ASIA!

Castiglione de Cervia, a village of 2,000 in northern Italy, was celebrating Ferragosto – a summer festival marked by collective rites, eating, drinking and sexual excesses – when one after another fell ill with weeks of high fever, exhaustion and excruciating bone pain.

Within a fortnight, more than 147 people had come down with the same ailment. In time, more cases were reported in the neighbouring towns of Cesena and Cervia. Although the worst symptoms dissipated after two weeks, no doctor could figure out what was wrong. So the locals began to find their own reasons, blaming pollution in the river and denouncing the government. But most of all, they blamed the African immigrants for bringing their diseases to their placid village.

They were right to some extent, for it was soon revealed that the only ones truly commemorating Ferragosto, with their feasts and acts of reproduction, were an immigrant population of tiger mosquitoes.

Originating from the tropical regions of Asia and Africa, the tiger mosquito – characterised by its black and white striped legs and small, black and white body – is also known as the Aedes mosquito. It is a vector for dengue fever in parts of Asia and Africa, also known as chikungunya in Italy and Kerala.

Chikungunya is spread when tiger mosquitoes drink blood from an infected person and, if conditions are right, pass the virus on when they bite again. An investigation by Eurosurveillance, a journal on infectious disease epidemiology, identified the index case to be a foreigner coming from an affected area in the Indian sub-continent who developed symptoms days after his arrival in Castiglione di Cervia that summer.

Aided by global warming and globalisation, Castiglione di Cervia thus became the first in modern Europe to play host to a disease that had previously been seen only in the tropics.

The tiger mosquito is known to occur in a wide range of habitats and conditions, including cold mountainous areas. It is generally more aggressive than indigenous mosquitoes, and is out competing them and replacing native populations. It has become a significant pest in many communities, occupying a habitat that spread from Madagascar eastward to New Guinea, and north to Korea. In 1985, they were found in the southern USA and by 2002 had colonised Nigeria. But it remained in the tropical belt until recent times. It is now present in New Zealand, Eastern Canada, and 12 European countries including France, Switzerland and Spain.

The epidemic in Castiglione de Cervia proved that tropical viruses are now able to spread in new areas, far north of their previous range. Temperatures have claimed as much as four degrees Centigrade higher in the Mediterranean region, and up to two degrees in Scandinavia. It is not unlikely the mosquito's presence will continue to climb latitudes as well as altitudes as the earth heats up.

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