Mosquitoes 'could bring exotic diseases to UK'

More rainfall and warmer temperatures could provide ideal conditions for the Asian tiger mosquito in the UK

Mosquitoes could bring diseases such as dengue fever and West Nile virus to the UK within the next few decades, experts are warning.

Writing in The Lancet Infectious Diseases journal, they said warmer UK temperatures could make conditions favourable for the insects to breed.

However, climate change is just one of many factors in the spread of diseases.

Public Health England said it had been monitoring places where mosquitoes like to lay eggs, such as used tyres.

Scientists from the emergency response department at Public Health England, who wrote the report, said there were already 34 different species of mosquito in the UK.

In some parts of Europe, mosquitoes and ticks - which carry particular diseases transmitted by biting insects - are on the rise.

Over the past decade, for example, malaria has spread to Greece, the West Nile virus to eastern Europe and a disease called chikungunya to Italy and France.

Mosquitoes and ticks are known to be highly responsive to changes in temperature and rainfall.

Climate modelling

The report said warmer temperatures in the UK in future could provide ideal conditions for the Asian tiger mosquito (Aedes albopictus), which spreads the viruses that cause dengue and chikungunya.

Using climate change modelling, the report predicted that the seasonal activity of ticks, mosquitoes and parasites could increase if temperatures increased by more than a few degrees - particularly in southern England.

But since such a rise cannot be accurately predicted, the report conceded that the direct effects of a climate change could not be predicted confidently either.

The British climate is already suitable for the transmission of West Nile virus, which can be spread by several mosquitoes currently found in the UK - but there have been no human cases so far.

Dr Jolyon Medlock, joint author of the report and head of medical entomology at Public Health England, said all invertebrates were affected by changes in temperature.

"They develop faster at higher temperatures so during a mild winter they won't be killed off.

"In summer they will then be more abundant, although dry summers are not good for mosquitoes.

"But they can survive in water butts in gardens."

Used tyres

He said mosquitoes often laid their eggs in places which had become flooded.

Those species originating in Asia have probably been imported into the UK through the global trade in used tyres.

These tyres can often be transported large distances along motorways, moving the eggs to new habitats and environments.

Dr Medlock said that although no non-native mosquitoes had been detected in the UK so far, "a better system to monitor imported used tyres needs planning".

He said Public Health England had been conducting surveillance at seaports, airports and some motorway service stations.

The report underlined the fact that climate change was not the only factor influencing the increase in vector-borne diseases in the UK - just one of many.

Other factors include urbanisation, land use change, migration and globalisation.

However, the authors emphasised the need to assess the risks and prepare for future outbreaks.