Vaccination against yersiniosis

Yersiniosis is a disease caused by Yersinia ruckeri, which mostly affects salmonids during their hatchery stage. Vaccines against yersiniosis have been commercially available for more than 40 years. These vaccines are inactivated bacterins, and are mostly applied by immersion. Boosters are often required to ensure longevity of protection. Since the late 1980s, biotype 2 variants of Y. ruckeri started to cause infections and are now the major variants causing yersiniosis throughout the US and Europe. This emergence of new variants resulted in the changes in the biotypes used for vaccine production.