Oral vaccination worked as well as injections against tilapia pathogen

Oral vaccination of Nile tilapia was found to be just as effective as an injectable vaccine in a study by scientists in Thailand, the Global Seafood Alliance reports in its Responsible Seafood Advocate online news site.

The study evaluated the efficacy of different routes of formalin-killed vaccine administration on immunity and disease resistance of Nile tilapia challenged with the pathogen Streptococcus agalactiae.

Vaccines can be administered in different ways, but the most common is by immersion, orally as a feed additive and direct injection. The method of administration depends on fish size and stage of development as well as the nature of the pathogen being vaccinated against.

Simplicity vs efficacy

Historically, vaccines have been administered via injection, but this is time-consuming and difficult to deliver to young fish. Oral and immersion vaccines are simple to administer with minimum stress to the fish, but often result in limited immune responses.

Results of the study led by researchers from Chiang Mai University confirm that vaccination with formalin-killed S. agalactiae significantly improved the resistance of Nile tilapia (Oreochromis niloticus) to infection and that the efficacy of oral administration of the vaccine was comparable to that of vaccine administered via injection, indicating that oral vaccination is a viable cost-effective alternative to administering vaccines by injection.

Tilapia is the world’s second most farmed finfish genus after carps, with more than 4.4 million tonnes (live weight) produced in 2020, comprising 9% of the 49.12 million tonnes of finfish produced in inland aquaculture that year.

Eliminate injection stress

“Based on our results, we suggest that the oral vaccination of Nile tilapia with formalin-killed S. agalactiae stimulated the serum and skin mucus immunity and is just as effective as an injectable vaccine,” concluded the authors of the study.

“By using this kind of vaccine, farmers can save time, cut down on the demand for highly skilled labour and eliminate the stress and attendant mortality associated with direct injection. However, we recommend a larger sample size, more replicates, and an analysis of a wider range of target genes as the focus of further studies.”

Read the full study, Efficacy of Different Routes of Formalin-Killed Vaccine Administration on Immunity and Disease Resistance of Nile Tilapia (Oreochromis niloticus) Challenged with Streptococcus agalactiae, published in the journal Fishes, here.