When are chickens most susceptible to infection with Salmonella enteritidis?

• A. Young (<3 weeks)
• B. Laying hens
• C. During molting
• D. Senior birds

Answer: (A)

Young chicks are most susceptible because their immune system and gut defenses are still immature. In birds under three weeks old, the intestinal barrier and innate immune responses aren’t fully developed, so Salmonella enteritidis can more easily colonize the gut and potentially spread systemically before robust adaptive immunity can respond. Maternal antibodies may offer some help, but they often aren’t enough to prevent early colonization in neonates. As birds age, their gut microbiota becomes more established and their immune system matures, reducing the likelihood of initial colonization. While infection can occur at any age, the risk is highest in the earliest life stage, making the period under three weeks the window of greatest susceptibility.