When Dr Stanisław Snieszko and colleagues injected carp with the first fish vaccine in the late 1930s, they declared that although effective, immunisation was “too complicated and time consuming for large scale application in fish farms”. Jump forward to today, and vaccines are available for 17 different kinds of fish species, protecting them against 22 different bacterial and 6 different viral diseases. Developing fish vaccines is challenging, but as Dr Maryam Dadar (Razi Vaccine and Serum Research Institute in Iran) and colleagues highlight in a paper recently published in ‘Reviews in Fisheries Science & Aquaculture’, significant progress is being made.
Vaccines typically come in one of two different flavours – inactivated vaccines and attenuated vaccines. Both involve giving the fish a dose of the pathogen we want to protect the fish against, but inactive vaccines use dead pathogens whilst attenuated vaccines use live pathogens, albeit in a weakened form so they don’t actually cause illness. Attenuated vaccines can provide better immunity than inactivated vaccines, and can also be used to treat young fish (by immersion). However since they use a live pathogen, there is a small risk that some residual virulence may remain and the treated animal – or those that come in contact with the animal, could become infected...
This article was written for (and can be read in full at) The Fish Site.