A study by Michigan State University researchers may lead to better prevention practices to limit E. coli bacteria transmissions. The study, published in Applied and Environmental Microbiology, involved the collaborative effort from the university’s veterinarians, animal scientists, epidemiologists, microbiologists, graduate students, undergraduates and farmers. “It would have been extremely difficult to do this study without such a wide range of expertise,” said Shannon Manning, Ph.D., molecular biologist and principal investigator of the study. Specifically, the study found that dairy cattle under stress from hot weather and energy loss from milk production were significantly more likely to shed Shiga toxin-producing Escherichia coli (STEC), a type of E. coli that can cause serious illnesses in humans through the production of a potent toxin. This new finding, according to the university, provides an opportunity for targeting prevention practices to reduce the prevalence of these potentially deadly strains of E. coli, which cause about 100,000 illnesses, 3,000 hospitalizations and 90 deaths annually in the United States. “Most importantly, our study involved cattle farmers who were willing to be involved in projects that help to improve the safety and quality of the food they produce,” said Daniel Grooms, DVM, Ph.D., Dipl. ACVIM, large animal veterinarian and a collaborator in the study. The study sampled more than 1,000 cattle from six dairy farms and five feedlots in Michigan. Fecal samples were obtained from each animal and cultured for STEC. The prevalence of STEC was higher in beef versus dairy cattle with considerable variation across herds, according to the study’s findings. Dairy cattle were significantly more likely to shed STEC when the average temperature was >28.9°C one to five days prior to sampling, during their first lactation, and when they were <30 days in milk. These data, according to the researchers, suggest that the stress or the negative energy balance associated with lactation may result in increased STEC shedding frequencies in Michigan during the warm summer months. Future prevention strategies aimed at reducing stress during lactation or isolating high-risk animals could be implemented to reduce herd-level shedding levels and avoid transmission of STEC to susceptible animals and people, the researchers concluded. “Reducing STEC colonization and shedding in cattle can decrease the likelihood of these bacterial pathogens from entering the food supply and causing foodborne infections in people,” Dr. Manning said. “By understanding specific factors that increase the risks of STEC shedding in cattle, new management strategies, such as the isolation of high-risk animals, can be developed to limit transmission.” The researchers now plan to exam the diversity of different STEC strains that are shed as well as determine the rate at which animals acquire new STEC strains over time. “We hope to assess how frequently individual animals acquire different types of STEC and determine which types are most commonly linked to disease in humans,” Manning said.
