EVALUATION OF CROSS-PROTECTION BY VACCINES AGAINST ATYPICAL AND TYPICAL FURUNCULOSIS IN ATLANTIC SALMON, SALMO-SALAR L

In Iceland, farmed salmonids are vaccinated against A. salmonicida ssp . achromogenes (Asa), which causes atypical furunculosis and is endemi c in local waters. Classical furunculosis, caused by A. salmonicida ss p. salmonicida (Ass), was not diagnosed in this country until June 199 5. In the present study, protection in experimental challenges against atypical and classical furunculosis in Atlantic salmon vaccinated wit h an autogenous Asa bacterin (Iceland Biojec. OO, IBOO), a commercial furunculosis vaccine (Biojec. 1500), or a mixture of both vaccines was compared. The results showed that both vaccines gave protection again st an injection challenge with Asa. However, better protection was obt ained with the IBOO (homologous) vaccine. Infection of Asa by cohabita tion could not be established in fresh water. Fish vaccinated with Bio jec. 1500 or with both vaccines simultaneously were equally well prote cted against Ass in a cohabitation challenge. On the other hand, no pr otection against classical furunculosis was achieved in fish vaccinate d by IBOO alone.