| Escherichia coli O157:H7 is an important foodborne pathogen and beef cattle represent important reservoirs. E. coli O157:H7 has caused important economic losses to the beef industry and can cause severe illness and death in humans. Pre-harvest interventions have been suggested as a tool to help reduce the occurrence of E. coli O157:H7 associated with beef feedlot cattle. Five clinical trials were conducted to evaluate the effects of Lactobacillus acidophilus strain NPC 747 or an experimental vaccine for reducing the occurrence of E. coli O157:H7 associated with market ready beef feedlot cattle. Feedlot cattle supplemented with 109 CFU daily of NPC 747 were 35% less likely to test positive for E. coli O157:H7 in feces. In an evaluation of dose response and herd immunity to a vaccine, cattle receiving 1, 2, or 3 doses of the vaccine were 68, 67, and 73% less likely to test positive for E. coli O157:H7 in feces compared with external controls. Additionally, vaccinated cattle may have conferred protection to unvaccinated cattle within the same pen, providing evidence for a herd immunity effect. In a second vaccine study, vaccine efficacy for cattle receiving 3 doses of the vaccine was 98.5% when evaluating colonization of E. coli O157:H7 in terminal rectum mucosa (TRM) samples. In two large-scale clinical trials pens of vaccinated cattle were less likely to test positive for E. coli O157:H7 using a novel sampling device (ROPES) and vaccine efficacy was calculated at 76.0% when evaluating colonization of E. coli O157:H7 in TRM samples. NPC 747 and vaccination had no adverse effects on the important feedlot performance outcomes of average daily gain, daily dry matter intake, and feed efficiency. These data support the use of pre-harvest interventions for controlling E. coli O157:H7 in market ready beef feedlot cattle. |
