Abstract
The tissue location of Vibrio anguillarum bacterin in rainbow trout was studied using three delivery methods : intraperitoneal (IP) injection, immersion and per os. The fate of the bacterin was determined using histologically sectioned trout stained with anti-V. anguillarum (strain LS-174) fluorescein-labeled, purified, rabbit immunoglobulin G (IgG). The bacterin administered IP was accumulated by macrophages and observed in the kidney and spleen 28 d after injection. Bacterin delivered by immersion was observed on the surface of the gills, and in the gastrointestinal tract and kidney. Vaccine administered by the oral route was not detected systemically in test fish; the only accumulations found were in the lamina epithelialis of the lower intestine. Immunity developed with bacterins administered either by IP injection or immersion was considered to be systemic, because after vaccination, antigen was observed in a variety of internal fish tissues. Oral immunization apparently caused induction of a mucosal response because no antigen was observed in organs other than the intestine.
