Location: Meat Safety and Quality
Project Number: 3040-42000-021-004-T
Project Type: Trust Fund Cooperative Agreement
Start Date: May 18, 2020
End Date: May 17, 2021
Objective:
To determine the efficacy of an experimental E. coli O157:H7 subunit cattle vaccine under field conditions.
Approach:
The vaccine field trial will be performed using 300 steers and heifer from the USMARC herd in the USMARC feed yard. The vaccinated group will receive the 2 ml per dose of the experimental E. coli O157 vaccine via the subcutaneous route, in front of the shoulder, on three occasions (Day 0 vaccinations will be administered to the left side of the neck, Day 21 vaccination to the right side of the neck, and Day 42 vaccination will be administered to the left side of the neck.); the control group will be immunized at the same time with Quil A® adjuvant alone. A blood sample of up to 10 ml will be collected from each animal at each collection time point of the study along with a rectal-anal mucosal (RAMS) sampling. RAMS samples will be placed in 5 ml tryptic soy broth (TSB)- phosphate medium (pH 7.2) and transported to the lab for processing. RAMS samples with be vortexed and plated on ChromoAgar for enumeration and prevalence of Shiga toxin-containing Escherichia coli O157:H7 (STEC O157:H7). Presumtive positive colonies will be picked and confirmed to be STEC O157:H7 by Dry-spot and multiplex PCR.
Bacteriological data (pen prevalence data and CFU/g data) will be analyzed using appropriate statistical methods. Treatment (vaccine) effects will be determined at the pen-level (for prevalence data) and the individual animal level (for CFU/g data) using generalized linear mixed models (GLMM). For all models, pen will be assigned as a random effect. Independent variables will include treatment (vaccination), time, and treatment x time interactions.
