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snail fever,parasitic disease caused by blood flukes, trematode worms of the genus Schistosoma. Three species are human parasites: S. mansoni, S. japonicum, and S. haematobium. The disease is prevalent in Asia, some Pacific islands, Africa, the West Indies, South America, Spain, Puerto Rico, and Cyprus. The larvae of the parasite are harbored by snails, which serve as intermediate hosts, and infect humans who bathe in or otherwise come in contact with infested waters. The larvae enter through the skin, migrate via the blood vessels, and mature in the lungs. From there they travel to the veins of the upper or lower intestine or bladder and reproduce. Some eggs pass out in the feces. Others are carried into the liver, where the body surrounds them with white blood cells, forming hundreds of tiny ball-like granulomas that eventually impair the liver's ability to function. It is believed that the flukes settle in blood vessels that have a particular human immune substance, tumor necrosis factor, that they require in order to reproduce.
The disease is characterized by a skin eruption at the site of entry, fever, diarrhea, and other symptoms, depending on the tissues affected; cirrhosis of the liver is common. The disease can be cured with the drug praziquantel, but reinfection can occur. Although symptoms vary according to the species of infecting fluke, all forms can result in general weakening and eventual death. Control of the disease is difficult, but control of the snail populations that serve as intermediate hosts is effective in reducing the incidence of the disease. Proper sanitation and disposal of human wastes are also important.
a disease of the urinary tract and intestine caused by parasitic worms—trematodes of the family Schistosomatidae. It was originally called bilharzia after the German physician T. Bilharz, who discovered the causative agent in 1851.
any one of several diseases of humans and animals caused by helminths of the family Schistosomatidae of the class Trematoda.
Schistosomiases of humans occur mainly in tropical countries. The causative agents belong to the genus Schistosoma, whose females deposit eggs in the small blood vessels of the urinary bladder and intestine. After entering these organs, the eggs are excreted with urine or feces. Larvae (miracidia) emerge from the eggs after they reach water and are ingested by mollusks, in which they reproduce and develop. The cycle is completed with the emergence of larvae with tails (cercariae) in the water. The cercariae penetrate the human body through the skin and mucous membranes. Individuals become infected after working or swimming in bodies of water contaminated by the urine and feces of persons suffering from schistosomiasis or after drinking water from such bodies of water.
Skin rashes, itching, and sometimes fever occur in the early stage of schistosomiasis. If the genitalia and intestine are affected (bilharziasis), the patient feels a sharp pain upon urination, the urine becomes tinged with blood, and chronic colitis, with mucus and blood appearing in the feces, develops. Schistosomiasis is treated with antimony agents, for example, Anthiomaline (or anthiolimine); it is also treated with Ambilhar (or niridazole). The disease can be prevented by protecting lakes and streams from pollution, by banning swimming in stagnant or slow-flowing water in areas where schistosomiasis is endemic, and by boiling drinking water or filtering it through cloth.
N. N. PLOTNIKOV