Protection conferred by the combined use of a mixture of two attenuated Salmonella Enteritidis and Salmonella Typhimurium vaccines against a double infection with both serovars

Salmonella spp. is the second most prevalent zoonotic pathogen in the European Union, and strictly related to poultry production, responsible for 60,050 human gastrointestinal infections during 2021. In terms of the most significant serovars, Salmonella Enteritidis and Salmonella Typhimurium accounted for approximately 54.6% and 11.4% of the reported cases, respectively. However, salmonelosis can be efficiently prevented by a One Health approach which considers the full farm-to-fork chain.

For that reason, control measures must be maintained constantly and cannot be reduced throughout the poultry production system, within vaccination highlights. Vaccination is a simple, safe, and effective way of protecting animals against diseases. In case of Salmonella control, the objective of vaccination is to prevent the colonization and reduce the spread of the pathogen since the beginning of the production cycle, when chicks are more susceptible to Salmonella infection. The combination of two vaccines against the predominant serovars is a valuable strategy to reduce farm operations, as both vaccines could be applied in the same water solution.

Hence, the objective of this study was to evaluate the efficacy of the application of a suspension with two monovalent live attenuated vaccines, PRIMUN SALMONELLA E and PRIMUN SALMONELLA T, to reduce excretion and colonization after an experimental infection with a mixture of two field challenge strains, S. Enteritidis and S. Typhimurium, according to Pharmacopeia instructions.

In conclusion, when the two vaccines (PRIMUN SALMONELLA E and PRIMUN SALMONELLA T) are applied together as a mix in SPF day-old-chicks at a minimum dose, the excretion and colonization of internal organs after a double challenge with S. Enteritidis and S. Typhimurium field strains is significantly reduced.