Listeria is the third-leading cause of death among bacterial foodborne pathogens in the U.S., and pregnant individuals bear a disproportionate share of that risk. Yet the scientific models used to set food safety policy have rarely been designed with pregnant people specifically in mind. A new Michigan State University study to be published in Risk Analysis aims to change that.
Each year, approximately 1,250 Americans contract listeriosis, the illness caused by Listeria monocytogenes. The disease carries a staggering 86% hospitalization rate and is fatal in approximately 14% of cases. For pregnant individuals, the stakes are even higher: pregnancy-associated cases account for 14% of all listeriosis cases, and when listeria reaches the fetus, it causes stillbirth in 25% of those infections. Many pregnant women experience only mild, flu-like symptoms, or none at all, while the bacterium silently crosses the placenta. Recent outbreaks in 2021–23 linked to ice cream, queso fresco and enoki mushrooms resulted in five stillbirths in just three years.
Jade Mitchell, professor in the Department of Biosystems and Agricultural Engineering in the College of Agriculture and Natural Resources, set out to determine how we can better protect pregnant women from Listeria. By analyzing animal studies that tracked how pregnant hosts respond to specific doses of L. monocytogenes, the team developed new models that more realistically show how the body responds to different amounts of a substance. The models — one for maternal infection and one for stillbirth — are built on data from guinea pigs and gerbils, which share key biological traits with humans relevant to how Listeria bacteria cause disease in the body.