الفهرس 
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Abstract
Summary
In the recent years much attention had been paid to water pollution specially cadmium which considered the majority of pollution of industry excreation.
The aim of this study is to explain the relation ship between cadmium pollution and internal parasitic infestation in tilapia fish.
The present study was carried out on 400 specimens of Tilapia fishes ( Oreochromis niloticus (O.niloticus) of different size and body weight. They were randomly collected from Kafr El- Sheikh governorate cultured fish farms. The collected fishes were obtained in autumn season 2010.
The results could be summarized as following :
The clinical signs of most examined fishes revealed no pathognomonic abnormalities on the external body surface except heavily naturally infested Tilapia fishes, represented as asphyxia, some aggregated on the surface, accumulated at the water inlet of the pond and air pump of aquaria. Others appeared dull with loss of escape reflex. Also, fishes were shown emaciation and exhausted with rapid respiration accompanied with sluggish movement, excessive amounts of mucus (slimness) covering the external body surface as well as scale sloughing.
The postmortem findings of investigated fish revealed the presence of haemorrhagic small wounds, black spots were observed in different parts of the body in some infested fishes. There were frayed ragged fins with darkening in colour of some fishes. While, internal organs appeared anemic with enlargement and congestion. As well, haemorrhage and ulceration of intestine and stomach mucous membrane. White nodules in posterior kidney.
The isolated parasites from examined tilapias were 6 species namely:
• Monogenetic trematodes Enterogyrus cichlidarum.
• Adult flukes including Orientocreadium batrochoides.
• Encysted metacercariae including Heterophidae .
• Cestodes including Polyonchobothrium sp.
• Nematodes including Procamallanas cyathopharynx.
• Acanthocephalan including Acanthocentis tilapiae.
Different spp. were recorded and discussed.
Helminthes infestations of O. niloticus in Sidi Salem district fish farms, trematodes were 11 %, nematode was 8 %, cestode was 1 % , Acanthocentis tilapiae were 4 % in autumn season. Also, Helminthes infestations of O. niloticus in Alirad district fish farms , trematodes were 9 % , nematode were 4 %, cestode were 1 % , Acanthocentis tilapiae were 2 % in autumn season.While, Helminthes infestations of O.niloticus in Meutobeus fish farms, trematodes were 6 % , nematode were 3 %, cestode were 1 % , Acanthocentis tilapiae were 2 % in autumn season.
The residues of cadmium in water and O. niloticus tissues naturally exposed to cadmium were determined and discussed the correlation between O. niloticus tissues naturally exposed to cadmium and internal parasitic infestation.
The histopathological examination in different organs of O. niloticus tissues naturally exposed to cadmium.