Press release: Mosquito treatment in Ashford, Kent

Action was taken to eradicate eggs and larvae of an invasive species of mosquito, Aedes albopictus (Asian tiger), which has become more common in Europe during recent years. Though the mosquito poses no immediate risk to public health, the decision was to treat the area and prevent it becoming established in the UK.

PHE and Ashford Borough Council have ensured residents and businesses in the area have been fully informed of all treatment taking place and both agencies are working closely with Kent County Council.

The eggs and larvae were discovered through PHE’s ongoing mosquito surveillance programme which monitors 30 UK ports and airports. Since invasive mosquitoes became more widespread in France, surveillance has been conducted by PHE at motorway service stations in south east England on the main routes from the south coast ferry ports and Eurotunnel.

Dr Jenny Harries, Deputy Medical Director at Public Health England, said:

PHE operates a surveillance system to monitor mosquito species and check for any that are new to the UK.

Through these activities we identified a small number of eggs and larvae from the Aedes albopictus (Asian tiger) mosquito in traps at Ashford International truck stop. Enhanced monitoring of the area was carried out and no further evidence of this mosquito has been found.

As a precaution we advised the local authority on measures to eradicate the mosquito and remove any suitable habitats in the area. We will continue to monitor the situation closely through our surveillance system. There is no immediate risk to public health in the UK.

We are also grateful to the truck stop for their cooperation and support as a responsible business.

This is the second time this species has been found in the UK, and is likely to have resulted from the importation of one adult female across the Channel via vehicular traffic. A similar discovery was made by PHE in Folkestone last September. Adult mosquitoes can only fly a very short distance and so control measures are implemented up to a 300 metre radius.

The presence of a mosquito does not mean that it is carrying any diseases as they first need to bite an infected person and then move on to infect a second individual. There are currently no cases of diseases known to be carried by this mosquito circulating in neighbouring countries and therefore no risk to health locally.

Andrew Scott-Clark, Director for Public Health in Kent added:

This has been a great example of close working between local government and Public Health England to safeguard people in Kent.

The surveillance system has been highly effective in detecting this invasive species and enabled a swift response from Ashford Borough Council to treat the site and ensure this species does not become established.

Having been consulted throughout, I can assure people in Kent that this poses no current risk to the public’s health.

PHE and Ashford Borough Council will continue to monitor the site for any further signs of invasive mosquitoes and ensure there are no suitable habitats.

PHE has run a surveillance system with partners (Port Health Officers and Edge Hill University) since 2010. This now includes surveillance at more than 30 UK sea and airports and at the largest used tyre importers. Since invasive mosquitoes have become more widespread in France, surveillance has been conducted by PHE at motorway service stations in the south east of England on the main routes from the south coast ferry ports and Eurotunnel (since 2014). The surveillance system combines a number of traps that detect mosquito eggs, host-seeking and blood-fed mosquitoes and larval sampling.

PHE have also run a mosquito recording scheme since 2005, receiving mosquitoes from the public and environmental health for identification. PHE encourage the public to continue to submit mosquito samples for identification through a collection scheme. Please note, all samples returned by the public are of native mosquito of which there are known to be more than 30.

Aedes albopictus (A. albopictus)

Limited ability to fly

The species has low ability to fly and therefore the focus for control measures needs to be across a 300 metre radius area around the truck stop. There are fewer than 10 residential properties in the area and we have made contact with all of the households and are working to remove aquatic habitats found at these properties.

These findings indicate individual mosquitoes that have travelled into the UK via traffic, and laid eggs.

There is no indication of the source of the mosquito eggs captured at the site but given the location, importation of an adult mosquito by a vehicle arriving from Europe entering through one of the ports is the most likely route. As a precaution, we have recommended that local authorities take steps to remove potential mosquito breeding grounds in the area.

There is no indication this mosquito is carrying any virus that is a risk to human health.

Low risk to the public

As a result of PHE’s surveillance network we were able to identify the mosquitoes and take prompt action to eradicate them at an early stage. We will monitor the situation closely to ensure no further mosquito eggs or larvae.

Characteristics of an A. albopictus mosquito

This is a small mosquito with characteristic black and white striped legs, a white line on the thorax, and black and white markings elsewhere on the body. It is easily confused with a native species that is much larger, and also has similar markings. More information can be found on this at the PHE website.

No evidence of disease risk

The presence of a mosquito does not mean that it is carrying any diseases. For an A. albopictus mosquito to carry a virus, it needs to first bite an infected person. Incidences of this in Europe are not common and there have only been a few instances of dengue and chikungunya in Southern Europe and only where the mosquitoes are established.

There is currently no evidence to suggest A. albopictus is established in the UK.

There is no evidence to suggest that Zika can be carried by A. albopictus. It has been implicated in the transmission of other viruses like dengue and chikungunya.

First find in 2016

Mosquito eggs found in one trap near Folkestone were confirmed as A. albopictus on 30 September 2016. This was the first detection of this non-native mosquito species in the UK. Enhanced surveillance was implemented. There was no further evidence of them at the Folkestone site despite extensive surveillance.

Surveillance helps prevent invasive species establishing

A. albopictus has shown an ability to adapt to its environment and can lay diapausing eggs that survive winters in temperate areas, which means they can ‘hibernate’ and hatch the following spring.

Following the first detection, all other traps at the location were re-surveyed and found to be negative.

Enhanced surveillance is being conducted at the site and in the vicinity, including the deployment of additional traps and larval sampling. So far, no further evidence of A. albopictus has been found, and there is no evidence so far that it has become established.

Image courtesy of James Gathany via CDC Photo library.