Abstract. The objectives of this study were to develop an animal model to study Listeria monocytogenes infection during the peri-parturient period and identify sources of maternal shedding of the pathogen. Peri-parturient mice were infected intragastrically with L. monocytogenes that expressed bacterial luciferase. Mice were then imaged in vivo over time. Secreted breast milk samples from mice infected after parturition were enriched and plated for culture and imaging. Bioluminescence imaging technology was able to detect luciferase emitting L. monocytogenes in vaginal secretions and maternal and fetal organs at 72 and 96 h post infection in mice infected prior to, or just after, parturition. The results from this study clearly show that L. monocytogenes is shed in vaginal secretions and disseminates to the mammary chain, from which it can be shed in the milk of peri-parturient mice.