EUS was first detected in 1971 as Red Spot Disease and since then it is adversely affecting the fisheries economics. The conflicting views of various workers regarding the causative agent of EUS have created confusion rather than providing solution of the problem. It is observed that the scientists are working separately on different aspects of EUS and everybody is trying to prove the aspect of his study as the cause of the disease. The complicated nature of problem requires well-connected and co-operative efforts for this problem. Efforts have been made to develop systems of EUS through experimental infection trails since 1988 by various workers, based on which it has been considered of viral origin, bacterial origin and fungal origin. However, nobody could develop the symptoms exactly to that of the EUS. The symptoms produced have been pathogen specific. This book has written as compilation of methodologies for the diagnosis of any animal syndrome. It provides an experimental setup which shall be applicable to all such type of syndrome.