Investigation and Identification of the Most Bacterial Infection in the Invasive Nile Tilapia Fishes in Euphrates River Banks, Al-Najaf Province, Iraq

This study was conducted to identify and diagnose the major bacterial pathogens affecting the Nile tilapia (Oreochromis niloticus L.) collected from the banks of the Euphrates River in Al-Najaf Province. A total of forty live Nile tilapia showing disease symptoms were sampled between November and December 2024. Samples were collected from the skin, gills, and internal organs, including the liver, spleen, kidney, and gastrointestinal tract (GIT). The samples were cultured on different media, and the results revealed the presence of Escherichia coli, Aeromonas spp., Staphylococcus aureus, and Salmonella spp. Pathological changes observed in the affected fish included necrotic and skin ulcers, widespread hemorrhagic spots, exophthalmia (eye protrusion), visceral congestion, and pale liver coloration. The findings confirmed that members of the Enterobacteriaceae family are the most prevalent bacteria in the Nile tilapia. Moreover, Salmonella spp. were found to be passively carried by fish and are capable of causing a wide range of diseases, including bacteremia and gastroenteritis. In addition, the study demonstrated that E. coli is associated with serious health disorders in the Nile tilapia. Importantly, the consumption of diseased fish poses significant risks to public health, including food deterioration, food poisoning, and food intoxication.