Growth of Atlantic salmon Salmo salar after intraperitoneal administration of vaccines containing adjuvants.

Growth of Atlantic salmon after intraperitoneal (i.p.) administration of adjuvanted vaccines was studied using groups of individually tagged fish held together in one tank or pen under commercial farming conditions. Parallel experiments were initiated at 2 freshwater sites and 1 marine site. Trivalent (vibriosis, cold water vibriosis and furunculosis) vaccines containing oil or beta-1, 3 glucan as adjuvants were used for immunisation of pre-smolts, whereas identical formulations containing furunculosis antigens only were used in growers. Control fish remained unvaccinated. No outbreak of bacterial or viral disease was experienced at any of the sites. At all sites, the highest daily growth rate was recorded in unvaccinated fish. At one site, the average weight of post-smolts that had received oil-adjuvant vaccine was significantly reduced by 345 g (23%) after 15 mo. Impaired growth rate was associated with increasing severity of intra-abdominal lesions as determined during necropsy. At the second post-smolt site and in growers, weight development and growth rates were non-significant between groups throughout the study. The results indicate that intraperitoneal administration of oil-adjuvanted vaccines may retard growth of farmed Atlantic salmon, although the extent of this effect may vary between sites. Unidentified factors coinciding with vaccination are thought to have caused the highly variable results seen between parallel sites in this study.