A Drug for Snail Fever

The squishy little parasites are less than an inch long, but they cause a globe-girdling disease variously known as schistosomiasis, bilharziasis, or simply snail fever. The more man does to increase his food supply, the more he nurtures the parasites and spreads the disease. Only a few years ago, the world had an estimated 100 to 200 million schistosomiasis victims spread across much of Asia, Africa and Latin America; now the estimate is 50% higher, largely because new irrigation canals and other waterworks have enlarged the parasites' habitat.

All this assures a ready market for he new drug just announced by Switzerland's Ciba Ltd. Called Ambilhar, it is he first drug capable of curing schistosomiasis without making the patient sicker than he was to begin with.

Schistosoma parasites hatch in water, then have a complex life cycle: they enter the body of a snail, progress to a second larval form, then emerge and enter the human body either by mouth or through the skin. In man they cause a lifelong debilitating disease marked by coughs, rashes, blood in the urine, fever and nausea; eventually they attack the liver, lungs, spleen and brain.

So far, the use of copper sulphate to kill the carrier snails has been ineffective. Some of the drugs now being used to treat the disease require painful injections. In 90% of cases, Ciba's Ambilhar pills cure the American and African forms within a week; tests on the Asian form are under way. Yet, as Ciba admits, even this potent drug cannot wipe out the disease because a cured patient who goes back into the rice fields may be reinfected within minutes.

Malaria has been sharply curbed by improved drugs and anti-mosquito spraying. Now that schistosomiasis itself can be cured, the next step is to clean up water supplies. Combined cure and prevention might then halt the relentless spread of the fever, which is now close to surpassing malaria as a destroyer of human health in the tropics.

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