SHISTOSOMIASIS OR BILHARZIA

This disease was well known to me when I worked in Africa. In Kenya, we were aware that our children needed to avoid swimming in "still" water as lakes and ponds often had the intermediate host snail. In Egypt, one of our Sudanese workers was often sick – suffering from this liver fluke which he had contracted earlier in his life. When I was in Sudan, I prayed that I would not contract this disease as I baptized new converts in a number of locations where the water may have been infected.


Greenwald B., (2005)Gastroenterol Nurs. 2005 May-Jun;28(3):203-5
Schistosomiasis ranks second, behind malaria, among human parasitic diseases in terms of public health and socioeconomic importance in tropical and sub-tropical areas. Worldwide, 1 of 30 people has schistosomiasis. Up to 300 million people are infected, and 600 million live in environments where infection is a risk. Tourists from non-endemic areas are contracting schistosomiasis due to the rise in "off-the-beaten-track" tourism.

The best information on the worldwide situation is from a report by the World Health Organization found at this site:

http://www.who.int/wormcontrol/wer8116.pdf

Transmission cycle
Causal agents of the disease are fluke worms (schistosomes). Their eggs leave the human body in urine (in urinary schistosomiasis) or faeces (in intestinal schistosomiasis), hatch in water and liberate larvae (miracidia) that penetrate into freshwater snail hosts. After several weeks, cercariae emerge from the snails and penetrate the human skin (during wading, swimming, washing). Cercariae develop to maturity within the body and subsequently migrate to the lungs, the liver, and the veins of the abdominal cavity or the bladder plexus. Eggs escape through the bowel or urinary bladder.