Blood suckers

Mosquito: the story of mankind's deadliest foe

Andrew Spielman and Michael D'Antonio <em>Faber and

Every 12 seconds a child dies from malaria. Almost half a billion people contract the disease annually and a couple of thousand bring it back to the UK after trips abroad. Which means that there are, more or less, as many new cases of malaria diagnosed here every year as there are of Aids. And yet malaria remains a disease of others, of elsewhere.

This was not always so. Malaria was endemic in southern England until the early part of the 20th century. Oliver Cromwell died of the disease. He could have been saved, because a cure for malaria was available in the 17th century. Sadly for Cromwell, the drug was a powder derived from the South American cinchona tree, channelled to Europe via Catholic Spain. The Lord Protector had no access to this so-called "Jesuits' powder" and his fate was sealed. Today, we know that the powder contained quinine, which remains among the most potent of known anti-malarial compounds.

The word malaria means "bad air", because it was long known that the disease was contracted near swamps. It was only at the end of the 19th century that the British physician Sir Ronald Ross noted that mosquitoes carried the tiny blood-dwelling parasites that cause malaria. Mosquito larvae thrive in stagnant swamp water, so draining swamps deprives malaria-carrying mosquitoes of their reproductive environment.

Drainage schemes led to the eradication of malaria from most of western Europe and the United States by the Fifties. The disease remained, however, in parts of the Far and Middle East, South America and Africa, where today 90 per cent of the world's cases are found. Economics, rather than climate, determines whether malaria prevails in a given locality.

The Harvard economist Jeffrey Sachs postulates that malaria contributes significantly to economic malaise. The disease - whose symptoms have been modestly described as flu-like, only ten times worse - flattens many African workers several times a year, as well as disrupting children's education and development. Sachs has calculated that eradicating malaria from a country in which the disease runs at epidemic levels would stimulate economic growth by 3.2 per cent a year.

That, then, is malaria: a disease transmitted by the bite of hungry female mosquitoes, looking for blood to nourish their eggs; a disease affecting hundreds of millions of people, which causes economies to stagnate and kills babies. And yet, malaria, like most tropical diseases, fails to trouble most of the world's more affluent inhabitants, so long as they are discerning in their choice of holiday.

Two summers ago, however, an odd thing happened in the US. Birds up and down the East Coast started falling out of the sky. Soon afterwards, a few human beings started reporting unusual fevers in New York City, and six people died. It turned out that they had contracted mosquito-borne "West Nile" virus, which inflames the brain. Mosquito-fear gripped America. Squadrons of helicopters were mobilised to spray insecticide over large areas of Manhattan, as New Yorkers contemplated being bitten to death. The outbreak eventually ran its course, as the long hot summer drew to a close and the mosquitoes disappeared.

The panic of Americans, triggered by a few deaths on their own doorstep, inspired Spielman and D'Antonio to write a book about mosquitoes and the bugs that they carry. They have done a good job. We learn about the nature of some of the 2,500 different species of mosquito and about West Nile virus, malaria and other diseases, including yellow fever, dengue and elephantiasis, that are carried by mosquitoes.

The complacency of the west over infectious diseases is revealed to be the folly we always knew it was. The US may have drained its swamps, but the four billion worn tyres that litter the American landscape accumulate rainwater, which provides the perfect habitat for the propagation of these tiny vampires. A global trade in used tyres carries mosquitoes, and the diseases they harbour, around the world.

Environmental issues are never far from the forefront of dealings with mosquitoes. DDT spraying campaigns wiped out mosquitoes from many areas in the Fifties, which all seemed rather impressive until Rachel Carson, in Silent Spring, noted the collateral environmental damage associated with indiscriminate use of insecticides. Whatever the rights and wrongs of mosquito control, the apparently endless march of malaria, and the emergence and re-emergence of insect-borne diseases throughout the world, paint a clear picture. We ignore contagion at our peril.

Dr Michael Barrett is a lecturer in tropical medicine at the University of Glasgow

This article first appeared in the 30 July 2001 issue of the New Statesman, So what tribe do you belong to?