ARS | Publication request: Influence of tricaine methanesulfonate on Streptococcus agalactiae vaccination of Nile tilapia (Oreochromis niloticus L.)

Submitted to: Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 7, 2008
Publication Date: N/A

Interpretive Summary: Tricaine methanesulfonate (MS-222) is currently the only anesthetic approved by the United States Federal Drug Administration for use in foodfish. This anesthetic has been used to facilitate several manipulative processes, including handling, sorting, transport, diagnostic evaluation, and vaccination. Foodfish vaccination commonly involves the use of anesthetics to immobilize fish and limit stress responses, thus minimizing injury to the fish and hindering immunosuppressive stress responses that may affect vaccine efficacy. However, other authors have reported that anesthetic treatment itself can be a stressor and thus would have a negative impact on vaccination. Experiments were conducted to study the effect of MS-222 on blood glucose levels and percent cumulative survival of Nile tilapia (Oreochromis niloticus L.) challenged with Streptococcus agalactiae 30 d post-vaccination with S. agalactiae vaccine or sham-vaccination with tryptic soy broth (TSB). Anesthesia-treated fish were placed in an MS-222 solution to achieve stage 3, while control fish were placed in a sham anesthetic solution containing water but no MS-222 for an equal amount of time. All fish were then injected intraperitoneally with S. agalactiae vaccine or TSB. After 30 d post-vaccination, all fish were subsequently injected intraperitoneally with S. agalactiae without MS-222 treatment. Blood samples were taken throughout the experiments to measure blood glucose levels. Blood glucose levels among the groups immediately after anesthesia and sham anesthesia but prior to vaccination were significantly different. Blood glucose levels were not significantly different between the treated and control fish at any other time points following vaccination or challenge. Percent cumulative survival among challenged vaccinated fish was 50% when treated with MS-222 versus 100% when not treated with MS-222. However, percent cumulative survival among challenged non-vaccinated fish was 80% when treated with MS-222 versus 29% when not treated with MS-222. Increased blood glucose levels prior to vaccination were significantly correlated to decreased percent cumulative survival after challenge. Given the increase in blood glucose levels and significant decrease in percent cumulative survival among MS-222-treated, vaccinated fish, consideration should be given when anesthetizing Nile tilapia with MS-222 prior to vaccination.

Technical Abstract: Experiments were conducted to study the influence of tricaine methanesulfonate (MS-222) on blood glucose levels and percent cumulative survival of Nile tilapia (Oreochromis niloticus) challenged with Streptococcus agalactiae 30 days post-vaccination with S. agalactiae vaccine or sham-vaccination with tryptic soy broth (TSB). Anesthesia-treated fish were placed in an MS-222 (50 mg/L) solution to achieve stage 3 of anesthesia, while control fish were placed in a sham anesthetic solution containing water but no MS-222 for an equal amount of time. All fish were then injected intraperitoneally with S. agalactiae vaccine or TSB and later injected intraperitoneally with 750 cfu S. agalactiae/fish. Blood glucose levels among the groups immediately after anesthesia (92.8 ± 5.6 and 73.2 ± 4.2 mg/dL) or sham anesthesia (56.7 ± 2.6 and 58.9 ± 3.5 mg/dL) were significantly higher in the MS-222-treated groups (P < 0.0001). No other significant differences in blood glucose levels between treatment groups were observed at subsequent sampling points. Percent cumulative survival among challenged vaccinated fish was 50% when treated with MS-222 versus 100% when not treated with MS-222 (P < 0.0001). However, percent cumulative survival among challenged non-vaccinated fish was 80% when treated with MS-222 versus 29% when not treated with MS-222 (P < 0.0007). Increased blood glucose levels prior to vaccination were significantly correlated to decreased percent cumulative survival after challenge (r2 = 0.5364; P = 0.0022). Given increased blood glucose and decreased survival among MS-222-treated, vaccinated fish, consideration should be given when anesthetizing Nile tilapia with MS-222 prior to vaccination.