TWENTY-THIRD ANNUAL EASTERN FISH HEALTH WORKSHOP JOHN CARVER INN, PLYMOUTH, MA 30 MARCH - 2 APRIL, 1998 Vaccination Against Furunculosis: Is Our Faith Justified? Maura Hiney Fish Disease Group, Department of Microbiology, National University of Ireland - Galway, Galway City, Republic of Ireland Over the last 15 years, furunculosis has been one of the major bacterial diseases affecting salmonids in both the Irish commercial and public fisheries sectors. This disease has caused losses to 40% in one year within individual farms. With the application of vaccine technology to disease control in fish species and the development of oil-adjuvant Aeromonas salmonicida vaccines, furunculosis is no longer perceived as a problem in the commercial sector in Ireland and elsewhere in Europe. The decline in the incidence of furunculosis in commercial aquaculture would certainly suggest that vaccination has been a successful management strategy. However, outbreaks of furunculosis continue to occur and, in the past few years, an increase has been observed in the incidence of furunculosis in freshwater commercial hatcheries, even following vaccination. This paper examines available evidence on the real, rather than the perceived impacts of oil-based vaccination. First, data on the incidence of furunculosis, both in Ireland and in a number of other European countries, while incomplete, would suggest that events which led to a European-wide decline in furunculosis during the early 1990's was not a direct consequence of the introduction of widespread oil-based vaccination. This data indicates that vaccination cannot be considered a foolproof prophylactic treatment against the occurrence of clinical furunculosis. Secondly, work carried out in Galway has demonstrated that vaccination will not protect fish, covertly infected with A. salmonicida, from developing clinical furunculosis following both artificial and natural stresses. Thus, it is argued that vaccination cannot be thought of as a barrier to the spread of furunculosis following movement of salmonids from one freshwater site to another. This raises a number of questions about the efficacy and robustness of furunculosis vaccines, the possibility of creating immune carriers, and the impact of restocking covertly infected vaccinated fish stocks on resident populations.   Return to 23rd Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page