Snail's Plague

The disease is as old as the pharaohs -telltale traces remain in mummies 3,000 years old--but to the dismay of public health doctors, it is more prevalent than ever. Schistosomiasis, bilharziasis, snail fever--by whatever name, the debilitating and often fatal illness afflicts more than 150 million people in Africa, Latin America and Asia. The disease is almost unknown in the U.S.; the few scattered cases brought into the country each year by visitors and immigrants fail to spread, create no public problem.

Cause of all the trouble is a wiggly tailed, microscopic larva that lives out its life as an unwelcome hitchhiker in both snails* and man. Hatched in fresh water, the schistosomal larva must invade a snail within about 24 hours or die. After weeks of development and change in the snail, the larvae move on and burrow into a human body, where they mature and mate in the bloodstream. Then they settle down to years devoted to depositing eggs in vital organs. The adult parasites live in an almost constant state of copulation and the female can produce up to 3,000 eggs a day for as long as 30 years. Once the eggs enter the bladder and intestines, they are passed out of the body and, in areas of primitive sewage disposal, they reach fresh water, hatch and start a new cycle.

Paddies & Patches. With such an intricate career a parasite would seem vulnerable to several forms of attack. But the only known drug treatments for humans are rugged and not particularly reliable once the disease reaches an advanced stage. In many parts of the world, schistosomiasis is so much an accepted plague of life that the abdominal pain it causes, the blood in the urine and feces, often are disregarded until too late. After years of apparent health, a victim's abdomen may swell as he gradually grows weak and dies, his liver, lungs, urinary tract or even his heart damaged beyond hope from the irritation caused by thousands of parasite eggs.

Eradication of parasite-bearing snails is not one bit easier than attacking the worms in man. The snails have survived the assaults of modern chemistry, and they thrive on the benefits of modern engineering--each new irrigation system, each new dam provides more breeding places. Victims pick up the larva in snail-infested paddyfields and irrigated patches where they work, drink and wash clothes. During the occupation of Japan, the U.S. Army drastically reduced the incidence of the disease by killing snails with the chemical sodium pentachlorphenate, but like so many other chemical agents, the stuff also killed fish and other water life.

Chemical Attack. But an acceptable anti-snail chemical still seems the most promising solution to the old plague. At field stations in Africa, World Health Organization experts are busy testing dozens of compounds prepared in the laboratories of private industry. After screening 5,000 compounds in search of one that kills snails but leaves other stream life unharmed, Shell Oil researchers in Britain reported that they may finally have discovered the chemical the world has been waiting for. One pound of the stuff per acre of water kills snails within 15 minutes by attacking their respiratory system. According to company claims, it is "relatively innocuous" to other forms of animal and plant life.

The compound will undergo extensive WHO tests, and if the new chemical is indeed everything that is claimed, snail eradication can begin in earnest. And none too soon. "Today," warns the British medical journal Lancet, "schistosomiasis threatens to replace malaria as a major scourge of mankind."

-Not the edible Helix pomatia made savory with garlic and butter.

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