http://www.histopathology-india.net/Schisto.htm
Schistosomiasis (bilharziasis) is a parasitic infection caused by blood flukes (Trematodes).
Three main species cause human infection: 1. Schistosoma haematobium, ; 2. Schistosoma mansoni ; 3. Schistosoma japonicum.
Epidemiology: Existence of Schistosomiasis about 5000 years back is evidenced from the DNA studies of Egyptian mummies . Schistosomiasis is increasing in prevalence, affecting nearly 10% of the world’s population and ranking second only to malaria as a cause of morbidity & mortality.
S. haematobium are found in tropical Africa & part of southwest Asia.
S. mansoni are found in tropical Africa, part of southwest Asia, south America & Caribbean islands.
S. japonicum are found in parts of Japan, China, Philippines, India & part of southeast Asia.
Blood flukes are known as schistosomes because of the "split body" on the ventral side of the male , in which the female is held during insemination and egg laying.
Man is the definite host harbouring adult parasites, and fresh water snails are intermediate hosts.
Source(s):
http://www.histopathology-india.net/Schisto.htm