Vibrio anguillarum is a Gram-negative, curved-rod bacterium with one polar flagellum. It is an important pathogen of cultured salmonid fish, and causes the disease known as vibriosis or red pest of eels. The disease has been observed in salmon, bream, eel, mullet, catfish, and tilapia, amongst others. The organism is most prevalent in late summer in salt or brackish water and transmission is mainly horizontal by direct contact. It is widely distributed across the world.