title: A vaccination and challenge model using calcein marked fish.
abstract: A vaccination and challenge cohabitation model was established and evaluated using Nile tilapia (Oreochromis niloticus), the fluorescent chromophore calcein, and a Streptococcus iniae vaccine. Tilapia were non-invasively calcein marked, sham-vaccinated (CMSV) and cohabited with non-marked sham-vaccinated (NMSV) or non-marked S. iniae vaccinates (NMV) as a single unit. 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 period of 15 d. Calcein marking did not have a significant effect on S. iniae susceptibility as mortality of CMSV and NMSV was not significantly different (P=0.6756). Nor did calcein marking have an effect on the vaccination and challenge cohabitation model. The results showed that the cumulative mortality of CMSV (N=160) was significantly greater (P<0.0003) than those of NMV (N=160). The results of the calcein marking trials indicate that the most suitable calcein concentration and exposure time to produce detectable fluorescent marking of tilapia was 500 mg L(-1) for 4 h. 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. 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. The vaccination and challenge cohabitation model also offers the statistical advantage of using individual fish as the experimental unit maintained in the same aquarium.
authors: U.S. Department of Agriculture, Agricultural Research Service, Aquatic Animal Health Research Laboratory, Auburn, AL 36831-0952, USA. pklesius@ars.usda.gov
authors: Phillip H
authors: PH
authors: Klesius
authors: Joyce J
authors: JJ
authors: Evans
authors: Craig A
authors: CA
authors: Shoemaker
authors: David J
authors: DJ
authors: Pasnik
mesh_terms: D000818:Animals; D017756:Aquaculture / Q000379:methods; D001428:Bacterial Vaccines; D023681:Cichlids; D005393:Fish Diseases / Q000401:mortality / Q000517:prevention & control* / Q000635:transmission*; D005452:Fluoresceins / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000378:metabolism; D013290:Streptococcal Infections / Q000401:mortality / Q000517:prevention & control / Q000635:transmission / Q000662:veterinary*; D013291:Streptococcus
chemical_list: D001428:Bacterial Vaccines; D005452:Fluoresceins; D005456:Fluorescent Dyes; C007740:fluorexon