title: Spread and establishment of Aedes albopictus in southern Switzerland between 2003 and 2014: an analysis of oviposition data and weather conditions.
abstract: The Asian tiger mosquito, Aedes albopictus, is a highly invasive mosquito species of public health importance. In the wake of its arrival in neighbouring Italy the authorities of the canton of Ticino in southern Switzerland initiated a surveillance programme in 2000 that is still on-going. Here we explored the unique data set, compiled from 2003 to 2014, to analyse the local dynamic of introduction and establishment of Ae. albopictus, its relative density in relation to precipitation and temperature, and its potential distribution at the passage from southern to northern Europe.
  
  
  
  The presence of Ae. albopictus was recorded by ovitraps placed across Ticino. In addition to presence-absence, the relationship between relative egg densities and year, month, temperature and precipitation was analysed by a generalised linear mixed model.
  
  
  
  Since its first detection in 2003 at Ticino's border with Italy Ae. albopictus has continuously spread north across the lower valleys, mainly along the trans-European motorway, E35. Detailed local analysis showed that industrial areas were colonised by the mosquito before residential areas and that, afterwards, the mosquito was more present in residential than in industrial areas. Ae. albopictus appeared sporadically and then became more present in the same places the following years, suggesting gradual establishment of locally reproducing populations that manage to overwinter. This trend continues as witnessed by both a growing area being infested and increasing egg counts in the ovitraps. There was a clear South-North gradient with more traps being repeatedly positive in the South and fewer eggs laid during periods of intensive precipitation. In the North, the mosquito appeared repeatedly through the years, but never managed to establish, probably because of unfavourable weather conditions and low road traffic.
  
  
  
  Given the present results we assume that additional areas may still become infested. While the current study provides good estimates of relative egg densities and shows the local and regional dynamics of Ae. albopictus invasion, additional parameters ought to be measured to make an objective risk assessment for epidemic disease transmission. The likelihood of Ae. albopictus to further spread and increase in densities calls for continued surveillance.
authors.affiliation: Laboratory of Applied Microbiology, University of Applied Sciences and Arts of Southern Switzerland, via Mirasole 22A, 6500, Bellinzona, Switzerland. eleonora.flacio@supsi.ch.|Laboratory of Eco-Epidemiology of Parasites, Institute of Biology, University of Neuchâtel, Emile-Argand 11, 2000, Neuchâtel, Switzerland. eleonora.flacio@supsi.ch.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Flacio
authors.affiliation: Laboratory of Applied Microbiology, University of Applied Sciences and Arts of Southern Switzerland, via Mirasole 22A, 6500, Bellinzona, Switzerland.
authors.forename: Lukas
authors.initials: L
authors.lastname: Engeler
authors.affiliation: Laboratory of Applied Microbiology, University of Applied Sciences and Arts of Southern Switzerland, via Mirasole 22A, 6500, Bellinzona, Switzerland.|Microbiology Unit, Plant Biology Department, Sciences III University of Geneva, Quai Ernest-Ansermet 30, 1211, Geneva, Switzerland.
authors.forename: Mauro
authors.initials: M
authors.lastname: Tonolla
authors.affiliation: Laboratory of Applied Microbiology, University of Applied Sciences and Arts of Southern Switzerland, via Mirasole 22A, 6500, Bellinzona, Switzerland.|Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, PO Box, 4002, Basel, Switzerland.|University of Basel, Petersplatz 1, 4003, Basel, Switzerland.
authors.forename: Pie
authors.initials: P
authors.lastname: Müller
mesh_terms: D000330:Aedes / Q000033:anatomy & histology / Q000502:physiology*; D000818:Animals; D005260:Female; D007303:Insect Vectors / Q000033:anatomy & histology / Q000502:physiology*; D058865:Introduced Species; D010058:Oviposition; D010063:Ovum; D013557:Switzerland; D013696:Temperature; D014887:Weather