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Abstract
Schistosomiasis is a series of diseases in man that is caused by some species of the genus Schistosoma. It is one of the most significant public health problems in Egypt. Many efforts have been done to decrease its incidence in the last few years.
Schistosomiasis was present in Egyptian mummies since ancient times. In Egypt there are two species of the genus Schistosoma which are Schistosoma mansoni and Schistosoma haematobium. Environmental changes that resulted from the development of water resources and the growth and migration of populations are responsible for the introduction of the disease into new geographic areas.
In Egypt the planorbid fresh water snail Biomphalaria alexandrina serves as the intermediate host for S.mansoni. Biomphalaria glabrata is the intermediate host of S. mansoni in Carebian. Its presence was first reported in Egypt in 1982. Other studies between the years 1996 and 2004 confirmed this presence, together with a hybrid between this snail and the indigenous B.alexandrina in some areas of Egypt. However, this was denied by other works utilized molecular analysis.
Biomphalaria glabrata is a large snail and its presence in Egyptian water courses is of epidemiologic importance.
The relationship between the snail host and the parasite is influenced by environmental, parasite and snail factors. Snail factors are the age, genetics and immunity of the snail.
During intermolluscan development of the parasite, several complex processes take place resulting finally in escape of the cercariae in susceptible snails, or arrest of normal development of the penetrating miracidium mostly at the sporocyst stage and failure of shedding in resistant snails. This process is controlled by genetic factors.