CAT and Splenomegaly: Similarly, both freshwater fish O. niloticus and Clarias gariepinus naturally infected with E. tarda had skin ulcers and hemorrhages, ascites, muscular hemorrhage, congested liver with splenomegaly; these signs were similar to those observed with the experimentally infected fish [53], in addition, Rao et al. [54] and Leung et al. [55] claimed that E. tarda produced bacterial toxins (various virulence factors) such as hemolysin, catalase and extracellular products (ECPs) that could attack the host cells causing tissue inflammation and damage resulting in immunodepression status in fish.