Tiger mosquito: Swiss government unveils further measures

Tiger mosquito: Bern unveils further measures Keystone-SDA

To combat the tiger mosquito, Switzerland intends to supplement its existing strategy with measures that directly target adult insects. The government set out these measures in detail on Friday, in response to a postulate.

The motion tabled by parliamentarian Sarah Wyss called, in particular, for new species to be rigorously combated as soon as they appear, and for federal support for projects based on the latest scientific knowledge regarding the control of the tiger mosquito.

Taking the view that the requests concerning the government’s responsibilities had already been addressed, the government outlined the current status of the three complementary techniques. It began with mosquito traps combining carbon dioxide and other attractants, which are used to lure adult tiger mosquitoes in order to reduce their numbers locally.

While acknowledging that this approach is effective when the traps are deployed on a large scale, the government pointed out, however, that questions remain regarding the actual density of the traps, their distribution, the long-term impact of captures and the influence of local socio-economic conditions on the effectiveness of this approach. The Swiss Tropical and Public Health Institute, in collaboration with the University of Basel, is investigating some of these issues as part of the TIGER 2.0 project.

Targeting the eggs

The other two approaches being tested aim to limit the spread of the tiger mosquito by targeting its offspring. Known as “sterile insect technique (SIT)” and “incompatible insect technique (IIT)”, these methods involve introducing a sterile male or a male carrying a bacterium to curb the species’ reproduction.

As well as being environmentally friendly, SIT can reduce tiger mosquito populations by a further 60-70% if implemented rigorously. However, this figure can be achieved only if the technique is combined with traditional control methods.

The government notes, however, that TIS is “significantly more complex to implement and approximately three times more expensive than integrated vector control”. In Switzerland, the production of sterile males is currently under investigation and could become operational by 2027–2028.

TII offers greater potential for effectiveness than TIS. It is mainly used in regions where diseases transmitted by the tiger mosquito are, unlike in Switzerland, very widespread.

Another limitation is that the bacterium used is already present in tiger mosquitoes in Switzerland – at least in Ticino – so it is highly likely that local populations have developed resistance to this bacterium. Furthermore, its ecological impact is difficult to assess. The government does not yet favour this approach in Switzerland, but it could be an option for the future following the successful implementation of TIS.

A two-phase plan

These measures are intended to complement the two priority areas of action. In cantons where the tiger mosquito is not yet present or has only been observed sporadically, it is recommended that any detected breeding sites be eradicated.

In cantons where the tiger mosquito is already well established (phase 2) or where imported cases of disease have been detected (phase 3), the priority is to step up vector control, in particular through the application of larvicides, the government said.

Reports of tiger mosquitoes have risen steadily in Switzerland in recent years. In 2025, a total of 2,639 reports were recorded, of which 2,537 (96%) were valid. Of these, 774 (31%) involved tiger mosquitoes. The regions most affected are Geneva, Basel and Ticino.

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Translated from French, reviewed by an English Department journalist.