Transmission routes for Salmonella Dublin infection in cattle

Clinically affected cattle and latent carriers shed Salmonella Dublin to the environment under conditions of stress, primarily in the peripartum period. Once S Dublin is shed in feces and secretions (saliva, colostrum, and milk), it can survive in the environment. A newborn calf may become infected via the oral route at calving or by consuming raw colostrum or milk from an infected cow. The infected calf then sheds the bacterium to the environment, where susceptible calves ingest it through direct contact or fomites (contaminated surfaces or objects).

In addition, intrauterine infection of the fetus (vertical transmission) in the last trimester of gestation can result in abortion or birth of an infected calf.

Zoonotic infection occurs mainly in caretakers working with clinically affected cattle and latent carriers at calving. Humans become infected with S Dublin via contact with feces and secretions during calving assistance, equipment or facility cleaning, raw colostrum and milk manipulation, or close contact with sick cattle.