الفهرس 
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Abstract
This study aimed to investigate about the effect of direct exposure of T. gondii cysts to
water of different degrees of salinity and resistance of cyst in these water for 24 hours,
any morphological change of the cyst was not observed, also occured reactivation of
tachyzoites in Vero cells from seawater and brackish water incubated cysts but In
contrast, any tachyzoites were not reactivated from fresh water incubated cysts,
Longer exposure of T. gondii cysts to brackish water showed survival of cysts in
brackish water at least for 6 days. So we can conclude that cyst can survive and remain
infective for at least 1 day in seawater, 6 days in brackish water and for 12 hours in
fresh water this when directly exposed and this indicate that the brackish water is the
most dangerous as cysts can survive in it for at least one week. Studying the uptake
and infectivity of T. gondii in hard clam (M.mercenaria) using in vitro cell culture,
PCR and mouse bioassay, results revaled that hard clam has very low ability to filtrate
and retain T. gondii cysts. Finally, more attention on oocysts is needed together with
studying the role of cysts and infected dead bodies as a considerable health threat.