Edwardsiella tarda (E. tarda) was first isolated from infected humans and animals (Ewing et al. 1965). The bacterium is a common ubiquitous pathogen, and wide variety of animals act as reservoirs of bacteria as well as it is a part of the normal gut microbiota of aquatic animals. E. tarda can be spread to vulnerable fish via skin or gill damage when contacted with contaminated water source (faeces, water or mud). Globally, E. piscicida/tarda is an important fish pathogen affecting wide range of fish species (Leung et al., 2019). In addition, it induces disease in other animals such as marine mammals, pigs, turtles, alligators, ostriches, skunks, snakes, and humans. 

In Egypt, E. tarda was recorded in different freshwater fishes such as Nile tilapia, Oreochromius niloticus and common carp, Cyprinus carpio, African catfish, Clarias gariepinus (Noor El Deen et al., 2017; Algammal et al., 2022). Co-infection with Edwardsiella tarda and Edwardsiella anguillarum were also identified from Nile tilapia summer mortality syndrome (Elgendy et al., 2022).