Human schistosomiasis, commonly called “bilharziasis” after a German pathologist, Theodor Bilharz (who first discovered the parasitic agent in Egypt in 1851) is caused by parasitic trematode of the genus, Schistosoma. There are at least 19 varieties of schistosomes, of which five are pathogenic parasites of man: S. haematobium, S. mansoni, S. japonicum, S. intercalatum and S. marteei (WHO, 1985). There are two types of human schistosomiasis in Nigeria: urinary schistosomiasis caused by infection of S. haematobium and intestinal schistosomiasis caused by the infection of S. mansoni. Different species of freshwater snail which breed in rivers, streams, lakes (both natural and man-made), ditches, paddy field, irrigation, canals etc are the intermediate hosts. The snail intermediate host of S. haematobium is Bulinus while the intermediate hosts of S. mansoni belong to the genus Biomphalaria. Human infection occurs when cercariae (that emerged from the nail intermediate hosts) penetrate the skin of man exposed to contaminated water. In man, the clinico-pathological damage caused by schistosomiasis is serious and is related to the reaction of the host tissues to the migrating young worms, the eggs laid by the adult worms, and the number of schistosomes eggs trapped in the tissues. Details of these have been presented by Odeku et al (1968). Makenna et al (1997), Elem (1998), Udonsi (1999), Anosike et al (2002). Bio-Research Vol.2(1) 2004: 103-114
EB Nwoke, INS Dozie, EA Nwoke, JC Anosike
