Bassetlaw District Council Statement: Aedes Vexans

We are aware that swarms of mosquitoes identified as Aedes Vexans have become a significant nuisance to the residents of Gamston and Elkesley due to their large numbers and tendancy to bite. We appreciate that this can be unpleasant and have been working with partners including Public Health England (PHE), the Environment Agency, the Coal Authority and local landowners to find a long-term solution to this problem.

Over the last two summers, our Environmental Health Team have been using equipment supplied by PHE Entomologists to capture, identify and count the number of mosquitos at the floodplain at Dover Bottom, where the rivers Meden, Maun and Poulter join the River Idle.

Trials have been conducted to find the effectiveness of a species-specific mosquito larvicide called BTI (Bascillus thurnigiensis israelensis). BTI is a group of bacteria that makes toxins which kill the mosquito larvae when ingested. Trial treatments using BTI have been successful in killing the mosquito larvae, but not the mosquito pupae who do not ingest and so cannot be affected by BTI.

We are working with Public Health England to find the most effective way that BTI can be applied across the affected areas, as a form of control against the Aedes Vexans.

If you are aware of areas on the River Idle, Meden, Mourn or Poulter where flooding occurs on a regular basis then please notify Environmental Health as these areas could be potential breeding grounds where Aedes Vexans may lay their eggs. Please contact the Environmental Health Team by sending an email to

The mosquitos rely on dry ground to lay their eggs and then need floodwaters to start egg growth. Therefore, water management of the affected areas is a priority in tackling this issue and working with the Environment Agency and Drainage Board we will explore what actions we can take to reduce the likelihood of Aedes Vaxans breeding at Dover Bottom and Dover Holt.

Public Health England have stated that currently the mosquito Aedes Vexans does not pose a health threat from disease. They advise:

Aedes vexans is a mosquito that occurs globally, and where it does occur it is an extreme nuisance. In the UK, Public Health England are currently only aware of two notable populations and nuisance biting is only reported from this mosquito in the valley of the River Idle. There is no current evidence of disease transmitted to humans in the UK by mosquitoes. Aedes vexans is not known to be an important disease vector of the most important mosquito-borne diseases in Europe. For concerns over dealing with the prevention and management of bites we encourage people to contact their local PHE health protection team and/or follow the guidance on the PHE website.

Last Updated on Wednesday, April 14, 2021