A. salmonicida is a Gram-negative, non-motile, rod-shaped and facultative anaerobic bacterium, that is the causative agent of furunculosis in both salmonids and non-salmonids species. This systemic fish disease is characterized by high mortality and morbidity and is a significant cause of economic losses in the aquaculture of trout and salmon. Atypical strains produce ulcer disease and erythrodermatitis that can lead to high mortality. Aeromonas salmonicida is a pathogenic bacterium that severely impacts salmonid populations and other species. It was first discovered in a Bavarian brown trout hatchery by Emmerich and Weibel in 1894. Aeromonas salmonicida's ability to infect a variety of host, multiply, and adapt, make it a prime virulent bacterium. salmonicida is an etiological agent for furunculosis; a disease that causes septicemia, haemorrhages, muscle lesions, inflammation of the lower intestine, spleen enlargement, and death in freshwater fish populations. It is geographically found worldwide with the exception of South America. The major route of contamination is due to poor water quality; however, it can also be associated stress factors such as overcrowded areas, high temperatures, and trauma. Spawning and smolting fish are prime victims of Furunculosis due to their immuno-compromised state of being.