Ae. albopictus, quickly proliferate and can cause tremendous nuisance as well as pose a permanent risk for autochthonous transmission of arboviral diseases. Therefore, the political pressure by residents for the control of this mosquito is high. At the beginning our control strategy was based on two components: a) community participation based on elimination and/or sanitation of breeding sites which can be sustainable but often fails due to lack of commitment of people. b) Door-to-Door control practice including intense information to the residents and applying Bti (Vectobac WG) by trained staff on three-week intervals. This results in high personal costs which amount to several hundred thousand Euros/year just in the city of Heidelberg with about 150.000 inhabitants. Therefore, in 2025, we changed our strategy focusing on making the residents more responsible and controlling the tiger mosquitoes on their own properties by elimination the breeding sites and self-use of Bti-tablets. The campaign was augmented by the wide-scale use of copepods, which were introduced into more or less all mass breeding sites (more than 3000 rain water barrels) in the whole city after the first treatment of Bti. The introduced copepods (Megacyclops viridis) were expected to eliminate newly hatched larvae of Ae. albopictus leading to a sustainable biological control for several weeks and even months. The success of the measures was documented by larval sampling and regularly evaluating the egg counts in ovitraps in the copepod treated and adjacent cities where no copepods are used.