Schistosomiasis is a parasitic disease that affects a wide range of tissues and organs, including the gastrointestinal tract, ureter, liver and spleen. Its clinical manifestations can vary considerably, depending on the location of the adult worms. The infection can be either acute or chronic. Acute schistosomiasis is characterized by fever, abdominal tenderness, cough and general malaise. Chronic schistosomiasis is characterised by abdominal pain, diarrhoea and/or frank blood. However, a significant proportion of patients are asymptomatic at the time of the initial infection.
Intestinal schistosomiasis is caused by the eggs of the schistosomula, which enter venous and arterial blood vessels, mainly in the mesenteric veins of the bowel and liver. Clinical manifestations are primarily abdominal and urinary, but can also involve skin, spleen, spinal cord and brain. Symptoms may develop within a few weeks of the initial infection or occur several months later. If they do develop, a tissue biopsy should be carried out to obtain an accurate diagnosis.
The schistosomula have two major reproductive organs, the male and female. They lay eggs in different sites, which vary with species. These eggs are excreted in feces, urine or stool samples. When these eggs clog the ureters, hydronephrosis is likely. This can lead to severe uremia and/or hematemesis. Other complications include portal hypertension, which can cause oesophageal varices. Depending on the type of fluke, neuroschistosomiasis can develop, which is characterized by focal neurologic symptoms, such as seizures.
There are three major species of schistosomes that can cause infections: Schistosoma japonicum, which is common in the Far East and South America; S. guineensis, which is common in sub-Saharan Africa; and Schistosoma mansoni, which is found in South America and sub-Saharan Africa. Besides causing gastrointestinal diseases, the infection can also affect the liver and spleen, resulting in liver fibrosis and hepato-splenic schistosomiasis.
Acute schistosomiasis occurs in approximately 5 to 10 percent of infected populations. While most of the infected people are asymptomatic at the time of infection, about 5% will experience a more severe, chronic infection. Although schistosomiasis is generally reversible after treatment, persistent symptoms can be serious. To diagnose schistosomiasis, a colonoscopy or tissue biopsy should be performed. An alternative diagnosis might include inflammatory bowel disease, which is characterized by the presence of large, red, ulcerated patches on the colon’s surface.
Schistosome infections can be life-threatening, especially if they are not detected and treated early. Treatment may require the removal of the worms and their eggs, but in many cases, the infection will clear up on its own. After a period of about three to six weeks, most people can resume normal activity. But it is important to avoid contact with contaminated water, such as lake waters, and to avoid swimming in freshwater bodies. During treatment, it is recommended that the infected individual remain on a low-calorie diet and limit exercise, as the symptoms of the infection are associated with undernutrition.
Acute schistosomiasis may result in a severe clinical course, whereas chronic schistosomiasis is more common. Acute schistosomiasis can be fatal.
