Of Men & Mosquitoes

St. Petersburg, Fla., was an embattled city last week. At night, trucks drove through the palm-lined streets and the stands of scrub pine and palmetto, spewing a chemical fog onto house-and treetops, all the way to the mangrove swamps lining Florida's Gulf coast. Local citizens were fighting, if not on the beaches, at least in the streets and their own backyards, cleaning out every container in which mosquitoes could find enough water to breed. Bird lovers got a stern official warning: stop feeding the birds or putting out water for them.

The alarm was justified but belated. All through August, St. Pete had recorded a gradual increase in the number of cases of St. Louis encephalitis,-- an inflammation of the brain caused by a virus that is carried by mosquitoes. City authorities tried to suppress the news, and were helped by the fact that St. Louis encephalitis, or SLE, is hard to diagnose with certainty. But in late August the number of cases increased until last week there were at least 164 (with 50 proved by laboratory tests) and 13 deaths. Elsewhere in Florida 20 more cases were reported, and a Maryland boy died of encephalitis after a visit to Orlando. 100 miles northeast of St. Petersburg. By then the fever was too high to hide.

Avian Reservoir. The St. Petersburg district had had outbreaks of SLE in 1959 (68 cases) and 1961 (25 cases). The area was known to be seeded with the virus, and a fresh outbreak should have come as no surprise. So far as is known, birds are the main natural reservoir of the virus, which is transmitted from bird to bird, and from bird to man, by mosquitoes. Where St. Petersburg's birds got the virus is uncertain, though Floridians chauvinistically blamed migrants from the tropics. Impartial authorities considered it equally probable that St. Petersburg has by now become a reservoir from which the virus is being carried to other regions. Man is an accidental and usually a dead-end receptacle for the virus. Direct man-to-man infection is unknown.

In the great majority of people, especially the young and healthy, SLE is not a serious disease. It is marked mainly by a short spell of fever and a bad headache. This sort of attack leaves no lasting ill effects. But in a few victims, and especially those over 60, a high fever develops rapidly, the headache is so severe that aspirin and even morphine compounds give no relief; there are chills, nausea and vomiting. Some patients go into a coma or convulsions; if they survive such a severe attack, they may have suffered permanent brain damage. No medicine does any good against the virus of SLE.

The only prescription is the same as for the common cold: rest, quiet and plenty of fluids.

Doused with DDT. St. Petersburg's problem is twofold. With 25% of its residents aged 65 or older (against a national average of 9%), it is full of people who are susceptible to serious cases of SLE. Many of them also love to feed the birds. even to get them to take seed from their lips. At downtown Mirror Lake last week, old folks were feeding pigeons, house sparrows, mockingbirds and grackles. while laughing gulls, ducks and herons splashed in and out of the water. There, in a half-hour, health workers easily caught 70 mosquitoes (Culex nigripalpus, one of the species now known to carry SLE virus) in a small trap. At another lake, irate residents stoned health department workers who were trying to trap ducks merely to draw a blood specimen for virus testing.

The second problem is the choice of mosquito control methods. Like most U.S. cities, St. Petersburg has been doused to a fare-thee-well with DDT, but some mosquitoes survived and multiplied. Spraying kills adult insects but usually not their eggs. The only way to get completely rid of them is to destroy their breeding places. Finally, the city authorities are trying to do just that by cleaning up yards and empty lots, getting rid of old tin cans, coconut husks and automobile tires, and everything else capable of holding stagnant water.

* So called because it was first recognized as a distinct disease, different from other forms of encephalitis, in the 1933 outbreak around St. Louis, when more than 1,130 people became ill and 201 died.

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