At the tip of an iceberg: citizen science and active surveillance collaborating to broaden the known distribution of Aedes japonicus in Spain

Eritja, RogerDelacour‑Estrella, SarahRuiz‑Arrondo, IgnacioGonzález, Mikel A.Barceló, CarlosGarcía‑Pérez, Ana L.Lucientes, JavierMiranda, Miguel ÁngelBartumeus, Frederic.  Parasites & Vectors 14 : 375 (2021)  DIGITAL CSIC

Background: Active surveillance aimed at the early detection of invasive mosquito species is usually focused on seaports and airports as points of entry, and along road networks as dispersion paths. In a number of cases, however, the frst detections of colonizing populations are made by citizens, either because the species has already moved beyond the implemented active surveillance sites or because there is no surveillance in place. This was the case of the frst detection in 2018 of the Asian bush mosquito, Aedes japonicus, in Asturias (northern Spain) by the citizen science platform Mosquito Alert.

Methods: The collaboration between Mosquito Alert, the Ministry of Health, local authorities and academic research‑ ers resulted in a multi-source surveillance combining active feld sampling with broader temporal and spatial citizensourced data, resulting in a more fexible and efcient surveillance strategy.

Results: Between 2018 and 2020, the joint eforts of administrative bodies, academic teams and citizen-sourced data led to the discovery of this species in northern regions of Spain such as Cantabria and the Basque Country. This raised the estimated area of occurrence of Ae. japonicus from < 900 km2 in 2018 to > 7000 km2 in 2020.

Conclusions: This population cluster is geographically isolated from any other population in Europe, which raises questions about its origin, path of introduction and dispersal means, while also highlighting the need to enhance sur‑ veillance systems by closely combining crowd-sourced surveillance with public health and mosquito control agencies’ eforts, from local to continental scales. This multi-actor approach for surveillance (either passive and active) shows high potential efciency in the surveillance of other invasive mosquito species, and specifcally the major vector Aedes aegypti which is already present in some parts of Europe.