Efficacy

The efficacy and protective ability of Norvax® Strep Si has been extensively tested in Asian seabass in various laboratory experiments and field trials. The duration of protection was proven to be at least 12 weeks in laboratory studies and 35 weeks in field trials.

Efficacy of immersion vaccination

The efficacy of immunity following immersion vaccination of Asian seabass with the recommended dose of Norvax® Strep Si was investigated by means of challenge experiments. A total of 50 5-g fish were vaccinated with Norvax® Strep Si while untreated contemporary fish were used as controls.

Three weeks after vaccination, the fish were challenged in a bath immersion using a virulent strain of Streptococcus iniae. Statistically significant higher survival was obtained in vaccinated fish (75%) compared with controls (22.5%). The relative percent survival (RPS)* was 68%.

Efficacy of injection vaccination

A field trial was conducted with Asian seabass under normal farming conditions. Fish (40 g) were injection vaccinated with the recommended dose of Norvax® Strep Si. The efficacy following injection vaccination was investigated by means of a challenge experiment. Six weeks after vaccination, 80 fish were challenged by intraperitoneal injection using a virulent strain of Streptococcus iniae. Statistically significant higher survival was obtained in vaccinated fish (100%) compared with controls (37.5%). The RPS was 100%.