Evaluation of transfer of maternal immunity to the offspring of broiler breeders vaccinated with a candidate recombinant vaccine against Salmonella Enteritidis

Salmonella Enteritidis (SE) is a major cause of foodborne diseases in humans being frequently related to the consumption of poultry products. Therefore, guaranteeing early immunity to chicks is an important tool to prevent the colonization and infection by this pathogen. The present study evaluated the effectiveness of a candidate recombinant vaccine against SE. Thirty female and five male broiler breeders that were ten weeks-old were divided into 3 groups: unvaccinated (UV), vaccinated with recombinant vaccine candidate (VAC) and vaccinated with commercial bacterin (BAC). Samples of serum and embryonated egg were collected at seven and twelve weeks after the booster dose to quantify the transfer rate of IgY to egg yolks and offspring. Subsequently, forty day-old offspring were divided into two groups (UV and VAC) and challenged on the following day with 107 CFU/chick of SE. Samples of serum, intestine, liver, and cecal content were harvested. Throughout the experiment period, significantly higher levels of IgY were observed in the egg yolk and also in the serum of broiler breeders and offspring of the VAC group in comparison to the UV group. In addition, increased transfer rates of IgY were observed in the VAC group when compared to the BAC group. Furthermore, higher villus-crypt ratios were found out in duodenum, jejunum and ileum at four days post-infection in the offspring from the VAC group. A high challenge dose of SE (107 CFU per chick) was used and despite the stronger humoral immune response provoked by the candidate vaccine, there were no statistical differences in the recovery of viable SE cells from the offspring cecal contents. Therefore, the effect of vaccination to improve intestinal quality may affect the development of the chickens and consequently increase the resistance to lower SE challenge doses.