Experimental vaccination of Atlantic salmon (Salmo salar L.) against marine flexibacteriosis

Tenacibaculum maritimum infections can cause losses in mariculture, however there is no commercially available vaccine in Australia. A vaccination trial was undertaken using 4 groups: Control, IP Control, Vaccine, and Vaccine + Adjuvant. Within the challenge period of 27 days, significant protection was demonstrated in fish injected with the Vaccine + Adjuvant compared to all other groups. RPS values were calculated at 79.6% and 78.0%. Fish vaccinated without adjuvant did show lower mortalities than unvaccinated fish, however, it was not significantly different from both unvaccinated groups. Low RPS values at 27.7% and 22.0% indicate that the vaccine without adjuvant could not provide sufficient protection from a moderate challenge of T. maritimum. Side effects of the oil based adjuvant, Freund's incomplete adjuvant (FIA) were noted. All fish injected with the Vaccine + Adjuvant had black/brown pigment associated with the external surface of the fundic region of the stomach. Histological examination revealed this material to be black/brown pigmentation most likely caused by melanin. An inflammatory response was noted around this material with the formations of granulomas and cysts.