Submitted to: Fish and Shellfish Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2005
Publication Date: 1/1/2006
Citation: Klesius, P.H., Evans, J.J., Shoemaker, C.A., Pasnik, D.J. 2006. A vaccination and challenge model using calcein marked fish. Fish and Shellfish Immunology 20 issue 1: 20-28. Interpretive Summary: The development and evaluation of fish vaccines is dependent on a reliable pathogen challenge model. Cohabitation pathogen challenge is regarded as one of the best model for evaluation of fish vaccine potency that most mimics natural conditions. In order to develop and evaluate a cohabitation and pathogen challenge model, our first objective was to evaluate calcein marking and detection to distinguish between control and vaccinated fish. We demonstrated that control fish can be successful marked with fluorescent chromophore calcain and cohabited with vaccinated fish as a single unit (tank). Furthermore, the calcein marks are readily visible in the calcified skeletal structures of head and fish using a handheld UV lamp. We believe that this model will be useful to compare different vaccine lots, competitive vaccines and vaccine efficacy under varied conditions. The cohabitation vaccination and pathogen challenge model also offers the statistical advantage of using individual fish as the experimental unit maintained in the same aquarium.
Technical Abstract: A cohabitation vaccination and challenge model was established and evaluated using Nile tilapia (Oreochromis niloticus) and a Streptococcus iniae vaccine. Sham-vaccinated fish were non-invasively marked with the fluorescent chromophore calcein and cohabited with the S. iniae vaccinated fish as a single unit (tank). After 30 d the cohabitants were challenged with a virulent isolate of S. iniae by intraperitoneal (ip) injection and the cumulative mortality was measured over a protection period of 15 d. The cohabitation model showed that the cumulative mortality of sham-vaccinates (N = 160) was significantly greater (P < 0.0001) then those of S. iniae vaccinates (N = 160). Furthermore, no significant effect was noted for tank (N = 8, P = 0.407), tank versus treatment (N = 2, P = 0.754), challenge dosage (N = 4, P = 0.214), or calcein-marking (N = 2, P = 0.520). Calcein appears to be a valuable tool for non-invasive, non-lethal, non-stressful, mass marking of fish to differentiate between sham- and pathogen-vaccinated fish in this cohabitation model. Furthermore, the calcein marks were readily visible in the calcified skeletal structures of head and fins using a portable handheld UV lamp set at 365 nm wavelength. The cohabitation vaccination and challenge model also offers the statistical advantage of using individual fish as the experimental unit maintained in the same aquarium.