Pathology and diagnosis of Schistosomiasis

Pathology
Disease pathology is caused by the body’s immune response to antigens coating the eggs circulating the body. The disease covers a range of clinical symptoms according to species. Two main forms of human schistosomiasis are recognised, both with differentially associated pathology: urogenital schistosomiasis, resulting from infection by S. haematobium, affects over 112 million people in sub-Saharan Africa and is associated with haematuria, bladder damage, hydronephrosis with a risk of progression to severe disease such as kidney failure and bladder cancer.  Intestinal schistosomiasis in sub-Saharan Africa is mainly caused by infection with S. mansoni, estimated to be the cause of bloody diarrhoea in 4.4 million people, and hepato-splenomegaly, a severe clinical manifestation of the disease is estimated to affect 8.5 million people. In Aisa, S. japonicum is the main causal agent of intestinal schistosomiasis.

Diagnosis
The usual procedure to diagnose schistosome infection is microscopy. Stool and/or urine samples are collected from the patient and microscope slides are prepared using filtration or smearing techniques which are examined for the presence of schistosome eggs. If evident, the eggs are counted as an estimate of worm burden, termed infection intensity. For stool samples, this technique is known as Kato-katz, and a stain is often used for the eggs. Other diagnostic tests include the circulating cathodic antigen CCA test for S. mansoni and hemastix dipstick test for presence of hematuria for S. haematobium infection. Both allow the potential for quick identification of infection from a urine sample.