Abstract
Stress-induced epidemic parasites and bacterial diseases are becoming a typical occurrence in fish aquaculture across the globe, those consider deadly infectious pathogens. To prevent losses on fish farms, it is crucial to obtain information on the infection severity and the characteristics of those diseases which have been peaked for fish farms and lead to mass mortality. This study investigates the effect of dual parasitic and bacterial infection on farmed tilapia, which leads to losses in farmed fish; focuses on the harmful effect of polluted water on speared infections in farming. During the production season, water and fish specimens were taken from private fish farms in El-Sharkia and Kafr El-Sheikh, Egypt, particularly during significant mortality times. The infected and uninfected fish samples were examined to determine bacteriological, parasitological, haemato-biochemical indices, immune responses, and pathologic changes besides water analysis in fish farming in the study area. It was discovered that fish were significantly infected with Centrocestus formosanus encysted metacercariae and/or Cichlidogyrus tilapiae, Heterophyes spp. Also, three species of gram-negative: Aeromonas hydrophila, A. sobria, Pseudomonas aeruginosa, and two Gram-positive cocci: Streptococcus agalactiae and Enterococcus faecalis. Identification of bacterial isolates was confirmed by using 16S rRNA gene sequencing. Results demonstrated substantial (P < 0.05) output losses in both farms. Results displayed negative effects of dual infection on the lost weight, whole-body biochemical, haemato-biochemical indices, digestive enzyme, immune responses, gene expression, and abnormal features histopathology in different organs of infected Nile tilapia. At the same time, most of the water Indices strayed considerably from standards. Thus, the obtained data indicated the detrimental impacts of dual infection and water quality deterioration on the health condition of Nile tilapia and might help us acquire a deeper understanding of yield loss as potentially severe economic repercussions for fish farms.