Controlling Public Health Risks Posed by Zoonotic Pathogens in Beef Cattle Production Through Consumption of Meat Products and Exposure to Environmental Pathways

The contribution of meat animal production (including beef) to the occurrence of human bacterial infections remains a prominent and contentious issue. Currently, the challenge has centered on the accurate identification of the contamination pathways from food animal production to human populations. Evidence shows that the pathogens can be transferred from food animals to human populations through the consumption of contaminated meat products; or via the exposure to livestock and livestock production associated environmental pathways. Therefore, the goal of this research was to determine and evaluate the pathways of pathogen transmission linked to livestock production and to translate the research findings into safety practices for the reduction of human illnesses. In this dissertation, bacterial contamination pathways for beef production chain was first investigated in a farm-to-processing continuum. Then, the fate and transfer of antimicrobial resistant bacteria and genes in the environment associated with beef cattle primary production and manure storage and land application were studied. Finally, public health risks associated with consumption of lettuce that can be potentially contaminated by fertilization manure were estimated. Results showed that the lairage pen environment at the processing plant is of more importance as a contamination source for beef cattle carcasses, compared to animal feces, and pen surface, feed and water sources on the feedlot. The results indicate that cleaning and disinfection of lairage pen environment may potentially reduce the bacterial contamination in beef products. There is no significant evidence demonstrating the linkage between antimicrobial administration in beef cattle and the increase in resistant bacteria and genes in feedlot pen surface materials, manure or in the air/dust nearby. However, beef cattle manure can be a contamination source of antimicrobial resistance in lettuce as soil amendment. To mitigate the contamination originating from manure, our studies showed manure storage as static piles can be considered as candidate intervention strategy, as both antimicrobial resistant bacteria and genes were effectively reduced in manure after a 3-month storage