Vaccines for Tilapia in Aquaculture

Since the advent of large-scale commercial tilapia farming, a lot of efforts have gone into the development of a vaccine that will prevent streptococcosis in tilapia. Vaccines are not only helpful for the individual fish; they can also decrease the amount of bacteria in each population since the number of possible host goes down. This means that even unvaccinated individuals benefit from the vaccine, since their risk of encountering an infected host is decreased. This protective effect is called herd immunity. Even if a vaccine fails to reach 100% of a population, it can still decrease the risk of disease outbreaks in non-vaccinated fish as long as the percentage of vaccinated fish is large enough. It is difficult for infectious disease to spread in a population where a major part of the animals are immune.