Pathogenesis of schistosomiasis.

Schistosomiasis is caused by fluke worms that are in the blood. Adult schistomes are worms which can be between 7 to 20mm long and have separate sexes.

The female schistomes can produce up to thousands of eggs daily which contain ciliated miracidium larva. These eggs are excreted by an infected person through the urine and faeces. The eggs then look for the transitional host, which are freshwater snails.

After the eggs have infected the snails the ciliated miracidium larva begin to multiply into cercarial larvae that then leave the snail after 4-6 weeks. These cercariae then search for the skin of the human host.

Once they have found a human host, they penetrate the skin and enter the circulation. After this they move to the lungs and eventually the liver where the cercariae can develop into the young worms or schistosomulae by feeding of the red blood cells of the host.

After this development the worms can migrate to around the bladder or around the intestine to continue the process.

When eggs pass through the body of the host, they cause damage to the organs they migrate through. When this happens, the body tries to repair this damage and this causes granulomas. Over long term infection, these granulomas gradually increase which can cause the organ to not function properly.




Diagnosis occurs through microscopic analysis of the faeces and urine of the sufferer. It is common practice to examine three or more specimens. In hospital settings cystoscopy, endoscopy and radiography can examine the extent of lesions and granulomas in the intestine and bladder.

(Gryseels et al., 2006; Bottone, 2006.)

True-False Question
Please complete this short true or false quiz after reading this section to test your knowledge on schistosomiasis.

1. Schistomes have only one sex

True False

2. Once cercariae have penetrated the skin of the human host, they move to the lungs and then the liver to develop.

True False

3. Damage is caused to organs by the eggs passing through the body.

True False