freshwater intermediate host snail prevailing in
developing countries and have been recognized as the
intermediate host for Schitosoma mansoni, which is
responsible for wide spread schistosomiasis infections
in humans. B. alexandrina snails play an increasingly
important role in transmission of S. mansoni in Egypt and
they are considered to be potential hosts of the
schistosome parasite [1].
Molluscan innate immunity comprises humoral and elimination by oxidation of nonself particles.This process is accomplished by phagocytic haemocytes within the
blood and haemolymph of both vertebrate and
invertebrate animals [9]. Snail haemocytes are able to
mount a cytotoxic response against parasites [10] and are
apparently involved in the destruction of the sporocysts
of S. mansoni [11]. Many workers studied haemocytes as
molluscan internal defence or immune system [12 -15].
Some biochemical studies on the organic
composition of the haemolymph of some snails had
been carried out by Mobarez [16] and Moura et al.[17].
Also, plasma protein fractions were studied in a variety of
freshwater and marine species by employing a number of
methods of electrophoresis [18].
The digestive gland of mollusks is involved in
extracellular and intracellular digestion of food material,
absorption of nutrients, storage of lipids, glycogen and
minerals and it plays also a major role in detoxification
[19]. The snail’s digestive gland (hepatopancreas) was
described by Brackenbury [20].
The present work investigated the histological
alterations in the digestive glands of Biomphalaria
alexandrina infected snails. Also, the changes in hemocytes of B. alexandrina in infected snails were followed up using light and scanning electron microscopy to evaluate the capability of the snail to respond to parasitic infections