Schistosomiasis, also known as snail fever, bilharzia, and Katayama fever, is a disease caused by parasitic flatworms called schistosomes. The urinary tract or the intestines may be infected. Symptoms include abdominal pain, diarrhea, bloody stool, or blood in the urine. Those who have been infected for a long time may experience liver damage, kidney failure, infertility, or bladder cancer. In children, it may cause poor growth and learning difficulty.The disease is spread by contact with fresh water contaminated with the parasites. These parasites are released from infected freshwater snails. The disease is especially common among children in developing countries, as they are more likely to play in contaminated water. Other high-risk groups include farmers, fishermen, and people using unclean water during daily living. It belongs to the group of helminth infections. Diagnosis is by finding eggs of the parasite in a persons urine or stool. It can also be confirmed by finding antibodies against the disease in the blood.Methods of preventing the disease include improving access to clean water and reducing the number of snails. In areas where the disease is common, the medication praziquantel may be given once a year to the entire group. This is done to decrease the number of people infected, and consequently, the spread of the disease. Praziquantel is also the treatment recommended by the World Health Organization for those who are known to be infected.Schistosomiasis affected about 236.6 million people worldwide in 2019. An estimated 4,400 to 200,000 people die from it each year.
Bladder cancer diagnosis and mortality are generally elevated in affected areas; efforts to control schistosomiasis in Egypt have led to decreases in the bladder cancer rate. The risk of bladder cancer appears to be especially high in male smokers, perhaps due to chronic irritation of the bladder lining allowing it to be exposed to carcinogens from smoking.In women, genitourinary disease can also include genital lesions that may lead to increased rates of HIV transmission. If lesions involve the fallopian tubes or ovaries, it may lead to infertility. If the reproductive organs in male are affected, there could be blood in the sperm.Urinary symptoms may include:

Blood in the urine - blood is usually seen at the end of an urine stream (most common symptom)
Painful urination
Increase frequency of urination
Protein in the urine
Secondary urinary tract infection
Secondary kidney infectionGenital symptoms may include:

Inflammation and ulceration of uterine cervix, vagina, or vulva
Blood in the sperm
Infertility in femaleKidney function is unaffected in many cases, and the lesions are reversible with proper treatment to eliminate the worms. Neuroschistosomiasis
Central nervous system lesions occur occasionally due to inflammation and granuloma development around eggs or worms that find their way to the brain or spinal cord through the circulatory system, and they can potentially develop irreversible scarring without proper treatment. Cerebral granulomatous disease may be caused by S. japonicum eggs in the brain during both the acute and chronic phase of the disease. Communities in China affected by S. japonicum have rates of seizures eight times higher than baseline.