Effect of Salmonella enterica serovar Enteritidis infection on egg production and immune response of the laying duck

Laying rate and egg quality are also decreased after SE infection (<i>P</i>&lt;0.05). We further show that SE readily colonizes the stroma, small follicle, isthmus, and vagina in the reproductive tracts of susceptible ducks. Analysis of immune responses revealed that immunoglobulin (IgA, IgG, IgM) is higher in susceptible than in resistant ducks (<i>P</i>&lt;0.05), whereas T lymphocyte subpopulations (CD3⁺, CD4⁺, CD8⁺) display the opposite trend. Expression profiles of immune response genes were also investigated in the reproductive tract of SE-infected ducks using qRT-PCR analysis, revealing that a number of immune genes, including toll-like receptors (TLR2, TLR4-5, TLR15, TLR21), NOD-like receptors (NOD1, NLRX1, NLRP12), avian β-defensins (AvβD4-5, AvβD7, AvβD12), cytokines (IL-6, IL-1β, IFN-γ), and MyD88 are upregulated in the reproductive tracts of SE-infected ducks (all <i>P</i>&lt;0.05), whereas TLR3, TLR7, NLRC3, NLRC5 and TNF-α are significantly downregulated in these animals.