Snail Fever (Schistosomiasis) Strikes China

DOCTOR'S VIEWS ARCHIVE

BEIJING (September 10, 1998) -- According to the Chinese Red Cross, there are outbreaks of a number of diseases including snail fever in the vast flooded area along the Yangtze River. Nearly 10,000 medical teams are giving out water purification tablets and treating people who have had contact with polluted flood water and so are at risk for getting snail fever, or schistosomiasis.

Snail fever, or schistosomiasis, is a parasitic disease of the liver, gastrointestinal tract and bladder. The disease is caused by a specific worm which enters a person's body from infested polluted water.

There are three main species of these worms (flukes)-- Schistosoma haematobium, S. japonicum, and S. mansoni -- which cause disease in humans. The larval (young) forms of the parasitic worm live in freshwater snails. Hence, the name "snail fever."

The life cycle of these parasitic worms is complex. A form of the parasite (the cercaria form) is liberated from the snail. It burrows into a person's skin. There it transforms to another stage (called the schistosomulum stage). It then migrates to another location -- the urinary tract (S. haematobium), the liver or intestine (S. japonicum, S.mansoni) -- where the adult worms develop.

Eggs are shed by the adult worms into the urinary tract or the intestine and hatch to form miracidia (yet another form of the parasite). When these are eliminated outside the human body, they then re-infect snails, completing the life cycle of the parasite.

Adult schistosome worms cause very serious tissue damage inside the human body. Other Schistosome species which cannot live inside of man still cause a skin condition known as swimmer's itch.

Schistosomiasis is also called "bilharzia" after the 19th-century German physician Theodor Bilharz (1825-1862).

The term "schistosomiasis" came from Greek roots -- "schisto-", split or cleaved + "soma", body = cleft body. The cleft body refers to the deep cleft that runs the length of the male worm's body. It is in this groove that the slender female worm is held during copulation.

The floods in China this year have killed more than 3,000 people and now threaten to sicken many more with snail fever.