Will deadly tiger mosquito invade UK?

Last week, UK newspapers ran scare stories claiming that a killer mosquito 'poised' to invade Britain's shores.

The mosquito the reports referred to was the Asian tiger mosquito which carry the chikungunya virus.

Last year, there was an outbreak of chikungunya virus in Ravenna on Italy's Adrianic coast, where scores of people were infected and one died, said the papers.

European countries including Germany, the Netherlands and France have already reported the Asian tiger mosquito being detected.

Although it has not yet reached the UK, scientists at the Health Protection Agency (HPA) predict Britain may be invaded next, said the papers.

The media referred to a study by the HPA that has found that 'widespread establishment' of the insect is entirely possible in the warm, damp summer conditions of Britain.

The Asian tiger mosquito - so called because of the stripes on its body - can carry chikungunya virus, as well as West Nile virus and Dengue fever.

The mosquito is believed to have spread from Asia to Europe through the international trade in used tyres. The mosquito lays 100 to 300 eggs at a time in water, meaning that small pools of water collected in the tyres can harbour the mosquito eggs and ship them between continents.

Chikungunya virus leaves its victims with a fever that lasts a couple of days. They then go on to suffer from intense headaches, joint pains, rashes and insomnia for days or weeks.

What is the story?

'It's all media hype,' said Dr Phil Luton, a communications officer for the HPA at Porton Down in Wiltshire, which is charged with monitoring dangerous pathogens.

When asked about the study alluded to in the papers, Dr Luton said the last study on the topic by the Porton Down team was published in 2006.

A journalist from a national paper rang asking about the Asian tiger mosquito (Aedes albopictus) and 'since then the story has snowballed'.

Nevertheless, chikungunya virus is a growing problem, and the HPA does have 'some important messages to get out there', said Dr Luton.

Last year, the HPA issued a warning for travellers to be aware of the risk after it noted that the number of cases of chikungunya virus had gone from a typical half dozen cases a year to over 100.

'GPs should be aware of the need to advise people when travelling to exotic locations to take malaria medication and use protection to prevent themselves being bitten,' said Dr Luton.

But what about the threat of being infected with chikun-gunya virus while in the UK?

'It's true that the mosquito could come to Britain and establish itself,' he said 'There aeis a potential risk there and we're keeping an eye on it.'

Despite the HPA being sent matchboxes filled with the remains of mosquitoes that have bitten and not lived to tell the tale, all have so far proven to be the culiseta annulata, a species that is native to Great Britain.

Even if the Asian tiger mosquito does come to the UK, the prospect of an epidemic of chikungunya virus depends on the insects having bitten a carrier first and then spreading the infection.

Dengue fever and West Nile virus are unable to survive in Europe, said Dr Luton. Chikungunya can, as has been shown in Italy. However, the outbreak there only happened after somebody infected with chikungunya virus in India was bitten by an Asian tiger mosquito after they traveled to Italy. The mosquito went on to bite other tourists, spreading the virus.

What do other experts say?

Dr Jo Lines, reader in vector biology and malaria control at the London School of Hygiene and Tropical Medicine, said: 'It's not very likely to happen soon and if it does it's unlikely that we'll see chikungunya transmission.'

This is because the infection will develop in the mosquito slowly in the UK climate, after perhaps three weeks, 'which is a long time in the lives of these mosquitoes,' said Dr Lines.

Additionally, people infected with chikungunya virus are infectious for only a short time.Despite this 'it's worth keeping an eye out for (the mosquito) because if it does arrive the best thing we could do is get rid of the mosquito,' added Dr Lines.

The Asian tiger variety is a vicious daytime biter, a rarity for mosquitoes, and has distinctive black and silver stripes on its body and black and white 'football socks' striped legs, he said.

The slow response in Italy means the Asian tiger mosquito has gone from a local problem to a national one quickly.

Surveillance data from the European Centre for Disease Prevention and Control (ECDC), published in February, called for better mapping of the mosquito across Europe. Since 1975 the mosquito has been seen in several European countries including France, Croatia and the Netherlands.

In the UK, the HPA and the Chartered Institute of Environmental Health run a mosquito watch campaign to monitor any unusual mosquitos.

The ECDC is currently preparing fact sheets for patients, doctors and travellers called the Chikungunya Communications Toolkit.

rachel.liddle@haymarket.com

Mosquito Watch

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