An ulcerative skin disease which is very similar clinically to that reported in Japanese eel (A. japonica) has caused morbidity in both wild and captive populations of American eel (Anguilla rostrata) in North Carolina, USA. Lesions appear to begin as localized, depigmented foci which spread to form large patches of necrotic skin up to 1600 mm2 in area. The depigmented patches detach at the dermo-epidermal junction, forming large ulcers that expose underlying muscle. The infection commonly affects the head, producing cranial swelling and corneal edema.

A mild to severe, primarily mononuclear infiltrate is seen, most prominently in large ulcers. Many lesions had extensive collagen deposition, which contributed to the tissue swelling. Culture of skin lesions in various stages of development revealed the consistent presence of bacterial isolates that were biochemically and immunologically identified as Aeromonas salmonicida. This agent was the predominant organism by colony type in 17 of 20 skin cultures and usually appeared to constitute over 90% of the colonies present. Kidney samples were free of infection.