The spread of the emerging pathogen Vibrio vulnificus biotype 2 serovar A in Danish anguilliculture is reported. Serovar A was originally isolated in a Spanish eel farm in 2000 and occurred in Denmark in the summer of 2004, affecting eels of 5-10 g body weight cultured in fresh water. The Danish eels showed clinical signs different from those reported for Spanish eels, such as severe haemorrhages in the head and gill region with necrosis of the soft tissues. Danish isolates were biochemically and serologically identical to Spanish serovar A strains and also highly virulent for eels by both intraperitoneal injection and immersion challenges. Vaccination with Vulnivaccine, a vaccine against V. vulnificus serovar E, cross-protected eels against serovar A. The LD(50) for experimentally infected vaccinated animals was significantly higher than for non-vaccinated animals.