In Sichuan, human infection with schistosomiasis results from water contact from both domestic water use, such as fetching water and washing clothing, and from work-related contact in various farming activities. Recreational activities like swimming and fishing are also high risk. As shown at right, human and animal stools, which are collected in personal latrines, are carted to field areas, where they are mixed with water and spread on crops as fertilizer. Clinical Manifestations Schistosome penetration of the skin is generally associated with little inflammation, although in a small number of cases repeated infection can lead to the development of a rash known as swimmer's itch. Adult worms settle in the mesenteric veins surrounding the intestine where they cause little to no immediate damage.
Eggs laid by mated pairs of adult worms, however, can cause inflammation and hemorrhaging.
Circulation carries eggs to other parts of the body, specifically the liver and spleen where attack by the body's immune system can lead to development of granulomas and eventually lesions. Occasionally infected people experience a fever, and abdominal pain, enlarged liver and spleen, eosinophilia, and enlarged lymph nodes. Long-term infections can lead to severe development of lesions causing blockage of bloodflow, and portal hypertension which can create collateral circulation that may redirect eggs into other parts of the body including, ultimately, the lungs and brain, where they can be deadly. Symptoms of chronic infection may include general malaise, abdominal pain, headache, enlarged liver, spleen, and lymph nodes, and blood, pus, and mucus in the stool. Cirrhosis may develop as lesions accumulate in the liver.