Abstract
Currently, there is a growing demand to determine the protective status of vaccinated fish in order to prevent diseases outbreaks. A set of different parameters that include the infectious and immunological status of vaccinated salmonids from 622 Chilean farms were analyzed during 2011–2014. The aim of this study was to optimize the vaccination program of these centers through the determination of the protective state of vaccinated fish using oral immunizations. This state was determined from the association of the concentration of the immunoglobulin M (IgM) in the serum and the mortality rate of vaccinated fish. Salmonids were vaccinated with different commercial mono- or polyvalent vaccines against salmonid rickettsial septicemia (SRS) and infectious salmon anemia (ISA), first by the intraperitoneal injection of oil-adjuvanted antigens and then by the stimulation of mucosal immunity using oral vaccines as a booster vaccination. The results showed that high levels of specific IgM antibodies were observed after injectable vaccination, reaching a maximum concentration at 600–800 degree-days. Similar levels of antibodies were observed when oral immunizations were administrated. The high concentration of antibodies [above 2750 ng/mL for ISA virus (ISAv) and 3500 ng/mL for SRS] was maintained for a period of 800 degree-days after each vaccination procedure. In this regard, oral immunizations maintained a long-term high concentration of anti-SRS and anti-ISAv specific IgM antibodies. When the concentration of antibodies decreased below 2000 pg/mL, a window of susceptibility to SRS infection was observed in the farm, suggesting a close association between antibody levels and fish protective status. These results demonstrated that, in the field, several oral immunizations are essential to uphold a high level of specific anti-pathogens antibodies and, therefore, the protective status during the whole productive cycle.
Highlights
The Salmon industry has significantly increased worldwide over the last two decades
Detection of P. salmonis and ISA virus (ISAv) Specific immunoglobulin M (IgM) Antibodies on Vaccinated Fish When the sera collected from fish at the different aquaculture farms were analyzed to detect anti-P. salmonis and anti-ISAv antibodies, the results showed that specific IgM antibodies against both pathogens increased significantly after vaccination
There is a growing demand to establish the protective status of fish and determine how this correlates with immunological signatures after vaccination to provide evidence of the efficacy and the protective state conferred by vaccines [11]
Summary
The Salmon industry has significantly increased worldwide over the last two decades. In Chile, the industry has rapidly grown becoming one of the most important factors in the country’sOral immunizations protect salmonids development. Piscirickettsia salmonis and ISA virus (ISAv) provoke salmonid rickettsial septicemia (SRS) and infectious salmon anemia (ISA), respectively, and have caused severe outbreaks during the last 6 years in Chile, resulting in significant loss of salmon production. Vaccination against these pathogens in farmed salmonids is mostly administered using an inactivated bacteria or virus emulsified in an oil-adjuvanted preparation given via an intraperitoneal (i.p) injection. We have demonstrated that mucosal stimulation by oral vaccination against SRS is less stressful for fish, delivers strong protection and is very safety [1] This vaccination method is advantageous for both small-sized salmon and large-scale procedures, making it ideal for successive long-term immunizations during the sea-water growth stage. One of the main problems to do this is the absence of information to indicate changes in the protection status of salmonids during the course of their production cycle
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