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Basel-Stadt will continue to fight the Asian tiger mosquito in 2025.
March 17, 2026 - 9:00 AM
News
The Cantonal Laboratory of Basel-Stadt continued its monitoring and control efforts for the Asian tiger mosquito in 2025. It again relied on collaboration with other cantonal agencies, the municipalities of Riehen and Bettingen, and the Swiss Tropical and Public Health Institute. Private households, allotment garden associations, and businesses are urged to continue participating in the control measures to keep mosquito populations as low as possible.
Furthermore, the Cantonal Laboratory detected the dengue virus in a tiger mosquito sample in Basel for the first time during the examination of captured mosquitoes.
The Asian tiger mosquito has been found throughout the canton since 2024. The tiger mosquito is a non-native, invasive species that can potentially transmit pathogens such as the dengue, chikungunya, or Zika virus. Since 2016, the Swiss Tropical and Public Health Institute has been conducting monitoring on behalf of the canton. Most tiger mosquitoes were detected between the beginning of August and mid-September.
In the canton of Basel-Stadt, the authorities and municipalities are responsible for controlling the Asian tiger mosquito in public spaces, while on private property, it is the responsibility of the owners. Since many potential breeding grounds, such as plant pot saucers and rain barrels, are located on private property, the cantonal laboratory provides various informational materials to raise public awareness. It has also inspected the outdoor areas of selected businesses, sensitive properties (e.g., hospitals, retirement homes, schools), and residential buildings. The approximately 40 on-site inspections revealed that in almost all cases, either no measures or only insufficient measures had been taken against the Asian tiger mosquito. Thirty allotment garden associations were also inspected, and deficiencies were found in the majority of the gardens. In 14 associations, plots with a significant number of breeding sites were discovered.
The aim of the control measures is to keep the mosquito population as low as possible so that the quality of life of residents is not increasingly impaired by the nuisance of the tiger mosquito. This also aims to minimize the risk of disease transmission by the tiger mosquito.
Link to the full report on monitoring and controlling the tiger mosquito
The number of mosquito-borne infections has increased across Europe. Chikungunya, dengue, and Zika viruses are transmitted in Europe by the Asian tiger mosquito. The native house mosquito, on the other hand, can transmit the West Nile and Usutu viruses. The Usutu virus primarily infects birds. Because such viral infections are often mild or asymptomatic, they frequently go undetected. To determine the prevalence of such viruses in mosquitoes, the Cantonal Laboratory of Basel-Stadt established a method in 2024 and launched a pilot monitoring program that same year, which it repeated in 2025.
Of the 1,628 mosquitoes captured in 2025, the vast majority were native mosquitoes. Only 2 percent were mosquitoes of the genus Aedes , which includes the Asian tiger mosquito. The mosquitoes were examined in groups (pools). The Usutu virus was detected in 24 of the 163 pools. No other viruses were detected in 2025.
Last year, samples from the 2024 pilot monitoring program were also analyzed using additional methods such as DNA sequencing and by an independent laboratory. This led to the confirmation of the surprising discovery of the dengue virus in an Aedes mosquito pool. This represents the first detection of this virus in mosquitoes north of the Alps. Under the local climatic conditions, this single detection suggests a likely very low prevalence within the local Aedes population, although it does not yet allow for any definitive conclusions regarding the actual distribution.
Link to the full mosquito monitoring report
https://www.bs.ch/news/2026-basel-stadt-bekaempft-auch-2025-die-asiatische-tigermuecke
