EXPERIMENTAL-INFECTION WITH VIBRIO-SALMONICIDA IN ATLANTIC SALMON (SALMO-SALAR L.) - AN EVALUATION OF 3 DIFFERENT CHALLENGE METHODS

In testing the efficacy of vaccines for cold water vibriosis in Atlant ic salmon a reliable challenge method is essential. Three different ch allenge methods with Vibrio salmonicida in Atlantic salmon (Salmo sala r L.) were evaluated. The results from 20 batch release tests for vacc ines against cold water vibriosis in a test system using intraperitone al (i.p.) injection were evaluated with respect to the EU guidelines f or vaccines intended for fish. Nine bath challenges employed in the de velopment of new vaccine candidates, and one pilot study using a cohab itation challenge, were also included. Review of the test results show ed that the i.p. injection was the most reliable method of inducing co ld water vibriosis with cumulative specific mortalities in controls ab ove 70% during a three-week observation period post challenge. Ninetee n out of 20 challenges fulfilled this criterium. For the bath challeng es, only six out of nine challenges succeeded in reaching the same lev el. In the single pilot study using cohabitation challenge, the diseas e was transferred from cohabitants to the test fish, but cumulative sp ecific mortalities did not reach the minimum levels stated in the EU g uidelines. (C) 1997 Elsevier Science B.V.