Rome, like many other parts of Italy, is under attack from tiger mosquitoes, a particularly aggressive and dangerous species believed to have arrived from Asia.

Paul Reiter, head of the entomology section of the CDC Dengue Laboratories in Puerto Rico, who discovered the first specimens in the US in 1983, said Aedes albopictus had spread to the world in recent years courtesy of the worldwide trade in second-hand tyres.

The bite of Aedes albopictus is painful, and it carries the danger of potentially lethal anaphylactic shock and, theoretically, even encephalitis. The species has been implicated in the rise of dengue and in outbreaks of West Nile virus.

Enrico Alleva, former professor of ethology and now director of the National Health Institute's department of behaviour pathophysiology, spends most of his time advising local and health authorities on how to wage war on the pests.

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Thousands of Romans have been bitten, scores turn up daily at hospitals for emergency treatment. The city is spending more than Pounds 1.5 million spraying suspected breeding grounds, mainly stagnant water, with insecticide. Posters, radio and TV warn Romans to eliminate pools of stagnant water.

During the first known infestation in Rome, in 1999, mosquito-eating goldfish were introduced to the city's fountains.

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Professor Alleva said: "Aedes albopictus was first noticed in the harbour cities of Genoa and Civitavecchia five or six years ago. We believe they, or their larvae, arrived with shipments of tyres, in the water that accumulates inside the tyres.

"Since their arrival in Rome three or four years ago, they have increased in number and spread from outlying areas near pools of stagnant water to the whole of the city."

Professor Alleva said that the mosquito's natural enemies, such as bats, birds and small reptiles, are becoming rarer because of habitat loss and other factors.

"With the globalisation of trade, the number of travelling insects has increased. We must make the environment capable of combating them," he said.

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Paul Bompard