International Journal of Scientific & Engineering Research Volume 10, Issue 1, January-2019 610 ISSN 2229-5518 IJSER © 2019 http://www.ijser.org Effects of Heavy Metals and Pathogenic Bacteria on the Antioxidant Enzyme Activities and Immune Response of Clarias gariepinus in Egypt Mohamed H. Bahnasawy 1 , Entsar A. Saad 2 , Hasan A. Maroof 3 , Samah A. Abou Shehatta 2,3,* 1 Zoology Department, Faculty of Science, Damietta University, Egypt 2 Chemistry Department, Faculty of Science, Damietta University, Egypt 3 Food Inspection Laboratory, Damietta Port, Animal Health Research Institute, Giza, Egypt Abstract—The aim of this study was to measure chemical, bacteriological, and biochemical changes of fish to determine the pollutants level and their effects on Clarias gariepinus (catfish) quality. The study was applied on samples at Shatta (site1) and Lake El-Burullus (site 2). The obtained results revealed that (site1) had greater concentrations of heavy metals. Moreover, the antioxidant parameters revealed noticed increase in MDA in fish samples from both sites, reduced levels of SOD, catalase, glutathione reductase and TAO in fish samples from (site1). These results showed that antioxidant enzymes can be used as biomarkers of heavy metals pollution. Index Terms— Antioxidant parameters, biochemical changes, Clarias gariepinus, heavy metals, pollution, pathogenic bacteria ——————————  —————————— 1 INTRODUCTION orld consumption of fish has increased simultaneously with the growing concern of their nutritional and therapeutic ben- efits. In addition to its important source of protein, fish have rich contents of essential minerals, unsaturated fatty acids and vit- amins [1]. Water contamination has been long reported as the major threat to the aquatic environment [2].When fish are exposed to these metals in an aquatic ecosystem, they tend to take these metals up which may accumulate in various tissues in significant amounts and are eliciting toxicological effects at critical targets [3]. Increase in agricultural pollution and industrial growth, with consequent impacts on aquatic ecosystems are a major focus of research worldwide [4]. Many pollutants mediate their toxicity through oxidative stress, resulting in changes in antioxidant defenses as well as damage to proteins, membrane lipids and DNA molecules, the result of such exposure leading to oxidative stress can impair cellular or biologi- cal function which lead to disease [5]. Fish are suitable candidates for the study of oxidative stress induced by pollutants [6]. Oxida- tive stress can lead to oxidative damage in cellular molecules [7]. Heavy metal pollution increase the susceptibility of aquatic ani- mals to various diseases by interfering with the normal functioning of their immune, reproductive, and developmental processes [3]. Pollution with heavy metals influence the immune system of fish, leading to impairment of their health or even increase their mortali- ty [8]. Total volatile base, taken as an indication for bacterial growth, while the ammonia comes from decomposition of amino acids, thus reducing the quality of the available protein [9]. Salmonella is a common food borne pathogen, causing major health problems [10]. Municipal sewage, agriculture pollution, and storm water runoff are the main sources of these pathogens in waters [11]. Esche- richia coli is the best thermo-tolerant pollution indicator [13]. It is estimated that 2–7% of E. coli infections result in acute renal fail- ure [11]. L. monocytogenes is a concern to public health because of its abil- ity to survive under harsh conditions. Therefore, it is considered a serious public health risk. It spreads through the consumption of food products and its related-disease can be fatal to humans and animals [12]. The discharge of untreated sewage into seawater was involved in contamination of fish with L. monocytogenes [13]. Heavy metals are considered major pollutants of aquatic envi- ronments due to the difficulty of metabolization and the bioaccu- mulative potential in tissues of aquatic organisms [14]. Heavy met- als including mercury, lead, and cadmium alter host's immune sys- tem and lead to increased susceptibility to infections and autoim- mune diseases [15]. Cancer caused by Pb is a potential issue [16]. Cadmium is an extremely toxic heavy metal, result in alterations of the physiological processes in the blood and tissue of fish [17]. Hg is extremely toxic to animals and human health through var- ious absorption pathways [18], it induced oxidative stress on ex- posed fish, since inhibition of antioxidant enzymes activity, in- creases in lipid peroxidation, DNA damage, and micronuclei fre- quency occurred [19]. Recently, it has the ability to bind to a variety of biomolecules, which can compromise its structure and function- ality and thus promote its toxic effects [20]. 2 MATERIALS AND METHODS 2.1 Study Area The study was conducted on two areas, the first one is Shatta vil- lage, located in Damietta Governorate, is characterized by many aquaculture fish farms. The main growing water supply is an ex- tension of the water of Lake Manzala, which lies between some Governorates in Eastern Delta, Egypt. It is exposed to constant pol- lution from different sources, notably the most dangerous one is the untreated domestic human sewage waste, in addition to agricultur- al and industrial pollution including the presence of garbage recy- cling factory neighboring this area leading to smoke spreads as a result of garbage burning. The second area is Lake El-Burullus. It is an important lake, large, shallow, and fresh to brackish salt-water lagoon, located on the coastal bulge of the North Central Delta region between the W IJSER