Photobacterium Damsela infections have been confirmed in the USA, Japan, Taiwan, Spain, Greece, France, Portugal and Norway. Though previously confused with the other common fish pathogens, Vibrio anguillarum and Aeromonas salmonicida subsp. Salmonicida, this bacteria differs from the others as well as Pasteurella spp. Researchers have found that isolates from several European countries, Japan and the USA are biochemically and antigenically similar, with homogeneous lipopolysaccharide (LPS) electrophoretic patterns and membrane protein profiles.

The disease is usually diagnosed at water temperatures above 20-22°C but the pathogen can be isolated from clinical cases with low chronic mortalities in nurseries even at a water temperature of 15°C. Therefore, Pasteurellosis is a "summer window" disease in the cage farms while it can be diagnosed throughout the year in hatcheries especially if broodstock fish are carriers or when water input is not UV or ozone treated.

Disease reprinted courtesy of OIE Diagnostic Manual for Aquatic Animal Diseases, OIE (World Organisation for Animal Health), Paris, France.