Said to be second only to malaria as the most devastating tropical disease, schistosomiasis (snail fever) affects some 200 million people in seventy-four countries, with half the total cases in Africa and the rest in Asia and South America. The victims of this parasitic worm infection, caused by several species of schistosomes (blood flukes), are often children.
Schistosomiasis is acquired by bathing or swimming in fresh water containing snails that harbor these parasitic flatworms. The flukes multiply within the snails and are released into the water, where they remain until finding a human host’s skin to penetrate. They then travel in the bloodstream and lodge in the bladder or intestines, potentially residing there for many years. Adult flukes lay eggs that can cause inflammation of these organs, blood loss, and bladder cancer.
The most effective approach to dealing with schistosomiasis is avoiding waters containing schistosomes. Once the disease is present in a human, it is most commonly treated throughout the world with praziquantel. This remarkable anthelmintic (parasitic worm–killing drug), effective against all species of schistosomes, was the product of a joint research effort between the Bayer Institute for Chemotherapy and E. Merck, both based in Germany.
Praziquantel (Biltricide, Droncit) is safe, inexpensive (18 cents/dose), and very highly effective when given as a single dose, once a year. It reverses 90 percent of the damage to internal organs caused by the schistosomiasis infection and is also used to treat tapeworm infections, including those caused by ingestion of beef, pork, and fish that are contaminated with tapeworm eggs.
Praziquantel’s uses also extend to animals; it is given in tablet form to treat tapeworm infections in dogs and cats. Used as a topical solution (Profender) in combination with the antiparasitic drug emodepside, it is applied to a cat’s shoulder to treat tapeworm, hookworm, and roundworm infections.
SEE ALSO Carbon Tetrachloride (1921), Hexylresorcinol (1924).
This frontal view of a male schistosoma showing both suckers has been magnified 100x. This parasitic worm is responsible for snail fever, which affects two hundred million people, half of whom reside in Africa.